Submarine geology and geophysics

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90:2018 Larsen, B. and K. Fytianos, 1989. OrganocMorine compounds and PCB congeners in contaminated sediments [of Thermaikos Gulf, N Greece]. Sci. total Environment, 86(3):273-279. Environ. Inst., Radiochem. Div., Joint Res. Ctr. of the European Comm., Ispra (Va), Italy. 90:2019 Mishukov, V.F. and Ye.A. Sokolov, 1988. Secondary pollution of seawater by organic peroxides. Oceanology (a translation of Okeanologiia), 28(4):449-453. Pacific Oceanol. Inst., Far Eastern Sci. Ctr., Acad. of Sci., Vladivostok, USSR. 90:2020 Nishikawa-Kinomura, K.A. et al., 1988. Marine pollution in the central southern California Bight adjacent to the American-Mexican border zone. Revue int. Oc~anogr. M~d~ 91-92:125-150. CICES, Ensenada, BC, Mexico. 90:2021 Rocrden, O. and K. Reisinger et al., 1989. A simple clean-up procedure for the quantitative determination of PCBs in complex materials. Z. analyt. Chem, 334(5):413-417. Reisinger: Inst. of Appl. Phys. Chem., Nuclear Res. Ctr. (KFA) Julich, P.O. Box 1913, D-5170 Julich, FRG.

90:2024 Vogt, N.B. and C.E. Sjoegren, 1989. Investigation of chemical and statistical methods for oil-spill classification. Ana~,tica chim. Acta, 222(1):135150. Fluorescence spectrometry, infrared spectrometry, liquid chromatography with ultraviolet detection, and gas chromatography with flame ionization (GC/FID) or mass spectrometric (GC/MS) detection are investigated for possible use in oil-spill identification. The discriminating power of these five procedures is determined for 23 oils fr..,m four geographic regions. The multivariate SIMCA method is shown to increase the discriminating power of the data compared to the univariate methods. The ranking indicates that fluorescence spectrometry, selected peak-area ratios from GC/FID, S, Ni and V contents, and selected GC/MS peak ratios are useful for classification of oils. Str. for lndustriforskning, Postbocks 350, Blindern, N-0314 Oslo 3, Norway.

C240. Corrosion 90:2025 Mansfeld, F., B. Little (comment) and S.C. Dexter (reply), 1989. Discussion on 'Effect of seawater biofilms on corrosion potential and oxygen reduction of stainless steel' lby S.C. Dexter and G.Y. Gao]. Corrosion, 45(10):786-789.

90:2022

Saad, M.A.H., 1988. Status of suspended matter, total residue, fixed total residue and volatile matter in the waters of three heavily polluted canals of the Shatt al-Arab Estuary at Basrah, lraq. Revue int. Oc~anogr. M~d, 91-92:87-103. Oceanogr. Dept., Alexandria Univ., Moharem Bey, Alexandria, Egypt.

90:2026 Pao, P.S. et al., 1989. Comparison of corrosion-fatigue cracking of AI-Li alloy AA 2090-T8FA 1 and alloy AA 7075--T651 in salt water. Corrosion, 45(7): 530-535. Naval Res. Lab., Code 6303, Washington, DC 20375-5000, USA.

90:2023 Talbot, Victor, 1989. Mobility and speciation of cadmium and lead in polluted seawater of Port Phillip Bay, Australia: management implications. J. coast. Res, 5(4):755-763. 60 Vincent St., Nedlands, WA 6009, Australia.

90:2027 Smith, S.W., K.M. McCabe and D.W. Black, 1989. Effects of flow parameters on the cathodic protection of a steel plate in natural seawater. Corrosion, 45(10):790-793. Dept. of Ocean Engng, Florida Atlantic Univ., P.O. Box 3091, Boca Raton, FL 33431-0991, USA.

D. SUBMARINE GEOLOGY AND GEOPHYSICS D10. Apparatus and methods 90:2028 Cao, Shunhua and B.L.N. Kennett, 1989. Reflection seismograms in a 3-D elastic model: an isochronal

approach. Geophys. J. int~ 99(1):63-80.

The reflection and diffraction of elastic waves by surfaces in three dimensions and scattering by thin scatterers can be combined in a common formu-

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D. SubmarineGeologyand Geophysics

lation derived by using an integral formulation of the elastic wave field together with ray approximations for wave propagation between source or receiver and reflecting surface or scatterer. The method is illustrated by calculation of P-P reflections for a seismic line oblique to an anticline and for a variety of parameter contrasts for a simple scatterer model. The facility to calculate theoretical seismograms for both surface reflections and scattering is exploited to look at the reflection from the crust-mantle boundary in three dimensions. Res. School of Earth Sci., The Australian Natl. Univ., GPO Box 4, Canberra, ACT 2601, Australia. 90:2029 Cobo-Parra, P. and C. Ranz-Guerra, 1989. Direct and inverse problems in layered sea bottoms including attenuation: synthetic data. Acustica, 69(2):81-87. Application of the convolutional model to highresolution acoustic exploration of a layered sea bottom is examined using a direct approach with an established sea bottom and an indirect approach with a known reflection response. For the direct problem the impulse response from the bottom is computed from the interface reflection coefficient and then convolved with the attenuation response and sonar pulse to obtain a reflection response. Solution of the indirect problem includes deconvolution of the input sonar pulse waveform and inversion of the reflection response. Results obtained using a four-layered synthetic bottom are presented. Inst. de Acustica, Serrano, 144, 28006 Madrid, Spain. (hbf) 90:2030 Crampin, Stuart, 1989. Suggestions for a consistent terminology for seismic anisotropy. Geophys. Prospect, 37(7):753-770. Seismic anisotropy is an unfamiliar concept to many geophysicists ,and the use of misleading and ambiguous terminology has made it more difficult to understand. I suggest here a consistent terminology in which simple expressions have specific meanings similar to their colloquial meanings. This is not a manual of anisotropy, and is not intended for theoreticians; it is a list of terms which may make anisotropy a little easier to understand for those more familiar with wave propagation in isotropic solids. British Geol. Surv., Murchinson House, West Mains Rd., Edinburgh EH9 3LA, Scotland, UK. 90:2031 Murray, C.N., D.A. Stanners and M. Jamet, 1989. A piston corer .for recovery of deep ocean sediments under pressure. Mar. Geotechnol~ 8(1):69-80.

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A corer has been developed, which upon recovery maintains the hydrostatic pressure within the section sampled. The corer consists of a piston corer of classical design, a pressure retaining module sealed at both ends by high-pressure self-cleaning valves, and an acoustic control system that has been tested successfully in the field. The maintenance of pressure is critical for geochemical studies of deep ocean processes affecting the distribution and dispersion of heavy metals and radionuclides. Comm~ of European Communities, Joint Res. Ctr., Ispra Establishment, Ispra, VA, Italy. (hb0 90:2032 Ostrovsky, A.A., 1989. On the nature of microsbocks recorded by ocean bottom seismographs. Mar. geophys. Res, 11(2):113-118. Results of the study of microshocks which constitute a specific type of noise on the records of ocean bottom seismographs are given. Various possible causes of their origin have been analysed. The great majority of microshocks are produced by external causes: bottom displacements under an instrument at the deployment site and the mechanical action of marine organisms on OBSs. The use of parallel recording at two seismometers some distance apart is suggested. P.P. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, Krasikova 23, USSR. 90:2033 Ostrovsky, A.A., 1989. The estimation of ocean bottom seismographs' coupling characteristics by means of microshock recordings. Mar. geophys. Res, 11(2):119-127. A transient technique was used for estimating the bottom-instrument response function in OBS experiments in deep ocean. Sharp mechanical impacts on a bottom seismograph, usually induced by bottom displacements under the instrument, are suggested as rough analogues of the impulses for the bottominstrument system transient calibration. Microshocks usually have sufficiently small duration to be used for coupling characteristics estimates. Test measurements have shown that this method makes it possible to distinguish spectral features characterising earthquakes and seismic noise wavetrains from those caused by coupling resonances of the OBSsediment interface. P.P. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, Krasikova 23, USSR. 90:2034 Poupinet, G. et al., 1989. A seismological platform transmitting via METEOSAT. Bull. seism. Soc. Am, 79(5):1651-1661. A portable seismological station that transmits

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seismograms through METEOSAT has been built and is being tested in different applications: monitoring local seismicity in mountainous regions and on a volcano and recording distant earthquakes in zones of difficult access. Despite limitations in transmission capacity, seismological data collection platforms will help to monitor regions where there are no permanent networks. Operation of satellite collected seismological networks will be greatly improved when space agencies transmit the time of reception of messages with millisecond precision. LGIT, Univ. Joseph Fourier, BP 53X, F 38041 Grenoble, France.

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waves. Wherever there exists relative motion between the seabed and water, an exposed OBS is subject to 'added mass' forces that cause it to move with the water rather than the sediments. Calculations based on measured seabed motions show that a neutral density, buried seismometer has superior sediment coupling characteristics to any exposed OBS design. Geo-Aeoustics Lab., RSMAS, Univ. of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149, USA.

D40. Area studies, surveys, bathymetry 90:2035

Rocca, F., C. Cafforio and C. Prati, 1989. Synthetic aperture radar: a new application for wave

equation techniques. Geophys. Prospec& 37(7): 809-830. We show how the techniques of downward continuation and imaging invented for seismic waves can be applied to electromagnetic surveys conducted with synthetic aperture radar. The algorithms used closely follow those used for seismic waves. Differences are induced by alternate wavelengths, wave velocities, distances between sources and reflectors, etc. We analyse in detail a survey carried out using a satellite; difficulties arise because the satellite's orbit cannot be approximated by a simple straight line if the spatial resolution of the survey is high. We determine appropriate techniques for the correction of the distortion induced by the latter, delimit the resolution of the observed data, as seen from a satellite, and show examples of the application of the technique of seismic migration to satellite data. Dipart. di Elettron., Politec. di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy. 90:2036

Stanley, C.R. and J.K. Russell, 1989. PEARCE. PLOT: a Tarbo-Pascal program for the analysis of rock compositions with Pearce element ratio diagrams. Computers, Geosciences, 15(6):905-926. Dept. of Geol. and Geophys., Univ. of Calgary, AB T2N IN4, Canada. 90:2037

Trevorrow, M.V. et al., 1989. Very low frequency, ocean bottom ambient seismic noise and coupling on the shallow continental shelf. Mar. geophys. Rest 11(2):129-152. Sources of very low frequency ambient seismic noise in shallow water continental margin sediments are investigated using Ocean Bottom Seismometers (OBS). Predominant seismic motions are due to surface gravity waves and water-sediment interface

90:2038

Babb, R.J., 1989. Feasibility of interferometric swath bathymetry using GLORIA, a long.range sidescan. I E E E Jl ocean. Engng, 14(4):299-305. The feasibility of adding an interferometric swath bathymetry system to GLORIA is discussed. The size of the low-frequency transducer arrays and towfish precludes significant modifications, but even without such changes bathymetric errors could be several tens of meters over a usable swath somewhat smaller than the normal GLORIA swath. The effect of interfering acoustic paths either scattered or reflected from the sea surface is not too serious except at short ranges or under exceptionally calm sea conditions. Many of the results should be applicable to other similar systems. Inst. of Oceanogr. Sci., Deacon Lab., Godalming, Surrey GU8 SUB, UK. 90:2039

Beiersdof, H e l m ~ and Jrrg Erzinger, 1989. Observations on the bathymetry and geology of the northeastern Manihiki Plateau, southwestern Pacific Ocean. S. Pacif. mar. geol. Notes, U.N, Suva, 3(4):33-46. An area of 1800 km 2 on the northeast slope of the Manihiki Plateau was surveyed using a multibeam echosounder, a subbottom profiler, dredges, and corers. The basaltic basement and overlying 260-m thick volcaniclastic sequence were also cored at DSDP Site 317. The thickness and areal distribution of the volcaniclastic sediment suggest that significant explosive events took place here during the Early Cretaceous. Two ENE-trending canyons, 12-kin long and 300-m deep, seem to have resulted from block faulting of the basement. Bundesanstalt fur Geowiss. und Rohstoffe, Stilleweg 2, 3000 Hannover 51, FRG. 90:2040

Briggs, K.B., 1989. Microtopographical roughness of shallow-water continental shelves. I E E E Jl ocean.

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D. Submarine Geology and Geophysics

Engng. 14(4):360-367.

High-resolution roughness height measurements were made of the seafioor at seven locations on continental shelf sediments in water depths ranging from 18 to 50 m. The data show the rms roughness height varying from 0.3 to 2.3 em for fiat, featureless bottoms and rippled bottoms, respectively. Correlation lengths of different bottom types were estimated by using the Wiener-Khintchine theorem and examining the low-frequency behavior of the roughness spectra derived from the longest roughness profiles. Oceanogr. Div., NORDA, Code 333, Stennis Space Ctr., MS 39529, USA.

90:2041 Denbigh, P.N., 1989. Swath bathymetry: principles of operation and an analysis of errors. I E E E J! ocean. Engng, 14(4):289-298. The principles of swath bathymetry are described, and the main cause Of depth error is identified as acoustic interference, particularly from the sea surface. An error analysis is presented which gives the relationship among depth errors, the signalto-interference ratio, the grazing angle, receiver spacing, and area resolution. It enables a prediction of when its measurement of depth can meet the accuracies required for nautical charting. School of Engng and Appl. Sei., Univ. of Sussex, Falmer, Brighton, Sussex BNI 9QT, UK.

90:2042 Goff, J.A. and T.H. Jordan, 1989. Stochastic modeling of seafloor morphology: resolution of topographle parameters by Sea Beam data. I E E E J i ocean. Engng, 14(4):326-337. Stochastic methods of analysis are used to delineate stochastic seafioor provinces, which can be related to geological variables such as spreading rate and age. The resolving power of an inversion algorithm, which estimates five parameters of seafloor covarlance function' from a single swath of multibeam echosounding data, is evaluated as a function of swath length, orientation of ship track with respect to topographic grain, and response width of the sounding system. The experiments show that resolution of the covariance parameters is strongly dependent on the number of sampled characteristic lengths (width of covariance function in the shiptrack direction). Dept. of Earth, Atmos. and Planetary Sci., MIT, Cambridge, MA 02139, USA.

90:2043 Herzfeld, U.C., 1989. Geostatistieal methods for evaluation of Seabeam bathymelric surveys: case studies of Wegener Canyon, Antarctica. Mar.

315

Geol., 88(1-2):83-95.

Case studies in applications of the universal kriging method of geostatistics to bathymetrie data are described, and the resultant large-scale maps presented. The advantages of the method applied include a detailed morphological representation of the seafloor, even in areas with survey gaps, and the possibility of solving specific questions via variogram alteration. A measure of map precision is provided without additional computing effort. Suggestions for survey optimization are given. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA.

90:2044 Herzfetd, U.C., 1989. Variography of submarine morphology: problems of deregularization, and cartographical implications. Mathl Geol, 21(7): 693 -713. Bathymetric surveys were made in the Weddell Sea, and geostatistical methods were applied in the Seabeam postprocessing. Variographie investigations necessary to the eartographical-geomorphological evaluation shed new light on classical geostatistical concerns. Seabeam data provide a good example of a mean square, dilferentiable regionalized variable, where data are sampled over a 2-D support. By deregularizatious of the sample variograms, spatial continuity can be shown to be a property of seafloor depth as weU as a point variable. The results are discussed in a sedimentological context, and largescale kriged bathymetrie maps are presented. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA.

90:2045 Kamgar-Parsi, Behrooz et al., 1989. Toward an automated system for a correctly registered bathymetric chart. I E E E Jl ocean. Engng, 14(4): 314-325. To chart the ocean floor, a ship sails for several miles along a straight track and collects a swath of depth data. Because each swath of data overlaps with several others, registration is performed both at local and global levels. The 'primitives' used for local matching are contours of constant depth which are extracted from the data and are represented as a modified chain code. The main heuristic guiding the search for matching contours of equal depth is their proximity to the middle of the apparent (unregistered) overlapping region. The degree to which two contours match is determined by the correlation of their respective chain codes and the geometrical proximity of their nodes. All 'best' matches are considered tentative until their geometrical implications are evaluated and a consistent majority has emerged. To do global matching, a cost function is

316

D. Submarine Geology and Geophysics

constructed and minimized. Terms contributing to the cost include violation of local matches as well as the compression and bending of the swaths of data. Ctr. for Appl. Res. in Artificial Intell., Naval Res. Lab., Code 5511, Washington, DC 20375, USA. 90:2046 Malinverno, Alberto, 1989. Segmentation of topegraphic profiles of the seafloor based on a seff-affine model. IEEE Jl ocean. Engng, 14(4): 348-359. Profiles of seafloor topography can be statistically described as a self-affine stochastic time series characterized by a correlation parameter (the spectral exponent related to the fractal dimension) and an amplitude parameter (an index of dispersion of first differences). This characterization provides a simple quantification of 'roughness" of topography. The profiles are automatically subdivided into statistically homogeneous segments and parameters are measured on each segment. The segments are then grouped into classes with similar statistical parameters. The method is applied to profiles of the seafloor in the vicinity of the axis of the Explorer Ridge, NE Pacific Ocean. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA. 90:2047 Smith, D.K. and P.R. Shaw, 1989. Uslng topographic slope distributions to infer seafloor patterns. IEEE Jl ocean. Engng, 14(4):338-347. A method is described for obtaining parameters for the distribution of slopes in a region of abyssal hills from Sea Beam swath bathymetry. The azimuthal distribution of vectors normal to small patches of seafloor provides a first-order indication of dominant elongation directions in the topography and the distributions of dip angles within a small window centered on peal[s of the azimuthal density function provide an indication of any asymmetry in average cross-sectional shapes of features. Results are presented for the application of the method to three regions in the northeast Pacific Ocean and two regions in the southwest Indian Ocean. Dept. of Geol. and Gcophys., WHOI, Woods Hole, MA 02543, USA. 90:2048 Vyas, N.K. and H.I. Andharia, 1988. Coastal bathymetric studies from space imagery. Mar. Geod, 12(3):177-187. Panchromatic satellite imagery acquired by SPOT over the Bay of Bengal is used to analyze the

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refraction of coastal gravity waves and from this analysis to estimate coastal water depths. "The resulting estimates, when compared with standard bathymetric charts, were found to be in agreement up to a depth of 30 m, with an r.m.s, error of 2.6 m. The method seems useful for remotely sensed bathymetric work; however, further research is required to reduce the error margin and to operationalize the method.' MOD, RSAG, RSA Space Applications Ctr., Ahmedabad-53, India. (emm)

D60. Geomorphology (fans,

canyons, etc.)

90:2049 Blumsack, S.L. and G.L. Weatherly, 1989. Observations of the nearby flow and a model for the growth of mud waves. Deep-Sea Res, 36(9A): 1327-1339. Observations over an 1 l-month period are described in a region of mud waves in the central Argentine Basin. The mud waves are neither aligned with nor perpendicular to the mean current. An extension of a simple lee wave model indicates that certain mud waves are (linearly) unstable due to preferential deposition at the crests and erosion of the troughs. The most unstable mud waves have wavelengths and orientations consistent with observations. Dept. of Math., Florida State Univ., Tallahassee, FL 32306, USA.

90:2050 Cochonat, P., G. Ollier and J.L. Michel, 1989. Evidence for slope instability and current-induced sediment transport, the RMS Titanic wreck search area, Newfoundland Rise. Geo-Marine Lefts, 90): 145-152. The first map of the sea bed morphology and sedimentary features within the search area is proposed from the interpretation of SAR side-scan sonar images. Downslope sedimentary features such as erosional furrows and crown scarps constitute a 7-kin-wide instability corridor. A large field of asymmetrical sediment waves indicating a downslope transport is identified. Current-induced features corresponding to associated sand ribbons and barehan dunes resulting from the Western Boundary Undercurrent action are mapped. Finally, the origin of the sea bed features is discussed in an attempt to link each bed form to a sedimentary process. IFREMER, Ctr. de Brest, BP 70, 29263 Plouzane, France.

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D. Submarine Geology and Geophysics

D70. Coasts, beaches, marshes 90:2051 Bouma, A.H. et al., 1989. Influence of relative sea level changes on the construction of the Mississippi Fan. Geo-Marine Letts, 9(3):161-170.

A conceptual sea-level-driven depositional model for individual fanlobes of the Mississippi Fan does not permit direct application of the sequence stratigraphic principles of Vail and colleagues. DSDP Leg 96 results suggest that, during initial relative lowering of sea level, the canyon and upper fan channel were formed; excavated fine-grained slope sediments may have formed a debris flow deposit base for the faD.lobe. Continued lowering produced constructional channel-levee-overbank deposits. Rising relative sea level inhibited input of coarse elastics, and channel depressions filled with muds. A blanket of 0temi)pelagics represents relative high sea level stand. School of Geosci. and Dept. of Geol. and Geophys., Louisiana State Univ., Baton Rouge, LA 70803, USA. 90:2052 Bricker-Urso, S. et al., 1989. Accretion rates and sediment accumulation in Rhode Island salt marshes. Estuaries, 12(4):300-317. Grad. School of Oceanogr., Univ. of Rhode Island, Narragansett, RI 02882, USA. 90:2053 Cahoon, D.R. and R.E. Turner, 1989. Accretion and canal impacts in a rapidly Sl~idin~ wetland [Louisiana coast]. II. Feldspar marker horizon technique. Estuaries, 12(4):260-268. Louisiana Geol. Survey, P.O. Box G, Univ. Station, Baton Rouge, LA 70893, USA. 90:2054 Carter, R.W.G. et al., 1989. Barrier and lagoon coast evolution under differing relative sea-level regimes: examples from Ireland and Nova Scotia. Mar. Geol. 88(3-4):221-242.

In Ireland, recent sea-level rise has been limited to < 1 mm/yr. The Atlantic coast of Nova Scotia has been experiencing sea-level rises up to three to five times greater. In Ireland, barrier-lagoon form is controlled by local basement expression, particularly through the emergence of headlands and the requirement to maintain cross-shore drainage, which leads to a four-fold categorization of Irish barriers and lagoons, from freshwater seepage to open tidal environments. The Nova Scotian examples are associated with rapidly moving erosional fronts, with local basement control relegated to a subordinate rote at the expense of rapid changes in sediment

317

supply. Barriers can both grow and decay under these conditions, simultaneously forcing development and destruction of adjoining lagoons. These major differences also find expression in sedimentary sequences. Dept. of Environ. Studies, Univ. of Ulster, Coleraine, Co. Derry BT52 ISA, Northern Ireland. 90:2055 Dayton, P.K. et al., 1989. Unusual marine erosion in San Diego County from a single storm. Estuar. coast. Shelf Sci, 29(2):151-160. Scripps Inst. of Oce.anogr., La Jolla, CA 92093, USA. 90:2056 DeLaune, R.D. et al., 1989. Accretion and canal impacts in a rapidly subsiding wetland lLouisiana coast|. I. t~Cs and z~*Pb techniques. Estuaries, 12(4):247-259. Ctr. for Wetland Resour., Louisiana State Univ., Baton Rouge, LA 70803-751 I, USA. 90:2057 Duffy, William, D.F. Belknap and J.T. Kelley, 1989. Morphology and stratigraphy of small barrierlagoon systems in Maine. Mar. Geol~ 88(34):243-262.

The coast of Maine contains over 200 barrier-lagoon systems, most quite small, with an aggregate length of nearly 100 kin. Geomorphic forms include barrier spits, pocket barriers, double tombolos, and cuspate and looped barriers. The few long sandy beaches are mostly barrier spits; the remainder of barriers are composed p~marily of gravel or mixed sand and gravel. Normal wave action, coarse-grain size, and a deeply embayed coast result in steep reflective profiles several meters above MHW. Occasional storm events build lobate gravel fans along the landward margin, but the presence or absence of a tidal inlet is of paramount importance in shaping the Holocene stratigraphy of the back barrier region. Dept. of Geol. Sci., Univ. of Maine, Orono, ME 04469, USA. 90:2058 Dunayev, N.N. and H. Foyo-Herrera, 1988. Geological and geomorphological ~ and neotectonics of Icacr Peninr (Cuba) and its western shelf. Oceanology (a translation of Okeanologiia), 28(4):461-464.

The relief of the shelf and adjoining land is largely governed by erosional, karst, reef-development and wave processes taking place in regressive and transgressive epochs of Late Quaternary time. Some areas of the shore zone exhibit abrasional development, promoted by the fact that mechanically

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weak calcarinite layers dip toward the land and by a deficiency of beach-forming material as a result of the depressed state of the benthos that forms its main source. It is suggested that pebble-gravel material derived from rocks similar to those making up the coastline be used as fill to stabilize the shoreline. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. 90:2059 Dyer, K.R., 1989. Sediment processes in estuaries: future research requirements. J. geophys. Res, 94(CI0): 14,327-14,339.

Gaps in current understanding of the erosion, transport and deposition of sediment in estuaries are briefly reviewed. It is concluded that future work should give priority to (I) the formation, movement and entrainment of high concentration near bed layers; (2) particle interactions, including flocculation, cycling processes, and chemical and biological interactions; (3) intertidal mudflat processes, sediment exchanges in shallow water and wave induced mud transport; (4) development of improved parameterization of exchange processes for inclusion in 3D mathematical models; and (5) development and use of new instrumentation for field measurements, especially of intermittent and long term events. Inst. of Mar. Studies, Plymouth Polytechnic, Drake Circus, Plymouth, Devon, PL4 8AA, UK. 90:2060 Grabemann, I. and G. Krause, 1989. Transport processes of suspended m i l e r derived from time series in a tidal estuary. J. geophys. Res., 94(CI0): 14,373-14,379.

Optical beam transmittance meters integrated into Aanderaa current meters were used to measure long time series of suspended matter concentration simultaneously with current velocity and salinity in the turbidity maximum of the Weser Estuary. They cover the spectrum from I0 rain to several months. Analyses demonstrate that the tidal dynamics of deposition into and resuspension of particles from temporally and spatially limited material sources at the bottom is the dominant process in the turbidity maximum, while the nontidal gravitational circulation acts as a long-term source and sink. There is a remarkable repeatability of concentration patterns during similar discharge conditions. GKSS Res. Ctr. Gcesthacht, Max Planck Str., D-2054 Geesthacht, FRG. 90:2061 Holtedahl, Hans, 1989. Submarine end moraines and associated deposits off the south coast of Norway.

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Mar. Geol, 88(1-2):23-48. Univ. of Bergen, Geol. Inst., Avd. B, AIIegt. 41, N-5000 Bergen, Norway.

90:2062 Jorgensen, N.O., 1989. Holocene methane-derived, dolomite-cemented sandstone pillars from the Kailegat, Denmark. Mar. Geol, 88(1-2):71-81.

Dolomite-cemented sandstone pilars up to 4 m high and 1 m in diameter are recorded from 10-12 m of water in the Kattegat, Denmark. The carbon isotopic signature of the dolomite cement displays negative ~3C values in the range of -44 ppt to -40 ppt, suggesting that the dolomite derived its carbon via methane oxidation. It is believed that the methane originates from shallow gas in Late Quaternary marine deposits and that the dolomite precipitation took place as a result of anaerobic methane oxidation. Inst. of Hist. Geol. and PaleontoL, Univ. of Copenhagen, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark. 90:2063 Kimberley, M.M., 1989. Fitting a iog~thm|c spiral tO the shoreline of a headland-bay beach. Computers, Geosciences, 15(7):1098-1108. Dept. of Mar., Earth, and Atmos. Sci., North Carolina State Univ., Raleigh, NC 27695-8208, USA. 90:2064 Kjerfve, BjSrn and K.E. Magill, 1989. Geographic and hydrodynamic characteristics of shallow coastal lagoons. Mar. Geol, 88(3-4):187-199.

Coastal lagoons can be conveniently separated based on geomorphology into leaky, restricted or choked systems according to water exchange with the coastal ocean. Leaky systems have the shortest turnover time; choked lagoons, the longest. In leaky coastal lagoons, oscillating tidal currents account for most of the flow variance and mask residual currents due to wind- and freshwater-induced density gradients. In restricted lagoons, tides, winds, and freshwater runoff drive components of the circulation. Winds usually dominate mixing in choked lagoons, and water exchange with the coastal ocean largely depends on the hydrologic cycle. Coastal lagoons are usually well mixed, but can exhibit significant horizontal gradients. In general, river inflow and heat balance induce stratification in coastal lagoons, whereas winds and tides cause mixing. Belle W. Baruch Inst. for Mar. Biol. and Coastal Res., Univ. of South Carolina, Columbia, SC 29208, USA.

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D. Submarine Geology and Geophysics

90:2065 Knaus, R.M. and D.L. Van Gent, 1989. Accretion and canal impacts in a rapidly subsiding wetland [Louisiana coast]. HI. A new soil horizon marker method for measuring recent accretion. Estuaries,

12(4):269-283. Nuclear Sci. Ctr., Louisiana State Univ., Baton Rouge, LA 70803, USA. 90:2066 Kostaschuk, R.A., M.A. Church and J.L. Luternauer, 1989. Bedfonns, bed material, and bedload transport in a salt-wedge estuary: Fraser River, British Columbia. Can. J. Earth Sci, 26(7):14401452. The lower main channel of the Fraser River is a sand-bed, salt-wedge estuary. Bed-material composition remains consistent over the discharge season and long term. Changes in bedform height and length follow but lag seasonal fluctuations in river discharge. A strong, direct, but very sensitive relationship was found between bed load and river discharge. Bedload transport in the estuary appears to be higher than upstream, possibly because of an increase in sediment movement along the bed to compensate for a reduction in suspended bedmaterial load produced by tidal slack water and the salt wedge. Dept. of Geogr., Univ. of Guelph, ON N I G 2Wl, Canada. 90:2067 Lang, G. et al., 1989. Data interpretation and numerical modeling of the Mud and Suspended Sediment Experiment 1985. J. geophys. Res~ 94(C10): 14,381-14,393. Measurements obtained during a field survey in a 30-km-long section of the Weser Estuary (northern Germany) were used together with numerical simulations of a 3-D finite difference model to arrive at a better understanding of the hydrodynamics and transient and spatial dynamics of the turbidity maximum in the estuary. Detailed analyses demonstrate a clbse relationship between local nearbottom velocity gradient, stratification, and turbulence on the one hand and suspended sediment concentration on the other. A comparison between numerical results and measured data lead~ to improved parameterization of bottom shear stress, wherein bottom shear stress is calculated from near-bottom Reynolds stress, with consideration of the stratification. Inst. fur Stromungsmech. und Elek. Rechnen im Bauwesen, Univ. Hannover, Appelstr. 9a, 3000 Hannover 1, FRG. 90:2068 Liu, Kofei and C.C. Mei, 1989. Effects of waveinduced friction on a muddy seabed modelled as a

319

Bingham-plasfie fluid. J. coast. Res, 5(4):777-789. Fluid mud found at the bottom of some estuaries and coastlines contains a high concentration of clay particles. In this paper we focus on the Binghamplastic behavior known to exist in estuary and river mud with high clay concentration. By including interracial friction, motion in a thin mud layer induced by a solitary wave propagating in a much thicker layer of overlying water is analyzed. Effects of the mud motion on wave damping is then calculated for both horizontal and sloping sea beds. Dept. of Civil Engng, MIT, Cambridge, MA 02139, USA. 90:2069 Long, Bernard et al., 1989. Geometry of a deltaic lobe in regressive context. Bull. Cent. Rech. Explor.Prod. Elf-Aquitaine, 13(1):189-213. (In French, English abstract.) Inst. Natl. de la gech. Sci., 310 ave. des Ursulines, Rimouski, PQ G5L 3AI, Canada. 90:2070 Long, Bernard and Nathalie Ross, 1989. Review and classification of nearshore bars. Bull. Cent. Rech. Explor.-Prod. Elf-Aquitaine, 13(1):175-187. (In French, English abstract.) Sedimentary structures described as nearshore bars are reviewed. A classification is proposed which recognizes six genetic groups of bars, generally formed in microtidal or mesotidal environments, th~it are defined by their formation as a result of wind-generated progressive waves or edge waves near the sh"ore. Type six, a product of both progressive-wave and edge-wave action, appears to be the most stable common type. INRS-Oceanol., 310 Allee des Ursulines, Rimouski, PQ G5L 3A1, Canada. 0abf) 90:2071 Ludwick, J.C., 1989. Bed load transport of sand mixtures in estuaries: a review. J. geophys. Rest 94(C10): 14,315-14,326. The fundamental inhomogeneity of estuaries is evident in their irregular boundaries, waters of varying density, fluid motions that arise from multiple unsteady forcings, and sediments of various grain sizes. Reviewed here is the influence of mixed particle size on the transport of sand as bed load. Investigators commonly assume a reference transport function (RTF) which is any established formulation for the flux of bed load under steady unidirectional flow over a substrate of monosized particles. The aim is to develop a procedure which yields tailored values of sheltering-exposure coef-

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ficients for the different size fractions, correction factors which permit the use of the RTF to compute fraction transports over a mixed bed. There are strong interactions among the various size fractions; for instance, minor admixture of a coarse-end ingredient disproportionately reduces the overall mobility of a finer-grained bed. However, coarse fractions are more mobile in a bed of mixed sizes than they are in a bed of the same uniform size. Dept. of Oceanogr., Old Dominion Univ., Norfolk, VA 23529, USA. 90:2072 Lynch, J.C. ctal., 1989. Recent accretion in mangrove ecosystems based on IsTCs and 2t~ Estuaries, 12(4):284-299. Accretion rates were measured in fringe and basin mangrove forests in river and tidally dominated sites in Terminos Lagoon, Mexico, and a basin mangrove forest in Rookery Bay, Florida. Accretion rates for the Rookery Bay cores ranged from 1.4 to 1.7 mm yr-I; rates at the Mexico sites ranged 1.0 to 4.4 mm yr-I, with an average of 2.4 mm yr-I (determinations here wcre greatly affected by the consolidation corrections, which decreased the apparent accretion rate by over 50% in one case). Accretion rates in fringe sites are generally greater than basin sites, indicating greater subsidence rates in these sediments over longer time intervals. Dept. of Biol., Univ. of Southwestern Louisiana, Lafayette, LA 70504, USA. 90:2073 Mehta, A.J., 1989. On estuarine cohesive sediment suspension behavior. J. geophys. Res, 94(C10): 14,303-14,314. Cohesive sediment suspension response to forcing by currents and waves is examined by defining a physical framework in terms of the vertical distribution of the sediment concentration. This description makes it convenient to identify vertical sediment mass transport 'processes that govern the dynamics of the suspension profile. Simple physical principles have been used to examine suspension profile evolution under a variety of situations and to assess the strengths and limitations of the state-of-the-art understanding in estuarine cohesive sediment transport. Coastal and Oceanogr. Engng Dept., Univ. of Florida, Gainesville, FL 32611, USA. 90:2074 Nichols, M.M., 1989. Sediment accumulation rates and relative scadevel rise in lagoons. Mar. Geol, 88(3-4):201-219. The 22 United States lagoons reviewed exhibit a

OLR(1990)37(4)

range of accretionary differences varying between two end members: (1) a 'surplus" lagoon in which accretion exceeds the relative sea-level rise rate, e.g., by 4.0 mm/yr for short-term (decades) differences in Atchafalaya Bay, and (2) a 'deficit' lagoon in which relative sea-level rise exceeds the accretion rate, e.g., by -4.3 mm/yr for short-term differences in Matagorda Bay. The majority of lagoons have a near balance in which the rate of accretion nearly equals relative sea-level rise. The accretionary status reveals a lagoon continuum that emphasizes the way in which lagoons may be examined in a conceptual model as resultants of accretion and submergence. Short-term accretionary differences reflect the direction of long-term (millennia) differences. Marked accretionary differences, as in Galveston Bay and Mobile Bay, indicate human intervention in the long-term trends. VIMS, School of Mar. Sci., Coll. of William and Mary, Gloucester Point, VA 23062, USA. 90:2075 Oertel, G.F. et al., 1989. Anatomy of a barrier platform: outer barrier lagoon, southern Delmarva Peningul~ Virginia. Mar. Geol, 88(34):303-318. A 7-9 m thick prism of fine-grained sediment occurs below the floor of barrier lagoons of the southern Delmarva Peninsula and provides a platform for retreating barriers to migrate across. Marine microfauna confirm that deposition of mud occurred in a coastal/estuarine environment. However, x-ray radiographic and palynological analyses suggest shallow-water deposition associated with a cool-climate boreal forest. Much of the lagoonal mud behind the barriers is apparently pre-Holocene, and primordial Holocene lagoons were apparently very shallow. Hence, along the southern Delmarva Peninsula, landward-migrating barrier islands retreated across topographic highs composed of silt and clay. Barrier Island Prog., Dept. of Oceanogr., Old Dominion Univ., Norfolk, VA 23529, USA. 90:2076 Perillo, G.M.E. and J.W. Lavelle et al., 1989. Special section: Sediment transport processes in estuaries. [Selected papers from the AGU Chapman Conference, Bahia Blanca, Argentina, 13-17 June 1988.] J. geophys. Rds, 94(C10):14,28714,444; 13 papers. This collection of papers from the symposium represents the diversity of session topics--estuarine bedforms, instrumentation and data analysis, practical applications, cohesive sediment problems, mathematical modes, effects of inhomogeneities, and future research goals and opportunities. Four review

OLR(1990)37 (4)

D. SubmarineGeologyand Geophysics

articles treat estuafine research, cohesive sediment suspension behavior, bedload transport of sand mixtures, and effects of suspended sediment stratification on bottom exchange processes; a fifth paper summarizes future research requirements for the study of processes in estuaries; the remaining papers cover research on remote sensing of sediment transport, laboratory and field studies of fine particle erosion and transport, estuarine bedforms, and modelling of transport processes. (hbf) 90:2077 Perillo, G.M.E. and M.E. Sequeira, 1989. Geomorpboiogic and s&liment transport characteristics of the middle reach of the Bahia Blanca Estuary (Argentina). J. geophys. Res, 94(C10):14,35114,362. Inst. Argentino de Oceanogr., Av. Alem 53, 8000 Bahia Blanca, Argentina. 90:2078

Pilkey, On'in et al., 1989. The sedimentology of three Tunisian lagoons. Mar. Geol, 88(3-4):285-301. Dept. of Geol., Duke Univ., Durham, NC 27706, USA. 90:2079

Reed, D.J., 1989. Patterns of sediment deposition in subsiding coastal salt marshes, Terrebonne Bay, Louisiana: the role of winter storms. Estuaries, 12(4):222-227. Louisiana Univ. Mar. Consortium, Chauvin, LA 70344, USA. 90:2080

Sheng, Y.P. and Catherine Villaret, 1989. Modeling the effect of suspended sediment stratification on bottom exehanooe processes. J. geophys. Res~ 94(C 10): 14,429-14,444. A vertical gradient of suspended sediment concentration often exists in estuaries, particularly within the bottom boundary layer where sediment erosion and deposition' take place. Model simulations of laboratory sediment-laden boundary layers indicate that, as sediments are eroded or resuspended from the bottom, a vertical gradient of suspended sediment concentration can lead to a significant reduction of turbulent shear stresses and slow down the erosion-resuspension process. Hence significant error may be contained in empirical sediment erosion rate formulae derived by ignoring flowsediment interactions. Simulations of a wave boundary layer and a thermally stratified boundary layer are also presented. There is good agreement between measured and simulated mean and turbulent quantities in both cases. Coastal and Oceanogr. Engng Dept., Univ. of Florida, Gainesville, FL 32611, USA.

321 90:2081

Stanley, D.J., 1989. Sediment transport on the coast and shelf between the Nile Delta and Israeli margin as determined by heavy minerals. J. coast. Res, 5(4):813-828. Mediterranean Basin Prog., Natl. Mus. of Nat. History, Washington, DC 20560, USA. 90:2082

Stoddart, D.R., D J . Reed and J.R. French, 1989. Understanding salt-marsh accretion, Scolt Head Island, Norfolk, England. Estuaries, 12(4):228236. Measurements of surface sediment accretion have been obtained for Hut Marsh, using sand marker horizons. More than eighty marker sites were deployed in October 1983, and vertical accretion measured at them in April and October 1986 and April 1987. Data collected by Steers between 1935 and 1957 on the same marsh show a clear relationship between marsh elevation and sedimentation. Current data, together with the results of tidal flow monitoring in creeks on Hut Marsh, show the importance of spatial and temporal patterns of sediment delivery and variations in depositional processes in determining the distribution of sedimentation across the marsh surface. Dept. of Geogr., Univ. of California, Berkeley, CA 94720, USA. 90:2083

Walton, T.L. Jr. and R.O. Bruno, 1989. Longshore transport at a detached breakwater, Phase II. J. coast. Res, 5(4):679-691. Wave heights, periods, directions, and longshore currents were measured by visual observation and the average longshore sediment transport rates were determined from sequential volumetric surveys behind an offshore breakwater which was regarded as a total trap. The data analyzed cover a period of seventeen months; during this period there were twelve surveys of the sediment volume trapped behind the breakwater. The correlation constant is tested and compared with earlier longshore sediment transport results. Coastal Engng Res. Ctr., U.S. Army Eng. Waterways Exp. Sta., P.O. Box 631, Vicksburg, MS 39180, USA. 90:2084

Wells, J.T. and S.-Y. Kim, 1989. Sedimentation in the Albemade-PAmlico lagoonal system: synthesis and hypotheses. Mar. Geol, 88(3-4):263-284. A synthesis of 30 years of published data and new information is presented on the Albemarle-Pamlico system, which includes barrier islands, a deep central basin, four rivers, and extensive fringing embay-

322

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meats. Surficial cover ranges from medium sand in inlets and shoals to fine silts and organic-rich clays in the basin and embayed river mouths and channels. Parts of the system have high sedimentation rates relative to sediment input and rapid vertical flux by large aggregates explains the presence of fluid mud deposits. Fine-grain sediments that escape the estuarine sediment trap eventually come to rest in the deep basin. Short-term advective processes are secondary to sea-level rise and barrier island migration in the net advection of sediments, and at present rates, the system will never reach a sediment-filled state. Inst. of Mar. Sci., Univ. of North Carolina, Morehead City, NC 28557, USA. 90:20ss Wood, M.E., J.T. Kelley and D.F. Belknap, 1989. Patterns of sediment accumulation in the tidal marshes of Maine. Estuaries, 12(4):237-246.

Marshes with four different morphologies (backbarrier, fluvial, bluff-toe, and transitional) showed distinctly different sediment accumulation rates. In general, back-barrier marshes had the highest accumulation rates and bluff-toe marshes the lowest. No causal relationship between modern marsh sediment accumulation rate and relative sea-level rise rate (from tide gauge records) was observed. Marsh accretionary balance (sediment accumulation rate minus relative sea-level rise rate) did not correlate with mean tidal range for this meso- to macro-tidal area. Ice transport of sediment may make a significant contribution to surficial sedimentation on Maine salt marshes. Dept. of Geol. Sci., Univ. of Maine, Orono, ME 04469, USA. 90:2086

Woodroffe, C.D. et al., 1989. Depositional model of a macrotidal estuary and floodplain, South Alligator River, northern Australia_ Sedimentology, 36(5): 737-756. Dept. of Geogr., Univ. of Wollongong, NSW 2500, Australia. 90:2087

Wright, L.D., 1989. Dispersal and deposition of river sediments in coastal seas: models from Asia and the tropics. Neth. J. Sea Res, 23(4):493-500. Diverse mechanisms by which river-borne sediments are dispersed into coastal oceans and the associated deposition patterns are considered for rivers in China and Papua New Guinea. These models contrast sharply with 'conventional' models such as that of the Mississippi. Extremely high suspended sediment concentration off the Huanghe mouth causes sinking, gravity-driven plumes producing rapid deposition very near the mouth and rapid seaward growth of the subaqueous delta. Suspended

OLR (1990) 37 (4)

sediments transported via buoyant plumes from the Purari mouth are trapped inshore by the trades and have their ultimate sink in tidal estuaries. The Jaba, a small fiver with steep gradient and high bed load, has constructed a protruding and rapidly evolving delta. VIMS, School of Mar. Sci., Coll. of William and Mary, Gloucester Point, VA 23062, USA. 90:2088

Yang, C.-S., 1989. Active, moribund and buried tidal sand ridges in the East China Sea and the southern Yellow Sea. Mar. Geol, 88(1-2):97-116. Shallow seismic profiles and borehole data reveal active, inactive, and buried tidal sand ridges in the East China and southern Yellow seas. The ridges consist of clean, well-sorted sands with fairly uniform sequences. The formation, build-up, preservation, and stratigraphic record of the ridges are described and discussed. The observed features have important implications for subsurface recognition of fossil tidal sand ridges, the reconstruction of regional paleogcography and transgressional history, and prediction of potential reservoir sandstones. Intergeos B.V., Statenhof, Reaal 5, 2353 TK Leiderdorp, Netherlands.

D80. Reefs and atolls 90:2089

Harris, P.T. and P.J. Davies, 1989. Submerged reefs and terraces on the shelf edge of the Great Barrier Reef, Australia: morphology, occurrence and implications for reef evolution. Coral Reefs, 8(2):87-98. Echo profiling, side-scan sonar and uniboom reflection profiling, combined with submersible observations for seven locations on the shelf edge and upper slope off the Great Barrier Reef, provide new data on the morphology and extent of submerged reefs and terraces. Finds include an extensive platform at depths rising above the 50 m isobath, and stretching > 2 0 km parallel to the shelf edge, which is backed by a relict lagoon at average depth of 75 m, and numerous features concentrated at depths of 44-46, 6066, 72-78, 80-84, 102-106, and 146-148 m. Ocean Sci. Inst., Univ. of Sydney, NSW 2006, Australia. (hbf) 90:2090

Walbran, P.D. et al., 1989. Crown-of-thorns starfish outbreaks on the Great Barrier Reef: a geological perspective based upon the sediment record. Coral Reefs, 8(2):67-78. Dating of Acanthasterplanci skeletal elements found

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D. Submarine Geology and Geophysics

in the sediments of two reefs where outbreaks of the starfish have occurred over the past 30 years (John Brewer and Green Island reefs, GBR) suggests that A. planci outbreaks may have been occurring for thousands of years on these reefs. Although physical disturbance and bioturbation make identification of individual events impossible, the data indicate that outbreaks have occurred for >_7000 yr on John Brewer Reef and for N3000 yr on Green Island Reef. Geol. Dept., James Cook Univ. of North Queensland, Townsville, Qld. 4811, Australia. (gsb)

D l l 0 . Erosion 90:2091 Aarseth, Inge, Oivind Lonne and Olav Giskeodegaard, 1989. Submarine slides in glaciomarine sediments in some western Norwegian fjords. Mar. Geol~ 88(1-2):1-21. Dept. of Geol., Section B, Univ. of Bergen, Allegt 41, N-5007 Bergen, Norway. 90:2092 Kuijper, Cees, J.M. Comelisse and J.C. Winterwerp, 1989. Research on erosive properties of cohesive sediments. J. geophys. Res, 94(C10):14,34114,350. Experiments on the erosion of soft mud layers in a steady flow were performed in the Delft Tidal Flume and in an annular flume. The results were analyzed using the erosion rate function as derived by Parchure and Mehta. It is concluded that a reasonable description is possible. However, the floe erosion rate appeared to be a function of the bed shear stress. In one ease the erosion rate function needed to be adjusted slightly in order to obtain agreement between measured and calculated suspension concentrations. Delft Hydraulics, Rotterdamseweg 185[, 2629 HD Delft, Netherlands.

D120. Sedimentary processes (deposition, diagenesis, etc.) 90:2093 Castanier, Sabine, Andr6 Maurin and J.-P. Perthuisot, 1989. Experimental bacterial production of spheroidal, fibro-radial carbonate bodies. Discussions about the definition land formation] of oolds. Bull. Soc. gdo/. Ft, (8)5(3):589-595. (In French, English" abstract.) Lab. Biogeol. et

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Biostratigr., Univ. Nantes, 2 Rue de la Houssiniere, 44072 Nantes cedex 03, France. 90:2094 Gaillard, J.-F., Hrl/:ne Pauwels and Gil Michard, 1989. Chemical diagenesis in coastal marine sediments [Villefranche Bay, Mediterranean France]. Oceano/ogica Acta, 12(3): 175-187. We investigated the carbonate system in the pore fluids. Special care was taken in determining pH for computing chemical equilibria on the ionic medium scale and on the infinite dilution scale using the specific interaction approach. Calcite and aragonite are saturated through the entire length of the core. A stoichiometric model of organic matter oxidation coupled with sulphate reduction and precipitation of authigenic minerals is proposed in explanation of the observed distribution of elements. This model suggests that, during the first steps of early diagenesis in these sediments, CaCO 3 and FeS are precipitating from the pore waters. Dept. de Chimie Min. Analyt. et Appliquee, Univ. de Geneve, 30 quai E.-Ansermet, 1211, Geneva 4, Switzerland. 90:2095 Hesse, Reinhard, 1989. Silica diagenesis: origin of inorganic and replacement cherts. Earth-Sci. Rev~ 26(4):253-284. Silicification of non-siliceous sediments affects a variety of rock types and in volcanic edifices is related to hydrothermal activity. Partial and minor ehertification occurs mostly in Phanerozoie carbonates, carbonate-bearing sandstones, evaporites, and fossil wood, and may take place any time during diagenesis or anchlmetamorphism; the silica source is predominantly biogenic. Pervasive to complete silicification has been described in lacustrine, pedogenie, and hydrothermal-volcanogenie rocks and occurs on the scale of single beds, members, or entire formations; the silica source is predominantly inorganic. Chert formation includes direct chemical silica precipitation from solution through a gel stage. Silcretes originate from weathering and soil formation. Dept. of Geol. Sci., McGiU Univ., 3450 Univ. St., Montreal, H3A 2A7, PQ, Canada. 90:2096 Jakobsen, Rasmus and Dieke Postma, 1989. Formarion and solid solution behavior of Ca-rim. doehrosites in marine muds of the Baltic deeps. Geochim. cosmochim. Acta, 53(10):2639-2648. Geol. Survey of Denmark, Dept. of Hydrogeol., Thoravej 8 DK-2400 Copenhagen, Denmark.

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D130. Sediments (rocks, formations, type, composition, etc.) 90:2097

Barrie, J.V. and B.D. Bornhold, 1989. Sudiclal geology of Hecate Strait, British Columbia continental shelf. Can. J. Earth Sci, 26(6):12411254. C-CORE and Dept. of Earth Sci., Memorial Univ. of Newfoundland, St. John's, NF AIB 3X5, Canada. 90:2098

Bornhold, B.D. and D.B. Prior, 1989. Sediment blocks on the sea floor in British Columbia fjords. Geo-Marine Letts, 9(3):135-144. In the deepest parts of Bute and Knight Inlets, British Columbia, unusual blocky mounds of sediment rise abruptly from the otherwise smooth sea floor. The mounds (up to 28 m high, 80 m wide, and 150 m long) display bioturbated surfaces with transverse fractures and elongate depressions. The origin of the mounds and sediment blocks, which contrast with the otherwise flat-lying fjord-bottom strata, remains unknown. Two mechanisms for their formation are considered: (1) subsidence associated with carthquake-induced liquefaction; and (2) uplift driven by the growth of localized gas hydrates in the near-surface sediments. Geol. Survey of Canada, Pacific Geosci. Ctr., Sidney, BC V8L 4B2, Canada. 90:2099

Chamley, Herv~, 1989. Geodynamic control on Messinlan day sedimentation in the central Mediterranean Sea. Geo-Marine Letts, 9(3):179184. Study of clay sedimentation in the Tyrrhenian area during Late Miocene time allows the distinguishing of continental, synsedimentary, and diagenetic influences on the composition of sedimentary rocks, according to geographic location. In south Sicily smectite-rich assemblages were mainly eroded from soils developed under subarid conditions. On the eastern margin of Sardinia abundant micaillite was supplied from exposed areas tectonically rejuvenated during the opening of the Tyrrhenian Sea. In the westernmost part of the Tyrrhenian Basin evaporative environments combined with a strong geothermal gradient allowed the formation of sediments rich in euhedral chlorite. Geol. des Bassins Sediment., Univ. P. et M. Curie, 75752 Paris, Cedex 05, France.

OLR(1990)37 (4)

10):267-273. Although there are relatively few published data on the infrared spectra of biogenic silica, infrared quantitative analysis should prove a promising method for determining the structure of biogenic silica and its presence in sediment. An Si-O bond length of 1.62 A and Si-O--Si angle of 142o6 , are inferred for molecules of marine siliceous skeletons and silica polymorphs~ A model consisting of short chains of SiO4 tetrahedra bounded with apical hydroxyls is proposed, and the processes of silica skeleton sedimentation and diagenesis are discussed. Lab. de Geol. du Museum, 43 rue Buffon, 75005 Paris, France. 90:2101

Frohlich, Franfois and Emmanuelle Wicquart, 1989. Upper Cretaceous and Paleogene sediments from the northern Kerguelen Plateau. Geo-Marine Letts, 9(3): 127-133. Upper Cretaceous and Paleogene pelagic sediments sampled from the northern Kerguelen Plateau are described and correlated with the Late Paleogene sequence drilled at site ODP 737. Taking into account geophysical data obtained by cruise MD26, a Lower Cretaceous age is computed for the unsampled acoustic basement. A major tectonic/volcanic event in the Late Paleogene, related to rifting, gave rise to a marked unconformity and hiatus termed the 'acoustic discordance.' Tertiary sediment facies changes were strongly influenced by the evolution of the Antarctic environment. Lab. de Geol., Mus. Natl. d'Hist. Nat., 43 rue Buffon, 75005 Paris, France. 90:2102

Grrlich, K. et al., 1989. S:Fe M/~sbauer study of a sediment co|nmn in the Gdansk Basin, Baltic Sea: palaeoenvironmental application. Mar. Geol, 88(1-2):49-69. The sediment column of the core examined represents 10,000 yr of prodelta deposition and records a changing environment over that period in the Baltic Sea. Iron minerals were identified in the < 2 /~m fraction of Late Pleistocene-Recent muds using 57Fe MOssbauer spectroscopy, chemical analyses, and x-ray powder diffraction. The salinity and water stratification history of the Baltic during the Late Pleistocene to Recent is inferred using the ironmineral record. Inst. of Geol. Sci., Polish Acad. of Sci., ui. Senacka 3, 31-002 Krakow, Poland.

90:2100

Frrhlich, Francsois, 1989. Deep-sea biogenie silica: new structural and analytical data from infrared Rnalys~ ~--~ological implications. Terra Nova,

90:2103

Gunatilaka, A., 1989. Low-latitude anhydrite from the Red Sea coast: palaeoclimatic and palaeo-

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D. SubmarineGeologyand Geophysics

hydrological implications. Terra Nova, 1(3):280283. In contrast to the Mesozoic and Paleozoic, there are relatively few areas of the globe today which foster anhydrite (CaSO4) formation. Field work in the supratidal Red Sea coast sabkhas of the Sudan has revealed the presence of significant amounts of anhydrite south of 18~ within the rain shadow of the Red Sea Hills, where rainfall averages <80 mm yr-L Data on ancient Arabian and North American anhydrite deposits imply deposition near the Equator and suggest that anhydrite deposits can form at lower latitudes ff rainfall is low and evaporation rates are high. Dept. of Geol., Kuwait Univ., Box 5969, Kuwait 13060, Kuwait. (hb 0

90:2104 Holler, Peter, 1989. Mass physical properties of sediments from Bransfield Strait and northern Weddell Sea. Mar. Geotechnol, 8(1): 1-18. Geol.Palaontol. Inst. und Mus. der Univ. Kiel, Olshausen str. 40-60, D-2300 Kiel, FRG. 90:2105 Jedwab, Jacques, G6rard Blanc and Jacques Boulegue, 1989. Vanadiferous minerals from the Nereus Deep, Red Sea. Terra Nova, 1(2): 188-194. During a chemical survey of the Red Sea, samples were recovered from the Nereus Deep which contained vanadium concentrations >1% V203, but little or no titanium. Optical microscopy revealed that much of the V was bound to the mineral magnetite. A detailed mineralogical and chemical study suggests that the vanado-magnetite is the product of differential hydrothermal leaching of Fe-Ti-oxides present in basic eruptive rock clasts. Lab. de Geochim., CP 160, Univ. Libre de Bruxelles, 50 Av. Roosevelt, B-1050 Brussels, Belgium. (hbf)

90:2106 Kenter, J.A.M. ~ and Wolfgang Schlager, 1989. A comparison of shear strength in calcareous and siliclclastic marine sediments. Mar. Geol, 88(12):145-152. Over 2000 measurements of shear strength versus depth in fine-grained marine sediments, from the literature and our own experiments, were used to study the relationship between carbonate content and strength behavior. Depositional environments include slope, rise and abyssal plain, with depth range to 6 m subbottom depth. Shear strength in siliciclastic sediments shows low variability and increases gradually with depth, but shear strength in the calcareous population is highly variable and increases rapidly with depth. This difference has

325

implications for the stability of submarine slopes. Carbonate sediments build steeper and more variable slopes than siliciclastic sediments, due in part to the higher internal strength of carbonate sediments. Inst. voor Aardwetenschappen, Vrije Univ., De Boelelaan 1085, 1081 HV Amsterdam, Netherlands. 90:2107 Li, Tinghuan and Bo Jin, 1989. Seismic facies analysis of the seafloor instabilities in the Pearl River mouth region. Mar. Geotechnol., 8(1): 19-3 I. High-resolution seismic reflection data acquired in the Pearl River mouth region show shallow faults, buried channels, gas-charged sediments, mud diapirs and sand waves. This paper focuses on the interpretation of their depositional environments, and models a study of the dynamic characteristics of seismic facies parameters, and determination of the velocity-density properties of the geological units, depths, and stratification continuity. Causes of the instabilities are discussed with examples of sea-level change since Quaternary, neotectonic movements, and oceanographic=hydrodynamic processes. The high-resolution seismic prospecting technique is a valuable means of discerning and studying subbottom geohazards, and evaluating engineering/geological conditions. 9 by Taylor and Francis. The Second Mar. Geol. Invest. Brigade, Ministry of Geol. and Min. Resour., Guangzhou, People's Republic of China.

90:2108 Mackin, J.E. and K.T. Swider, 1989. Organic matter decomposition pathways and oxygen consumption in coastal marine sediments. J. mar. Res~ 47(3): 681-716. The possible use of Y.CO2 production, determined from anoxic incubation, and natural solute (O,, NH4 +, SO4-) distributions to infer organic matter decomposition pathways is investigated. Integrated Y.CO2 production from anoxic incubation experiments agreed well with direct measurements of YCO2 fluxes across oxic sediment-water interfaces in Long Island Sound and Flax Pond salt marsh. Anoxic Y-CO2 production, as a function of depth, was used to derive the relative roles of different electron acceptors in the organic matter decomposition process. The results bring into question the generality of assertions that 02 accounts for 50% or more of total organic matter decomposition in reactive nearshore marine sediments. Mar. Sci. Res. Ctr., SUNY, Stony Brook, NY 11794-5000, USA.

90:2109 Mienert, J. and J. Bloemendal, 1989. A comparison of acoustic and rock-magnetic properties of equa-

326

D. SubmarineGeologyand Geophysics torial Atlantic deep-sea sediments: paleoceanographic implications. Earth planet. Sci. Letts, 94(3-4):29 i-300.

P-wave velocities and magnetic susceptibilities were measured on gravity and piston cores and ODP Leg I08 cores from the equatorial Atlantic to test whether climatically driven changes in terrigenous and biogenie fluxes and carbonate dissolution control interrelationships between the two signals. In Pleistocene sediments above the CCD changes in P-wave velocity and magnetic susceptibility are inversely correlated and coherent to changes in glacial-interglacial climate. Below the CCD consistently low P-wave velocities and higher magnetic susceptibilities prevail. Preliminary results demonstrate that combined measurements of acoustic and magnetic signals provide a tool for characterizing glacial-interglacial pelagic sedimentation, pelagic sedimentation above the CCD, increases in carbonate dissolution, and areas below the CCD. GEOMAR, Forschungszentrum fur Mar. Geowiss. an der Christian Albrechts Univ., D-2300 Kiel 14, FRG.

OLR (1990)37 (4)

The spill-over forms a sandy sedimentary deposit that acts as a topographic obstruction to the turbidity current flow from the south. This obstruction is expressed by the westward migration of a NW--SE oriented turbidity-current-cut channel. USGS, Woods Hole, MA 02543, USA. 90:2114

Shor, A.N. and D.J.W. Piper, 1989. A large Late Pleistocene blocky debris flow on the central Scotlan Slope. Geo-Marine Lefts, 9(3):153-160. A SeaMARC I side-scan sonar survey on the central Scotian Slope shows a blocky debris flow with high surface roughness between the 1000 and 2000 m isobaths, covering an area of ~1000 km 2. The flow is at least 20 m thick, occurring as lenses within channels and as sheets on intervalley areas. The surface reflectivity is variable, with blocks and depressions 50 to 200 m wide and relief of 5 to 20 m. The source zone lies within two canyons on the upper slope and has relatively smooth surface reflectivity, in contrast to the gullied slope to either side. Hawaii Inst. of Geophys., Univ. of Hawaii at Manoa, 2525 Correa Rd., Honolulu, HI 96822, USA.

90:2110

Murty, P.S.N. and K.S.R. Rao, 1989. Clay mineralogy of Visakhapatnam shelf sediments, east coast of India. Mar. Geol~ 88(1-2): 153-165. Geol. Survey of India, East Coast Div.-II, 90 KirIampudi Layout, Visakhapatnam 530 023, India.

D140. Submarine hydrology (springs, hydrothermal deposits, etc.) 90:2115

90:2111

Nemoto, Kenji et al., 1989. Echo character of the Uebiura Bay, Shizuoka, and its relation to

sedimentary structure and processes. J. Fac. mar. Sci. Technol~ Tokai Univ, 28:95-118. (In Japanese, English abstract.) 90:2112

Rao, P.S., 1989. Sonograph patterns of the central western continental shelf of India. J. coast. Res, 5(4):725-756. Natl. Inst. of Oceanogr., Dona Paula, Goa 403 004, India. 90:2113

Schwab, W.C. et al., 1989. Sea-floor observations in the Tongue of the Ocean, Bahamas: an Axgo/SeaMARC survey, Geo-Marine Letts, 9(3): 171-178. SeaMARC side-scan sonographs and Argo video and photographic data suggest that the recent sedimentary environment of the floor of the Tongue of the Ocean is controlled by an interplay of turbidity current flow from the south, sediment spill-over from the carbonate platform to the east, and rock falls from the west carbonate escarpment.

Massoth, G.J. et al., 1989. Submarine venting of phase-separated hydrothermal fluids at Axial Volcano, Juan de Fuca Ridge. Nature, Lond~ 340(6236):702-705. It has been expected, because of the physical properties of seawater at pressures and temperatures encountered during hydrothermal circulation, that phase-separated fluids would discharge from ridgecrest vents. Although this notion is supported by the reported large deviations in chlorinity of vent fluid relative to that of seawater, by venting at P - T conditions clearly within the two-phase region, and by fluid-inclusion data, unequivocal identification of phase-separated venting fluids remains elusive. Here we report observations of chloride- and metaldepleted, gas-enriched fluids from a shallow vent field on the Juan de Fuca Ridge which confirm the expectation that phase-separated effluents are delivered to the deep ocean from some seafloor venting systems. PMEL, NOAA, 7600 Sand Point Way, N.E., Seattle, WA 98115-0070, USA. 90:2116

Rona, P.A. and K.G. Speer, 1989. An Atlantic hydrotherma! plume: Trans-Atlantic Geotraverse

OLR (1990) 37 (4)

D. Submarine Geology and Geophysics

(TAG) area, Mid-Atlantic Ridge crest near 26~

J. geophys. Res, 94(BI0): 13,879-13,893. The physical characteristics of an Atlantic hydrothermal plume and its seafloor sources are described from the first data set of water column properties associated with a high-temperature source area at a slow-spreading oceanic ridge, the Trans-Atlantic Geotraverse Hydi'othermal Field in the rift valley of the Mid-Atlantic Ridge at 26~ 44~ The source area is a mound, up to 250 m wide and 50 m high, constructed primarily of massive sulfides between depths of 3620 and 3670 m at the base of the east wall. The hydrothermal plume and mound are inferred to have grown in size and complexity in response to development of hydrothermal flow and discharge regimes for at least 104yr. AOML, NOAA, Miami, FL 33149, USA.

90:2117 Uchupi, Elazar and R.D. Ballard, 1989. Evidence of hydrothermal activity on Marsili Seamount, Tyrrhenian Basin. Deep-Sea Res. 36(9A): 1443-1448. Video transects along the crest of Marsili Seamount, Tyrrhenian Basin revealed the presence of an extensive hydrothermal mineral deposit emplaced by a convection current system. Geol. and Geophys. Dept., WHOI, Woods Hole, MA 02543, USA.

327

90:2119 Arslanov, Kh.A., M.S. Barash and V.Yu. Kuznetsov, 1988. Geochronology of the Middle and Upper Pleistocene as indicated by sediments of the North Atlantic. Ocfano/ogy (a translation of Okeanologiia), 28(4):502-507. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. 90:2120 Auzende, J.-M. et al., 1989. Stratigraphy of the scarps bounding the Porcupine Seabight: preliminary results of the Cyapore cruise (July-August 1980. Oceanologica Acta, 12(3):!17-131. (In French, English abstract.) The Franco-British cruise to obtain geological profiles across the Porcupine and Goban margins established that the Porcupine bank margin consists of a metamorphic basement of probable Caledonoid age with evidence of Hercynian imprint, implying that the previously recognized Varisean orogenic limit should be moved northward. The Porcupine margin's highly metamorphic basement is overlain by Paleozoie sediments and an almost tabular Mesozoic cover. The north Goban spur section consists of a Barrenian-Eocene sediment cover lying on weakly metamorphosed Paleozoic basement. The. data suggest a simple 'stair' structure and show that bathyal conditions do not appear before Vracono-Cenomanian times. CNRS, IFREMER, Ctr. de Brest, BP n. 70, 29263 Plouzane, France.

90:2118 Altabet, M.A. and W.B. Curry, 1989. Testing models of past ocean chemistry using Foraminifera ISN/14N. Globalbiogeochem. Cycles, 3(2): 10%119.

90:2121 Bouquillon, Anne, Herv6 Chamley and Franqois FrOhlich, 1989. Late Cenozoic clay sedimentation in the northeastern Indian Ocean. Oceanologica Acta, 12(3):133-147. (In French, English abstract.)

We propose that tSNp4N ratios for the organic matrix of preserved Foraminifera yield an interpretable 815Nrecord. Results of models developed to study the relatirnship between plausible changes in the ocean's N cycle and resulting changes in the ~SN/14N ratio of dissolved NO3- demonstrate that 'SN/J4N ratios exhibit excursions during periods in which the oceans are accumulating or losing N, regardless of the means by which these changes occur. Foraminifera ~SN/~4Nresults for a Pacific and an Atlantic core provide evidence against wide spread glacial anoxia. We suggest that increasing shelf-sediment denitrification upon deglaciation reduced N concentrations in the modern ocean. Ambiguities between the two Foraminifera 'SN/'4N records indicate that local effects associated with changes in hydrography or ecology need further study. WHOI, Woods Hole, MA 02543, USA.

Analysis of some 400 samples from 16)piston cores and one DSDP hole (Leg 22 Site 218) identified five sedimentary provinces and six source areas. Late Cenozoic clay sedimentation depends mainly on a NE Indian Ocean detrital supply. The only significant in-situ formation of marine silicates was of amorphous Si-Fe complexes and smectites. Autochthonous processes affecting pelagic environments are characterized by low sedimentation rates and minimal detrital input, and early diagenetie processes by formation of lathed clays. Quaternary climatic variations contemporary with glacial/interglacial alternations are recorded in the clay successions and Late Cenozoic Himalayan mountain belt phases are reflected in turbidite- and illite-rich sequences. Lab. de dynam, sediment, et struct., Unite assoc, au CNRS n. 719, Univ. de Lille.I, 59655 V/lleneuve-d~ France.

D170. Historical geology, stratigraphy

/

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D. SubmarineGeologyand Geophysics

90:2122 Burdett, J.W., M.A. Arthur and Mark Richardson, 1989. A Neogene seawater sulfur isotope age curve from calcareous pelagic microfossils. Earth planet. Sci. Letts, 94(3-4):189-198.

Until now knowledge of the sulfur isotopic composition of seawater through geologic time has depended on stable isotopic analysis of sulfate from evapodtes. A method is outlined for constructing secular sulfur isotope curves using a carbonateassociated sulfate extraction technique on carbonate tests of planktonic foraminifers. An analysis of Miocene-Recent pelagic marine sediments, supplemented by data for Miocene marine evaporites from the Gulf of Suez, hadicates that the 834S of seawater has decreased ~2.5 ppt over the past 25 m.y., primarily over the past 5 m.y., paralleling a decrease in the 8uC of dissolved oceanic bicarbonate. Grad. School of Oceanogr., Univ. of Rhode Island, Narragansett, RI 02882, USA. 90:2123 Evans, M.W., A.C. Hine and D.F. Belknap, 1989. Quaternary stratigraphy of the Charlotte Harbor estuarine--lagoon system, southwest Florida: implications of the carbonate-silicielasfic transition. Mar. Geol, 88(3-4):319-348. High-resolution seismic profiling, vibracores, and sediment samples were used to interpret the stratigraphy and evolution of Charlotte Harbor, a complex lagoon and estuarine system underlain by Tertiary carbonates and Quaternary siliciclastie sedimentary sequences. The Tertiary carbonates have undergone extensive dissolution and collapse, and Late Neogene deposition has infilled most pre-Quaternary relief. Paleotopography and sediment availability have controlled locations and sedimentary environments. The distribution of three Quaternary sequences and an Early-Middle Pleistocene seismic unconformity indicate that Quaternary sea-level,fluctuations have repeatedly caused coastal systems to migrate t~ough the area leaving records of at least two Pleistocene barrier-lagoon systems. Dept. of Geol., Univ. of Rhode Island, Kingston, RI 02881, USA. 90:2124 Grebennikova, T.A. and S.P. Kletnev, 1988. A new method of determining Pleistocene water temperatures from fossil diatom algae as exemplified by the Sea of Japan. Oceanology (a translation of Okeanologiia), 28(4):471-477.

Investigation of diatom algae in 91 samples of surface sediments of the Sea of Japan indicates that their distribution is related to the mean annual SST.

OLR (1990)37 (4)

Types and subtypes of the subarctic, boreal and subtropical thanatocoenoses, which succeed each other at mean annual temperature intervals of 2-3*, are identified. A comparison of present-day diatom thanatocoenoses with fossil complexes in a core from the Yamato Rise is used to reconstruct temperature variations in this region. Comparison of the results with a curve obtained earlier from this core based on the distribution of planktic Foraminifera indicates good agreement. Pacific Inst. of Geogr., Far Eastern Sci. Ctr., Acad. of Sci., Vladivostok, USSR. 90:2125 Hendry, Malcolm and Gunnar Digerfeldt, 1989. Palaeogcography and pala_~aenvironments of a tropical coastal wetland and offshore shelf during Holocene submergence, Jamaica. Palaeogeogr. PalaeoclimatoL Palaeoecol~ 73(1-2):1-10. Geol. Dept., Univ. of the West Indies, Mona, Kingston 7, Jamaica. 90:2126 Hoang, C.-T. and P.J. Hearty, 1989. A comparison of U-series disequilibrium dates and amino acid epimerization ratios between corals and marine molluscs of Pleistocene age. Chem. Geol, 79(4): 317-323. Ctre. des Faibles Radioact., Domaine du CNRS, F-91198 Gif sur Yvette Cedex, France. 90:2127 Johnson, K.R. et al., 1989. High-resolution leaf-fossil record spanning the Cretaceous/Tertiary boundary. Nature, Lond, 340(6236):708-710.

Megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution, but have previously lacked the sample size and stratigraphie spacing needed to resolve latest Cretaceous floral history. We have now combined megafloral data from a 100m-thick composite K / T boundary section in North Dakota with detailed palynological analysis. Here the boundary is marked by a 30'7o palynofloral extinction coincident with iridium and shockedmineral anomalies that lies 2 m above the highest dinosaur remains. The megaflora undergoes a 79% turnover across the boundary, and smaller changes below it. This pattern is consistent with latest Cretaceous climatic warming preceding a bolide impact. Dept. of Geol. and Geophys., Yale Univ., New Haven, CT 06511, USA. 90:2128 Keigwin, L.D. and E.A. Boyle, 1989. Late Quaternary paleochemistry of high-latitude surface waters. Palaeogeogr. Palaeoclimatol. Palaeoecol,

OLR (1990) 37 (4)

D. Submarine Geology and Geophysics

73(1-2):85-106. Stable isotopic analysis of coretop samples from the Atlantic, Pacific and Southern oceans shows no significant correlation between the 6uC of Neogloboquadrina pachyderma and either 8'3C or PO 4 in seawater. Conversely, Cd/Ca ratios in planktonic Foraminifera are consistent with the surface water PO4 content. The level of maximum glaciation (18,000 yrBP), identified by CLIMAP and 6'80, was chosen for mapping. Isopleths of 6~80 on N. pachyderma in the North Atlantic reveal a pattern largely influenced by SST. From the combined Cd/Ca and 613C data there is no evidence for an upwelling gyre in the eastern North Atlantic during the latest glacial maximum, nor evidence that the southern and northern oceans had significantly different levels of preformed nutrients than today. WHOI, Woods Hole, MA 02543, USA. 90:2129 Lorius, C. et al., 1989. Long-term climatic and environmental records from Antarctic ice. Geophys. Monogr. Am. geophys. Un, 52:11-16. Vostok (East Antarctica) isotope-based temperature and CO 2 records show a large 100-ky signal with changes of the order of 10~ and 70 ppmv respectively. These features suggest a fundamental link between the climate system and the carbon cycle and point out the possible role of CO2, in addition to insolation inputs, in accounting for the observed temperature history. Accumulation (precipitation) values during the coldest stages are ~50% of the current rate. Ice deposited during these coldest stages is also characterized by high concentrations of marine and terrestrial aerosols; peaks likely reflecting higher wind speeds, more extensive arid areas on surrounding continents and greater exposure of continental shelves. There is no indication of a long-term relationship between volcanism and climate. Lab. de Glaciol. et de Geophys. de l'Environ., B.P. 96 3840~ St. Martin d'Heres cedex, France. 90:2130 Mello, M.R. et at., 1989. Late Cretaceous anoxic events in the Brazilian continental margin. Org. Geochem, 14(5):529-542. The organic contents, Roek-Eval pyrolysis results and biological marker distributions of Cenomanian-Maastrichtian pelitic sediments from the Brazilian continental margin, together with taxonomic selection and distribution patterns of microfossil assemblages, indicate that intermittent anoxic events occurred during the Cenomanian--Santonian with deposition taking place in progressively deeper waters. The widely recognized Cenomanian-

329

Turonian and Santonian 'oceanic anoxie events' are evident in the Cassiporr, Cear~i, Sergipe/Alagoas, and Campos basins, as well as in Coniacian beds. In contrast, the Campanian-Maastrichtian was an interval of oxygenated conditions marked by sediments of low organic carbon content and highly diversified, abundant calcareous and agglutinated benthonie Foraminifera. Univ. of Bristol, School of Chem., Cantock's Close, Bristol BS8 ITS, UK. 90:2131 Miller, G.H. et al., 1989. Glacial history and marine environmental change during the lust interglacial-glacial cycle, western Spitsbergen, Svalbard. Boreas, 18(3):273-296. Ctr. for Geoehronol. Res. INSTAAR, Univ. of Colorado, Boulder, CO 80309-0450, USA. 90:2132 Pye, K. and L.-P. Zhou, 1989. Late Pleistocene and Holocene aeolian dust deposition in north China and the northwest Pacific Ocean. Palaeogeogr. PalaeoclimatoL Palaeoeeol, 73(1-2): 11-23. Rates of dust deposition in the North Pacific and the central loess plateau of China show a poor correlation during the last 30,1300 yr, although in both cases the dust was derived from deserts in northern China. These differences reflect the different nature of wind conditions responsible for dust transport to the loess plateau and the North Pacific. Changes in continental aridity have probably played only a minor role in controlling the magnitude of the dust flux to the North Pacific. Postgrad. Res. Inst. for Sedimentol., Univ. of Reading, Whiteknights, Reading RG6 2AB, UK. 90:2133 Ramm, Mogens, 1989. Late Quaternary carbonate sedimentation and paleo-oceanography in the eastern Norwegian Sea. Boreas, 18(3):255-272. Four gravity cores from the eastern Norwegian Sea are studied. Absolute accumulation rates are quantified and variations in carbonate sedimentation and their implications for the paleo-oceanographic history of the Norwegian Sea are described. In the eastern Norwegian Sea, interglacial, ice-free conditions were developed during oxygen-isotope stages 1 and 5e. Slightly elevated summer temperatures in periods during isotope stages 2 and 7 are demonstrated by increased contents of subpolar planktic Foraminifera. Organic-rich sediments and intensive carbonate dissolution in some parts of isotope stages 4 and 6 indicate corrosive bottom waters. Well* preserved foraminiferal assemblages from stage 2 show more oxygenated bottom waters and more effective bottom water renewal in this period than

330

D. SubmarineGeologyand Geophysics

during stage 3. Dept. of Geol., Univ. of Oslo, P.O. Box 1047 Blindern, N-0316 Oslo 3, Norway.

90:2134 Rau, G.H., Taro Takahashi and D.J. Des Marais, 1989. Latitudinal variations in plankton ~t3C: implications for CO, and productivity in past oceans. Nature, Lond~ 341(6242):516-518. High-latitude isotope depletion in plankton develops at CO, partial pressures (pCO, levels) that are often below that of the present atmosphere (340 ttatm), and usually below that of equatorial upwelling systems (>340 ttatm). Nevertheless, because of the much lower water temperatures and, hence, greater CO, solubility at high latitude, the preceding pCO2 measurements translate into Antarctic surface-water CO, concentrations that are up to 2.5-times higher than in equatorial waters. An oceanic pCO2 level of ~800 /tatm (over twice the present atmospheric pCO~) in a warmer low-latitude Cretaceous ocean would have been required to produce the plankton t~C depletion preserved in Cretaceous sediments. Inst. of Mar. Sci., Univ. of California, Santa Cruz, CA 95064, USA.

90:2135 Smith, P.E. and R.M. Farquhar, 1989. Direct dating of Phanerozoic sediments by the 23sU-Z~ method. Nature, Lond, 341(6242):518-521. Dept. of Phys., Univ. of Toronto, ON M5S 1A7, Canada. 90:2136 Thompson, L.G. et al., 1989. Hoiocene-Late Pleistocene climatic ice core records from QinghaiTibetan Plateau. Science, 246(4929):474-477. Three ice cores tp bedrock from the Dunde ice cap of China provide a detailed record of Holocene and Wisconsin-W0rm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative 8tsO ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly ~10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago. 9 by AAAS. Byrd Polar Res. Ctr., Ohio State Univ., Columbus, OH 43210, USA.

OLR(1990)37 (4)

D180. Paleontology (see also E-BIOLOGICAL OCEANOGRAPHY) 90:2137 Boltovskoy, Esteban and Demetrio Boltovskoy, 1989. Paleocene-Pleistocene benthic foraminiferal evidence of major paleoceanngraphlc events in the eastern South Atlantic (DSDP Site 525, Walvis Ridge). Mar. Micropaleont, 14(4):283316. Benthic foraminifers in the size fraction >0.073 were studied in 88 Paleocene-Pleistocene samples. Clustering of samples on the basis of the 86 most abundant foraminifers allowed separating two major assemblage zones--the Paleocene-Eocene and Oligocene-PIeistocene--and each of these were subdivided into three minor subzones. At least one major bottom-water temperature drop is synchronous with a decrease in specific diversity, and a Middle Miocene diversity maximum might be associated with a 8t3C increase at ~16-12 Ma. Highest abundances occurred in the Late Paleocene and Early Pleistocene. Museo Argentino de Cienc. Nat. 'Bernardina Rivadavia', Avda. Angel Gallardo 470, 1405 Buenos Aires, Argentina. 90:2138 Guernet, Claude and Francis Lethiers, 1989. Ostracodes and research of paleoenvironments: a critical review. Bull. Soe. g~ol. Fr, (8)5(3):577588. (In French, English abstract.) Because ostracodes live in almost all aquatic environments, study of their assemblages and morphofunctional analysis allow paleoenvironmental characterization. Some examples (paleosalinities and oxygen content) are given and commented on. Studies of diversity and ontogeny allow estimation of environmental stability and of climate type. Taphonomie observations lead to estimations of sedimentation, paleocurrents, transport, and bioturbation. Lab. Micropaleontol., Univ. Paris 6, 4 pl. Jussieu, 75252 Paris cedex 05, France. 90:2139 Koutsoukos, E.A.M., P.N. Leary and M.B. Hart, 1989. Farasella Michael (1972): e~idence of ecophenotypic adaptation of a planktonic foraminifer to shallow-water carbonate environments during the Mid-Cretaceous. J.foram. Res, 19(4): 324-336. Petrobras-Cenpes, Ilha do Fundao, CEP 21910, Rio de Janeiro, Brazil. 90:2140 Leckie, R.M., 1989. A paleoceanographic model for the early evolutionary history of planktonic Foraminifera. Palaeogeogr. Palaeoelimatol.

OLR(1990)37 (4)

D. SubmarineGeologyand Geophysics

Palaeoecol, 73(1-2): 107-138. The Aptian through lower Cenomanian record of adaptive radiation in planktonic Foraminifera is examined with the focus on diversity trends and morphologic development and the possible paleoceanographie conditions that may have significantly influenced the evolutionary history of Mid-Cretaceous plankton. An important component of this paper is a review of two aspects: plankton ecology and the significance of planktonic foraminiferal diversity, and Mid-Cretaceous paleoceanography. Dept. of Geol. and Geogr., Univ. of Massachusetts, Amherst, MA 01003, USA. 90:2141

Loubere, Paul, 1989. Bioturbation and sedimentation rate control of benthic microfossll taxon abundances in surface sediments: a theoretical approach to the analysis of species microhabitats.

Mar. MicropaleonG 14(4):317-325. A computer model integrating depth stratified taxon production with varying sedimentation and mixing rates indicates significant assemblage variation through the mixed layer results from taxon depth stratification in sediments; infaunal taxon fossil abundances increase nonlinearly in the bioturbated zone down to the level of the taxon habitat; surface sediment assemblages can be strongly affected by sedimentation rate and mixing rate; and sediment abundances of each taxon's shells can be used to determine long-term taxon depth zonation within sediments. Dept. of Geol., Northern Illinois Univ., DeKalb, IL 60115, USA. 90:2142

Malmgren, B.A., 1989. Coiling patterns in terminal Cretaceous planktonic Foraminifera. J. foram. Res, I9(4):311-323. Dept. of Mar. Geol., Univ. of Gothenburg, Box 7064, S-402 32 Gothenburg, Sweden.

331

macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. 9 by AAAS. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK. 90:2144 Nagy, J. and H.O. Johansen, 1989. Preservation and distribution pattern of Reophax metensis (Foraminifera) in the Jurassic of the North Sea. J. foram. Res, 19(4):337-348. Dept. of Geol., Univ. of Oslo, P.O. Box 1047, Blinderu, 0316 Oslo 3, Norway. 90:2145

Premoli Silva, Isabella and Anne Boersma, 1989. Atlantic Paleogene planktonic foraminiferal bioprovincial indices. Mar. Micropaleont, 14(4): 357-371. Morphologies and wall features of Paleogene planktonic Foraminifera are useful for delimiting paleobioprovinces and for the interpretation of Paleogene paleo-oceanography. More specialized morphologies within a lineage or a genus characterize the lower latitudinal range of that group or genus. Therefore, morphologies deviating from the simple globigerine plan signal the lower latitudinal end of a specific or generic range. Larger mean sizes of a species occur at lower latitudes. Significant to paleo-oceanographie reconstructions is the geographic migration of morphologies into upwellings or during climatic cooling; morphotypes with higher latitude characters proliferate in lower latitude assemblages. Dipart. di Sci. della Terra, Univ. di Milano, Via Mangiagalli 34, 20133 Milano, Italy. 90:2146

Morris, S.C., 1989. Burgess Shale faunas and the Cambrian explosion. Science, 246(4928):339-346.

Williams, H.F.L., 1989. Foramlmf"eral zonations on the Fraser River Delta and their application to paleoenvironmentai interpretations. Palaeogeogr. PalaeoclimatoL Palaeoecol, 73(1-2):39-50.

Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic. These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the

Well-defined elevational zonations of foraminiferal species were found over the intertidal surface of the sand-rich Fraser River Delta and were also apparent on the delta foreslope, although data here are more limited. Application of these findings to the interpretation of dcpositional environments within drillcores from the delta provided independent evidence of a 4 to 5 m lower sea-level during the MidHolocene. This finding is in good agreement with a seaMevel curve developed for the Fraser Lowland region. Dept. of Geogr. and Anthropol., Univ. of North Texas, Denton, "IX 76203, USA.

90:2143

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90:2147

Zachariasse, W.J. et al., 1989. Early Late Pliocene biochronology and surface water temperature

variations in the Mediterranean. Mar. Micro-

paleont, 14(4):339-355. A high-resolution magnetobiostratigraphy is presented for the upper reversed Gilbert to the upper normal Gauss subehron in Sicily which provides ages for principal Mediterranean bioevents. Summer and winter SST estimates for 3.50 to 2.92 Ma are based on abundances of Globigerinoides sacculifer and Globorotalia puncticulata with an average resolution of ~5000 yr. Short term variations in SST and in sediment color and carbonate content are primarily controlled by equinoxal precession. Longterm changes include warming at 3.38 Ma, believed to be associated with final closure of the Isthmus of Panama, and cooling at 3.18 Ma, linked to a first stage of Northern Ilemisphere continental ice growth. Inst. of Earth Sci., Univ. of Utrecht, Budapestlaan 4, 3584 CD Utrecht, Netherlands.

D200. Gravity, geodesy, magnetism

OLR (1990) 37 (4)

phys. Res, 94(BI0):14,153-14,166. Long-period ( > I day) behavior of seafloor electromagnetic fields during EMSLAB is considered with emphasis on interpretation of oceanic motions. A summary of the physics of motional electromagnetic induction is included. It is shown that seafloor and terrestrial magnetic variations have similar spectra shapes, indicating a common origin, but the seafloor electric field is not consistent with either at periods > 4 days, thus suggesting an oceanic source; seafloor horizontal electric field data exhibit the broadband coherence characteristic of ionospheric sources only at periods < 1-2 days. The observations demonstrate the power of electromagnetic array methods for the study of long-period oceanic behavior. AT&T Bell Lab., 600 Mountain Ave., Murray Hill, NJ 07974, USA.

90:2151

Chave, A.D. and D.J. Thomson, 1989. Some cornmeats on magnetotelluric response function estimation. J. geophys. Res., 94(B 10): 14,215-14,225. AT&T Bell Lab., 600 Mountain Ave., Murray Ilill, NJ 07974, USA.

90:2148

Arkani-Hamed, J. and J. Verhoef, 1989. Generalized inversion of scalar magnetic anomalies: magnetization of the crust off the east coast of Canada. Geophys. Monogr. Am. geophys. Un, 51:255-270. A generalized inversion technique transforms scalar magnetic anomalies into crustal magnetization while taking into account variations in geomagnetic field directions and the effect of the topography of the upper and lower surfaces of the crustal magnetic layer on the magnetic anomalies. The crustal magnetic susceptibility models show better correlation with geological features than do the observed magnetic anomalies. Basement topography in the oceanic regions has only a minor influence on the magnetic anon~alies, suggesting that the magnetic anomalies are largely due to lateral variations in the magnetization of the crust. Dept. of Geol. Sci., McGill Univ., Montreal, PQ HJA 2A7, Canada. 90:2149

Bahr, Karsten and J.H. Filloux, 1989. Local Sq response functions from EMSLAB data. J. geo-

phys. Res,

94(B10):!4,195-14,200. Inst. fur Meteorol. und Geophysik, Johann Wolf gang Goethe Univ., 6000 Frankfurt am Main, FRG. 90:2150

Chave, A.D. et al., 1989. Observations of mofional electromagnetic fields during EMSLAB. J. geo-

90:2152

Chen, J., II.W. Dosso and W. Nienaber, 1989. Lalmratory electromagnetic model results for the EMSLAB region. J. geophys. Res, 94(B10): 14,167-14,172. The model includes a simulation of the Juan de Fuca Plate subducting the Canadian-U.S. Pacific Northwest region. The subducting plate is taken to be horizontal offshore, dipping at 10 ~ beneath the coast, then inland bending farther to dip at 45 ~ in the Washington-K)regon region and at 30 ~ in the British Columbia region. For inland sites the apparent resistivity for the telluric field component parallel to the coast, and thus also parallel to the strike of the dipping conductive substructure, depends strongly on period, while the resistivity for the telluric field perpendicular to the coast is largely a galvanic effect and changes less with period. The amplitude of the vertical to horizontal magnetic field ratio shows a saddle shaped response, with the coastal maximum followed by a second maximum inland due to the dipping substructure. Further, rather than decreasing rapidly with distance inland as expected for a simple coast effect, the field ratios retain si~ificant values large distances inland for periods of 3-120 rain. Dept. of Phys., Univ. of Victoria, P.O. Box 1700, Victoria, BC v g w 2Y2, Canada.

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D. SubmarineGeologyand Geophysics

90:2153 Egbert, G.D., 1989. Multivariate analysis of geomagnetic array data. 2. Random source models. J. geophys. Res, 94(B10):14,249-14,265. Coll. of Oceanogr., Ocean Admin. Bldg. 104, Oregon State Univ., Corvallis, OR 97330, USA. 90:2154

Egbert, G.D. and J.R. Booker, 1989. Multivariate analysis of geomagnetic array data. 1. The response space. J. geophys. Res, 94(B10): 14,22714,247. Coll. of Oceanogr., Ocean Admin. Bldg. 104, Oregon State Univ., Corvallis, OR 97330, USA. 90:2155

333

28:75-94. (In Japanese, English abstract.) Topographic and geomagnetic surveys of a large flat-topped seamount, or guyot, were carried out as part of a study of the cobalt-rich manganese crust near the Marcus-Necker Islands at the intersection of Hawaiian geomagnetic lineations and Japanese lineations. Its peak rises >3500 m above the adjacent seafloor at depths of 5000--5500 m, and includes such characteristic features as erosional terraces, cliffs, and volcanic cones. The geomagnetic survey shows a declination of 13" and an inclination of -25 ~ indicating that the guyot developed as a normally magnetized seamount near the Equator, then moved to the present location. 90:2158

Filmer, P.E. and M.K. McNutt, 1989. Geoid anomalies over the Canary Islands group. Mar. geophys. Res, 11(2):77-87.

Jiracek, G.R. et al., 1989. Two-dimensional mamaetotelluric inversion of the EMSLAB Lincoln Line. J. geophys. Res~ 94(B10):14,145-14,151.

The Canary Islands geoid anomaly shows only a short-wavelength high associated with island topography. The predicted anomaly best matches the observed geoid when we assume that the lithosphere is a very stiff plate. We find no evidence for shallow reheating or a mantle plume, since there is no evidence of a midplate swell and the corresponding elastic thickness is appropriate for the age of the seafloor on which the island group rests. Dept. of Earth, Atmos., and Planet. Sci., MIT, Cambridge, MA 02139, USA.

Two-dimensional Backus-Gilbert inversion of EMSLAB land magnetotellurie data along the 200-kin-long Lincoln Line reveals three centralized conductive zones at depths of 20--40 kin; a slightly conducting zone at 30-35 km depth under the Oregon Coast Range, which may be the top of the subducting plate; a prominent conduction zone at 30-35 km depth under the Western Cascades (too shallow to be the subducting plate); and a highly conducting lower crust east of the High Cascades. Two vertical conductive regions are also revealed: one under the Willamette Valley, where an Eocene trench may have left a suture zone; another coincident with surface hydrothermal activity along the Western-High Cascades boundary. It is believed that hot, saline water is the major source of the conductive occurrences. Dept. of Geol. Sei., San Diego State Univ., San Diego, CA 92182, USA.

90:2156

Gough, D.I. et al., 1989. Conductive structures and tectonics beneath the EMSLAB land array. J. geophys. Res, 94(B10): 14,099-14,110. The principal aim of the electromagnetic sounding experiment EMSLAB (ElectroMagnetic Sounding of the Lithosphere and Asthenosphere Beneath) is the study of structure, in terms of electrical conductivity, of the lithosphere and asthenosphere beneath the Juan de Fuca of.eanic plate and its subduetion under the North American continent. In this paper we discuss anomalies in long-period magnetovariation fields recorded by the large array of land-based magnetometers. In particular, we relate the conductive structures revealed by this array to the active tectonics of the region. We intend later to model structures beneath the continental edge and ocean making use of data from both land and seafloor stations. Dept. of Phys., Univ. of Alberta, Edmonton, AB T6G 2.J1, Canada. 90:2157

Ishikawa, Hidehiro et al., 1989. Topography and magnetic structure of a seamount south of Marcus Island. J. Fac. mar. Sci. Technol, Tokai Univ,

90:2159

Jones, A.G. et al., 1989. A comparison of techniques for magnetoteHurie response function estimation. J. geophys. Res, 94(B10):14,201-14,213. Geol. Survey of Canad.a, 1 Observatory Crescent, Ottawa, ON K I A 0Y3, Canada. 90:2160

Kodama, Kazuto, 1989. Paleomngnetic study of the upper Cretaceous Izumi strike--~lip basin along the median tectonic line in southwest Japan. Geophys. Monogr. Am. geophys. Un~ 50:239-248. Dept of Geol., Kochi Univ., Kochi 780, Japan. 90:2161

Livelybrooks, D.W. et al., 1989. A magnetoteiluric study of the High Cascades graben in central Oregon. J. geophys. Res~ 94(B10):14,173-14,184.

334

D. SubmarineGeologyand Geophysics Dept. of Geol Sci., Univ. of Oregon, Eugene, OR 97403, USA.

90:2162 Mitrovica, J.X. and W.R. Peltier, 1989. Pleistocene deglaclation and the global gravity field. J. geophys. Res~ 94(B10):13,651-13,671. Dept. of Phys., Univ. of Toronto, ON MSS IAT, Canada. 90:2163 Murthy, I.V.R. and S.J. Rao, 1989. A FORTRAN 77 program for inverting gravity anomalies of twodimensional basement structures. Computers, Geosciences, 15(7): 1149-1156. Dept. of Geophys., Andhra Univ., Visaldaapatnam 530 003, A.P., India.

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90:2166 Sherwood, GJ., 1989. M A T Z I J - - a basic program to determine paleomagnefic remanence directions using principal component analysis. Computers, Geosciences, 15(7):1173-1182. The demagnetization data are displayed using the standard orthogonal projection. The operator can select a series of points which make up a single component of magnetization. These points are redisplayed and a 3-D 'best-fit' is calculated using principal component analysis. If a sample has multicomponent magnetization, new points may be selected and analyzed. The results may be printed as a screen-dump during individual stages, listed on a printer, or plotted on a plotter. Geomagnetism Lab., Univ. of Liverpool, P.O. Box 147, Liverpool L69 3BX, UK.

90:2164 Ram Babu, H.V. et al., 1989. MAGTRAN: a computer program for the transformation of magnetic and gravity anomalies. Computers, Geoseienees, 15(6):979-988.

90:2167 Shreyder, A.A. at~d V.M. Vorob'yev, 1988. Detailed geomagnetic investigations of the Ninetyeast Ridge near the Equator. Oceanology (a translation of Okeanologiia), 28(4):465-467.

Magnetic anomalies depend on the inclination and declination of the Earth's field in addition to the parameters of the source, hence it is difficult to make a qualitative comparison of the magnetic anomaly with the gravity anomaly. Poisson's relation provides a method of transforming magnetic anomalies into gravity anomalies and vice versa for bodies in which the ratio of intensity of magnetization to density remains constant. Potential field transformations provide an elegant method of comparing gravity and magnetic anomalies over the same area and may allow greater information to be derived about their causative bodies than would be possible if the techniques were treated in isolation. Here we present MAGTRAN, a computer program to perform these transformations. This program is executable directly on a VAX-II/750 computer. Natl. Geophys. Res. Inst., Hyderabad 500 007, India.

Linear zonal field characteristics identified in the Ninetyeast Ridge north of the Equator are regarded as having paleomagnetic significance. The paleoanomalies are identified. The difficulty of treating the ridge as a product of a hotspot is discussed. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

90:2165 Robinson, Enders and Dean Clark, 1989. Basic seismology. Elasticity: Cartesian fields of rotation. Leading Edge, 8(11):18-21. In this continuation of the 'Basic Seismology' series, divergence and curl--the two basic differential operators used on vector fields--are discussed. (Divergence was more fully covered in the last tutorial; here, the emphasis is on curl, explained by way of the work integral.) The way is now open to describing the distinctly and separately propagating normal and tangential elements of the seismic wavefield. (fcs)

90:2168 Valet, J.-P., L,isa Tauxe and Bradford Clement, 1989. Equatorial and mld-latilalde records of the last geomagnetic reversal from the Atlantic Ocean. Earth planet. Sci. Letts, 94(3-4):371-384. Three records of the Matuyama-Brnnhes reversal have been obtained from ODP deep-sea cores distributed along the West African margin in the Atlantic Ocean. q~hese studies in addition to the record from DSDP Site 609B provide a latitudinal transect extending from the Equator to 50~ Simulations of natural smoothing by post-depositional processes show that characteristic features of a transitional field geometry dominated by axisymmetry should be preserved in the records, especially at the Equator. The results do not favour the hypothesis that axisymmetrieal terms would dominate during this transition. Cir. des Faibles Radioact., Ave. de la Terrasse, 91198 Gif sur Yvette Cedex, France. 90:2169 Wannamaker, P.E. et al., 1989. Magnetoteiluric observations across the Juan de Fuca subduction

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D. Submarine Geology and Geophysics

system in the EMSLAB project. J. geophys. Res, 94(B 10): 14,111-14,125. A magnetotelluric transect has been obtained near Int. 45~ from the Juan de Fuca spreading center, across the subduction zone and volcanic arc, to the back arc Deschutes Basin. Land observations which are probably related to subduction are a peak in impedance phase of the transverse magnetic mode with a corresponding inflection in apparent resistivity that is continuous eastward from the seacoast and ends abruptly at the High Cascades, signifying an electrically conductive layer in resistive lower crust or mantle with layer conductance decreasing from the coast to the Coast Range, then increasing east of the Willamette Basin. Conversely, ocean floor soundings exhibit a smooth progression from the coast to the spreading ridge, indicating that measurements are reflecting large-scale tectonic structures. Approaching the coast, impedance and vertical magnetic field responses appear increasingly affected by a thick wedge of sediments and thinning of seawater. Univ. of Utah Res. Inst., 391-C Chipeta Way, Salt Lake City, UT 84108, USA. 90:2170 Wannamaker, P.E. et al., 1989. Resistivity cross section through the Juan de Fuca subduction system and its tectonic implications. J. geophys. Res, 94(B 10): 14,127-14,144. A resistivity cross section to depths > 2 0 0 km has been derived from magnetotelluric observations along a profile near 45~ from the Juan de Fuca spreading center to the back-arc Deschutes Basin. Seafloor measurements indicate very low resistivity in the eastward thickening sedimentary wedge of the Cascadia Basin. In the oceanic upper mantle moderately low resistivities presumably reflect up to several percent partial melt attending regional upwelling near the ridge. Under the Oregon Coast Range, a low-resistivity layer dips inland at ~ 2 0 ~ Its conductance,decreases from the coast to about 60 km inland and its position coincides with the plate subduction decoUement. Inland there is a much stronger subhorizontal conductor which may indicate the massive breakdown of greenschist minerals liberating their water well before the volcanie arc is reached. Univ. of Utah Res. Inst., 391-C Chipeta Way, Salt Lake City, UT 84108, USA. 90:2171 Yamazaki, Toshitsugu, 1989. Paleomagnetlsm of Miocene sedimentary rocks around Matsushlma Bay, northeast Japan and its implication for the time of the rotation of northeast Japan. J. Geomagn. Geoelect, 41(6):533-548. Geol. Survey

335

of Japan, 1-1-3 Higashi, Tsukuba, Ibaraki 305, Japan. 90:2172 Young, C.T. and M.R. Kitchen, 1989. A magnetotelludc transect in the Oregon Coast Range. J. geophys. Res, 94(B10):14,185-14,193. Dept. of Geol. Engng, Geol. and Geophys., Michigan Tech. Univ., Houghton, MI 49931, USA. 90:2173 Zlotnicki, Victor and J.G. Marsh, 1989. Altimetry, ship gravimetry, and the general circulation of the North Atlantic. Geophys. Res. Letts, 16(9): 10111014. Gravity accelerations estimated from satellite altimetric mean sea surfaces are compared to ship gravity measurements. Ship gravity measurements are closer to an estimate based on least squares collocation, orbit perturbations, altimetry and terrestrial gravity than to an estimate based on Fourier transforms, orbit perturbations and altimetry only. Both altimetric estimates yield a smoothed picture of the geostrophie component of sea surface currents in the North Atlantic when gravity acceleration data from only nine cruises are subtracted from the altimetric gravity. Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA 91109, USA.

D210. Heat flow 90:2174 Bodri, B., S. Iizuka and M. Hayakawa, 1989. Modeling of deep temperatures and heat flow in central Honshu, Japan. J. Geodynarn, 11(2):105129. Results of a numerical study of deep temperatures and heat flow at depth over an area of almost 100,000 kin 2 in central Honshu are presented. The region represents a boundary zone of three plates-the Pacific, Philippine Sea, and Eurasia--and there are many refraction profiles available in the region. Temperature calculations were made along six transects with a total length of ~ ! 5 0 0 km. In zones of low surface heat flow, temperature at the Moho amounts to 350-500~ and may exceed 1000~ in areas of very high heat flow. Regional variations of Moho heat flow range from 15-20 to 60-70 m W m -2, suggesting the existence of the asthenosphere at depths as shallow as 50 km in zones of high heat-flow anomalies. Geophys. Res. Group, Hung. Acad. Sci., Dept. of Geophys., Eotvos Univ., Budapest I083, Hungary.

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90:2175 Verzhbitskiy, Ye.V., I.M. Sborshchikov and P.P. Shilovskiy, 1988. Heat flux and geology of the Tyrrhenian Sea. Oceanology (a translation of Okeanologiia), 28(4):498-501. Geothermal data and published data on the heat flux of the Tyrrhenian Sea are analyzed. The thermal field is related to the principal tectonic structures of the basin. Distribution of the heat flux indicates that the initial stage of rifting is occurring in the central basin of the Tyrrhenian Sea. Shirshov Inst. of Oceanol., Aead. of Sei., Moscow, USSR. 90:2176 Von Herzen, R.P. et al., 1989. Heat flow and the thermal origin of hot spot swells: the Hawaiian Swell revisited. J. geophys. Res~ 94(B10): 13,78313,799.

New heat flow measurements (150) and many in-situ thermal conductivity determinations obtained at eight sites along a 1230-km-long profile across the Hawaiian Swell (~700 km ESE of Midway Island) reveal no systematic variation in heat flow across the axis of the swell. The anomalous heat flow associated with the swell is probably of the order of 5-10 m W m -2 and may not exist at all. A previous investigation (Von Herzen ct at., 1982) may have overestimated the magnitude of the anomaly and heat flow anomalies associated with the Bermuda Rise, and Cape Verde Rise may also be smaller than previously estimated. Dynamic support, accompanied by a temperature increase of <100~176 confined to the lower lithosphere and underlying asthenosphere, would explain the height of the swell and its small heat flow anomaly. WHOI, Woods Hole, MA 02543, USA.

D 2 4 0 . Local or

regional tectonics

90:2177 Allemand, Pascal et al., 1989. Symmetry and asymmetry of rifts and mechanism of lithosphere thinning. Bull. Soc. g~ol. Fry (8)5(3):445-451. (In French, English abstract.) Experiments to investigate the response of smallscale, multi-layered models to localized stretching under normal gravity conditions show that rifts are largely asymmetric with :respect to extensional deformation at depth. Localized stretching at depth is favored by the presence of a brittle layer in the ductile lower part of the models and results in multiple rifts in the brittle upper part. The experimental results are discussed with regard to geolog-

OLR (1990)37 (4)

ical features. Dept. Sci. Terre, ENS Lyon, UA734, 46 Allee d'Italie, 69364 Lyon cedex, France. 90:2178 Chrry, Jean et al., 1989. Strain localization in rift zones (case of a thermally softened lithosphere): a finite element approach. Bull. Soc. gdol. Ft, (8)5(3):437--443.

The thermal and mechanical evolution of continental lithosphere under extensional forces is studied by a numerical approach of finite elements. Me: chanical and thermal equations are solved simultaneously using temperature dependent rheologies. Extension is initiated by passive rifting on a thermally softened lithosphere. Preliminary results indicate that the initial perturbation should affect the upper lithosphere to concentrate strain in the rift area. During extension the concentration of strain critically depends on conductive cooling in the upper lithosphere and advection of hot material at the base. Ctr. geol. et geophys., Univ. Sei. et Tech., 4 place E. Bataillon, 34060 Montpelier cedex, France. 90:2179 Coulbourn, W.T., P.J. Hill and D.D. Bergersen, 1989. Machlas Seamount, western Samoa: sediment remobilization, tectonic dismemberment and subduction of a guyot. Geo-Marine Letts, 9(3):119-125. Machias Seamount, located about 140 km south of Savaii, rises to <700 m depth, and is situated on the NE flank of the Tonga Trench where depths reach 7700 m. A bathymetric and side-scan sonar survey shows that faults aligned parallel to the local strike of the Tonga Trench dissect the trench-facing half of the guyot. Faults are absent and sediment flows are radially distributed on the NE-facing flank of the guyot. Sediment flow is pervasive on the trenchfacing slope, but not radial because the neo-tectonic fabric controls resedimentation. Hawaii Inst. of Geophys., Univ. of Hawaii, Honolulu, HI 96822, USA. 90:2180 Kleinrock, M.C. and R.N. Hey, 1989. Detailed tectonics near the tip of the Galapagos 95.50W propagator: how the lithosphere tears and a spreading axis develops. J. geophys. Res~ 94(B 10): 13,801-13,838. A model for propagation of an active spreading axis into preexisting lithosphere is developed based on studies conducted near the tip of the propagator growing westward at ~ 5 2 km/m.y, along the E-W trending Galapagos spreading axis. Initial rifting appears to be accommodated along reactivated

OLR(1990)37(4)

D. SubmarineGeologyand Geophysics

faults at the 'tectonic tip.' Extension leads to downdropping of a keystone block cut by normal faults and fissures. Although on a scale of 106 yr propagation is mostly continuous, rifting at the tectonic tip appears discontinuous at a scale of ~1500 m or 30,000 yr. The scale of discontinuity of propagation of the neovolcanie axis is 3-5 km or 50,0(D-100,000 yr. The extension involved in rifting is ~10-20%, and values approximately double if simple shear listric faulting is dominant rather than pure shear normal faulting. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA. 90:2181 Kleinrock, M.C. and R.N. Hey, 1989. Migrating transform zone and lithospheric transfer at the Galapagos 95.5"W propagator. J. geophys. Res, 94(B10): 13,859-13,878. At the 95.5~ propagator system along the CocosNazca plate boundary, the spreading axis is offset left-laterally about 35 km (HI m.y.). This offset migrates westward 52 km/m.y, relative to points along the nearly east-west trending ridge axis, transferring lithosphere from the Cocos to the Nazca plate as it does so. The required 58 km/m.y, of right-lateral motion across this migrating transform is apparently accommodated by an ~15 to 20kin-wide zone of shear deformation dominated by eastward curving of E-W structures to a NW-SE trend. This pattern of curvature, the coinciding zone of high seismicity, and the abundance of talus in the area suggest that shear is distributed over this entire zone. The deformation is inferred to be taken up by a 'bookshelf' mechanism whereby fauits oriented at high angles to the shear couple have left-lateral slip antithetic to the right-lateral shear couple, rotating individual blocks clockwise. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA. 90:2182 Kleim-ock, M.C., R.C. Searle and R.N. Hey, 1989. Tectonics bf the failing spreading system associated with the 95.5~ Galapagos propagator. J. geophys. Res~ 94(B10): 13,839-13,857. Data from detailed surveys constrain plate boundary geometry and evolution of the failing spreading system associated with the Galapagos 95.5~ propagator system. The failed spreading axis, composed of en echelon basins, extends and ages away from the offset and overlapping doomed/failing axes. Detailed structural and volcanic patterns suggest that this offset may be caused by a progression of jumps near the failing axis, probably in association with the strain/stress field of the propagator system's migrating transform zone. A model bf the zone, which is supported by bathy-

337

metric and magnetic evidence for tectonic elements, implies that in at least some cases paired propagators act together. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA.

90:2183 Koyama, Masato and Hiroshi Kitazato, 1989. Paleomagnetic evidence for Pleistocene clockwise rotation in the Oiso Hills: a possible record of interaction between the Philippine Sea Plate and northeast Japan. Geophys. Monogr. Am. geophys. Un, 50:249-265. A paleomagnetic study was made on Pleistocene strata in the Oiso Hills located along the boundary between the Philippine Sea Plate and the northeast Japan Arc. This study evaluates the sense and amount of the Quaternary deformation associated with the interaction between the plates. We propose and discuss three models of the rotation mechanism: (1) local drag along a major strike-slip fault, (2) regional dextral shear along the plate boundary, and (3) oroclinal bending caused by collision of a buoyant terrane. Inst. of Geosci., Shizuoka Univ., Oya, Shizuoka 422, Japan.

90:2184 McMullen, R.J. Jr. and Bijan Mohraz, 1989. An active thermoelasfic rift mechanism. J. geophys. Res, 94(B10): 13,951-13,960. Finite element solutions for stresses and displacements during rift development are obtained for a variable thickness, elastic lithosphere plate subjected to thermoelastic loading by conductive heating from an axial line source in the asthenosphere. Horizontal restraints are removed at the rift axis to model the transition from a continuous to separated lithosphere plate during rifting. Lithosphere strength envelope curves derived from olivine flow laws are used to determine the elastic lithosphere depth in the solutions. Thermoelastic loading of the lithosphere is proposed as a possible driving mechanism for rift formation which produces separation and transition from continuous to rifted lithosphere plate. Mobil Res. and Develop. Corp., Dallas Res. Lab., P.O. Box 819047, Dallas, TX 75381, USA. 90:2185 Melosh, H.J. and C.A. Williams Jr., 1989. M _eehanies of graben formation in crustal rocks: a finite element analysis. J. geophys. Res, 94(B10): 13,961-13,973. Examination of graben formation shows that the configuration of a pair of antithetically dipping normal faults, a graben, is the energetically most favorable fault configuration in elastic-brittle rocks

338

D. Submarine Geology and Geophysics

subjected to pure extension. Furthermore, the occurrence of synthetic normal faults is indicative of a stress field other than purely extensional or of nonhomogeneous characteristics of the rock. A two-layer model is used to show that graben width is only weakly dependent upon the presence of mechanically distinct layers in the crust and that depth of the initial fault is the major factor controlling graben width. Geosei., Dept. and Lunar and Planetary Lab., Univ. of Arizona, Tucson, AZ 85721, USA. 90:2186 Mishra, D.C., S.B. Gupta and M. Vcnkatarayudu, 1989. Godavari Rift and its extension toward the east coast of India. Earth planet. Sci. Letts, 94(3-4):344-352.

The Godavari basin is divided into the GodavariPranhita, Chintalapudi, and coastal sub-basins. The Godavai-Pranhita sub-basin has the characteristics of a half grabeu with Gondwana sediments up to 7.5 km in thickness. Gravity highs are interpreted as mass excesses along the Moho and within the crust. The high in the basin center is probably a remnant of areal doming. The Chintalapudi basin has faulted margins with 3.0 km of sediments and mass excesses along the Moho and shoulders, suggesting that it is a full graben. The prominent structures of the coastal basin are an ~4.5 km depression and a ridge at a depth of 2-2.5 km. Direction of magnetization is similar to the Lower Deccan Trap which suggests the presence of basin intrusions of that period. Natl. Geophys. Res. Inst., Hyderabad 500 007, India. 90:2187 Patriat, Ph. and L. Parson, 1989. A survey of the Indian Ocean triple junction trace within the Antarctic Plate. Implications for the junction evolution since 15 Ma. Mar. geophys. Res. 11(2):89-100.

The junction b~tween oceanie crust generated at the Southeast Indian Ridge and Southwest Indian Ridge has been studied using a Seabeam swathe bathymetry mapping system and other geophysical techniques between the Indian Ocean triple junction and a point ~500 km southwest. The morphotectonic boundary which marks this trace of the ridgeridge-ridge triple junction is complex and varies with age. Recent theories proposing a cyclicity of volcanic and tectonic processes at this mode of triple junctions appear to be supported by a series of regularly spaced, etl echelon escarpments facing the slow spreading Southwest Indian Ridge axis. Inst. de Phys. du Globe de Padis, Place Jussieu, 75252 Paris cedex 05, France.

OLR (I 990) 37 (4)

90:2188 Searle, R.C. et al., 1989. Comprehensive sonar imaging of the Easter microplate. Nature, Lond, 341(6244):701-705.

Recent GLORIA and SeaMARC II sidescan sonar surveys have imaged virtually the whole of the Easter mieroplate, and revealed unprecedented detail and complexity in its tectonic fabric and history. There is clear evidence of rapid microplate rotation, of rapidly evolving plate boundaries and of complex deformation near the northern and southera microplate boundaries. Dept. of Geol. Sci., Univ. of Durham, South Rd., Durham DHI 3LE, UK. 90:2189 Smoot, N.C., 1989. The Marcus-Wake seamounts and guyots as paleofracture indicators and their relation to the Dutton Ridge. Mar. Geol, 88(12):117-131.

The Dutton Ridge is on the oldest extant oceanic crust (Jurassic) in the NW Pacific and lies on the Pacific Plate. It was probably once in the form of a plateau. Pacific Plate movement was northwesterly for the past 43 m.y., then almost due north into the Cretaceous. However, there is a southwesterly azimuth from the Hawaiian-Emperor elbow to the subduction zone where the Dutton Ridge presently resides. This portion of the Pacific Plate is overprinted by the Marcus-Wake seamounts. Evidence of the SW-striking features including fracture zones, flank rift zones, ridge alignments, and tectonic spreading fabric is shown. The change in spreading direction and consequent fracture zone formation is suggested to have occurred between the formation of the Dutton Plateau and the Marcus-Wake Group (Late Jurassic to Early Cretaceous). It is suggested that fracturing caused the breakup of the plateau to form the Dutton Ridge. Diversified Serv., 201 N. Main St., Picayune, MS 39466, USA. 90:2190 .Taylor, G.K. and John Shaw, 1989. The Falkland Islands: new palaeomngnefic data and their origin as a displaced terrane from southern Africa. Geophys. Monogr. Am. geophys. Un~ 50:59-72.

Thirteen dolerite dikes of Lower Jurassic age from the Falkland Islands yield a mean paleomagnetic pole at 4.4~ 272~ It is hypothesized that the islands were once located some 500 km to the north and rotated anticlockwise 1130~ relative to their inferred Cretaceous position. This interpretation would suggest that the Falkland Plateau is composed of several crustal blocks and that the block containing the islands rotated independently of the others as a result of the separation of the Antarctic

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D. SubmarineGeologyand Geophysics

and Africa plates. Dept. of Geol., Oxford Polytech., Headington, Oxford OX3 0BP, UK. 90:2191 Umhoefer, P.J. et al., 1989. Refinements of the 'Baja British Columbia' plate-tectonic model for northward translation along the margin of western North America. Geophys. Monogr. Am. geophys. Un, 50:101-111. Paleomagnetie data suggest that northern Washington, British Columbia, the Yukon, and southern Alaska--'Baja British Columbia'--was at the paleolatitude of Mexico at --,90 Ma and was in place relative to cratonic North America by ~55 Ma. Terrane-travel analysis based on the fixed hotspot hypothesis shows that the Kula Plate could have driven Baja British Columbia the inferred distance in the interval from 90 to 68 Ma, and a model with a N-S boundary between the Kula and North American plates produces sufficient latitudinal displacement, even when the component of movement parallel to the coast is only 50%. A triple junction analysis shows that the Kula-Farallon-North America triple junction would also move rapidly northward in the wake of Baja British Columbia. Dept. of Geol. Sci., Univ. of Washington, Seattle, WA, USA. 90:2192 Weissel, J.K. and G.D. Karner, 1989. Flexural uplift of rift flank~ due to mechanical unloading of the lithosphere during extension. J. geophys. Res, 94(B I0): 13,919-13,950. A suggestion that uplift of rift flanks results from mechanical unloading of the lithosphere during extension and consequent isostatic rebound is based on two concepts: one, the lithosphere retains finite mechanical strength or flexural rigidity during extension; and two, isostatic rebound of the lithosphere follows when kinematics of extension produce a surface topographic depression deeper than the level to w~ch the lithosphere would subside assuming local isostatic compensation. Because the flexural rebound mechanism explains the observed topography and gravity anomaly over both oceanic and continental extensional domains, rheological differences between the two types may not be important in their overall response to extension. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA. 90:2193 Zhao, Xixi and R.S. Coe, 1989. Tectonic implications of Permo-Triassic paleomagnetic results from north and south China. Geophys. Monogr. Am. geophys. Un, 50:267-283. Earth Sci. Bd., Univ. of California, Santa Cruz, CA, USA.

339

D250. Plate and global tectonics 90:2194 Fu, Rong-shan, 1989. Plate motions, earth's geoid anomalies, and mantle convection. Geophys. Monogr. Am. geophys. [In, 49:47-54. A thermal-convection model constrained on a homogeneous, isoviscous, and internally heated mantle is employed. Correlation between the poloidal component of the velocity of plate motions and the surface-velocity field of convection models associated with the earth's geoid anomalies in the degree and order range of 4 to 6 is about 0.6 and has a maximum value at degree 4. The poloidal motions of plates are either parts of the whole mantle convection or they are caused by viscous drag forces (the rigid lithosphere is independent from the mantle convection). Further work is needed to explain the toroidal motions of plates and their poloidal motions with degree and order 1. Dept. of Earth and Space Sci., Univ. of Sci. and Tech. of China, People's Republic of China. 90:2195 Jurdy, D.M., 1989. Plate kinematic controls on accretion. Geophys. Monogr. Am. geophys. Un, 50:93-100. The uncertainties associated with the assumption of fixed hotspots, or the use of a relative plate motion circuit, are estimated for the Pacific and Farallon plates, reconstructed relative to North America for chron 6, chron 13, and chron 25, with the assumption of a 10 km misfit in magnetic anomaly locations and 50 km for individual hotspots. There is a statistically significant difference (greater for earlier reconstructions) between the reconstructions, because the error ellipsoids do not intersect. Possible explanations are non-fixity of the hotspot framework, or ignorance of a plate boundary that was active over the whole Cenozoic. Dept. of Geol. Sci., Northwestern Univ., Evanston, IL, USA. 90:2196 Marry, J.C. and Anny Cazenave, 1989. Regional variations in subsidence rate of oceanic plates: a global analysis. Earth planet. Sci. Letts, 94(34):301-315. Each plate has been divided into regions bounded by major tectonic features; 32 regions have been considered. Bathymetry corrected for sediment loading has been plotted as a function of crustal age for each region. Except for three regions (W Pacific between 10~ and 40~ North American Plate between 24~ and 38"N and African Plate between 10~ and 24~ where ocean floor older than

340

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80-100 Ma flattens with age, depth increases linearly with age */'. Subsidence rate variations are reported from one region to another. Regional variations in subsidence rate appear linearly related to regional variations in ridge crest topography, shallow ridge subsiding quickly and deep ridge subsiding slowly, suggesting that regional variations in subsidence rate reflect the thermal regime of the mantle beneath mid-ocean ridges. Gr. de Rech. de Geod. Spatiale, Ctr. Natl. d'Etudes Spatiales, 18 Av. Edouard Belin, 31400 Toulouse, France.

90:2197 Miura, Satoshi, Hiroshi Ishii and Akio Takagi, 1989. Migration of vertical deformations and coupling of island arc plate and subducting plate. Geophys.

Monogr. Am. geophys. Un~ 49:125-138. Chebychev functions for space domain and Akima's functions for time domain are used to investigate continuous movements in time and filtered movements in space on the Izu Peninsula of northeastern Japan, where an uplift peak velocity of ~ 1 0 km/yr is found. Investigation of the coupling of the island arc plate and subducting plate reveals that in northeastern Japan the Pacific Ocean side is subsiding, the Japan Sea side is uplifting and a precursory uplift occurred prior to the 1983 Japan Sea earthquake. Fae. of Sci., Tohoku Univ., Sendai, Japan. 90:2198

Royer, J.-Y. and D.T. Sandweli, 1989. Evolution of the eastern Indian Ocean since the Late Cretaceons: constraints from Geosat altimetry. J. geophys. Res, 94(B 10): 13,755-13,782. An improved reconstruction for the tectonic evolution of the eastern Indian Ocean from Late Cretaceous to present is presented using reinterpretations of t,he magnetic anomaly pattern in the Australian-Antarctic and Wharton basins, a compilation of magnetic anomalies in the Central Indian and Crozet basins, and fracture zone lineations derived from Geosat altimeter data. Ten plate reconstructions are proposed. Reconstructions at 11 Ma, 21 Ma, 36 Ma, and 43 Ma confirm that the Southeast Indian Ridge has behaved as a single plate boundary since 43 Ma. Implications of the model for relative motions of India, Australia, and Antarctica on the evolution of the Kerguelen Plateau, Broken Ridge, Labuan Basin, and Diamantina Zone and emplacement of the Ninetyeast Ridge and Kerguelen Plateau over a fixed hotspot are examined. Inst. for Geophys., Univ. of Texas, 8701 Mopac Blvd., Austin, TX 78759, USA.

OLR (1990) 37 (4)

90:2199

Wilson, K.M., M.J. Rosol and W.W. Hay, 1989. Global Mesozoic reconstructions using revised continental data and terrane histories: a progress report. Geophys. Monogr. Am. geophys. Un, 50:1-40. A number of regional terrane reconstructions conflict with inferred global plate history or with data from adjacent regional studies. Global plate tectonic reconstructions have ignored terranes until recently, and as a result are over-simplified. This paper represents a progress report on an attempt to 'marry' Mesozoic global plate reconstructions and terrane analysis to produce examples of a 'third generation' of global tectonic maps. The best approach to such an endeavor involves reiterative intercomparison of all regional data amongst each other and with the evolving global model. It is possible to reconcile seemingly contradictory terrane histories using data reliability weighting, simple plate motions and normal spreading rates. These results demonstrate the applicability of 'third generation' plate history analysis and mapping techniques. Dept. of Geol. Sci., Univ. of Colorado, Boulder, CO 80309, USA. 90:2200

Zoback, M.L. et al., 1989. Global patterns of tectonic slress. Nature, Lond~ 341(6240):291-298. Regional patterns of present-day tectonic stress can be used to evaluate the forces acting on the lithosphere and to investigate intraplate seismieity. Most intraplate regions are characterized by a compressional stress regime; extension is limited almost entirely to thermally uplifted regions. In several plates the maximum horizontal stress is subparallel to the direction of absolute plate motion, suggesting that the forces driving the plates also dominate the stress distribution in the plate interior. USGS, Menlo Park, CA 94025, USA.

D280. Volcanism, magmatism 90:2201

Davis, A.S. et al., 1989. Petrology and age of volcanic-arc rocks from the continental margin of the Bering Sea: impfications for Early Eocene relocation of plate boundaries. Can. J. Earth Sci. 26(7): 1474-1490. Eocene volcanic flow and dike rocks from the Beringian margin have arc characteristics, implying a convergent Early Tertiary history. Extrusive rocks are basalt, basaltic andesite, andesite, and minor dacite and rhyolite. The intrusive is a quartz diorite.

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Chemical and mineralogical compositions are similar to those of modern Aleutian Arc lavas. Early Eocene ages of 54.4-50.2 Ma for the samples are well constrained by K-Ar ages. Studies indicate that prior to the Tertiary subduction was more northerly; around 56 Ma subduction became more westerly and the related volcanism ceased for most of mainland Alaska. However, consistent ages of 54-50 Ma indicate a final pulse in arc-type magmatism during this period of plate adjustment. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. 90:2202 Dupuy, C. et al., 1989. Subducted and recycled lithosphere as the mantle source of ocean island basalts from southern Polynesia, central Pacific. Chem. Geol, 77(I):1-18. The Marquesas, Society and Austral-Cook Islands are composed mainly of alkali basalts, basanites and tholeiites, which have geochemical characteristics typical of ocean island basalts. Lavas from the Marquesas and Society Islands display generally chondritic ratios of highly incompatible trace elements and have higher STSr/~Sr than basalts from the Austral-Cook Islands. This grouping probably reflects differences in the composition of an ancient subducted and recycled lithosphere incorporated into the mantle source. The mantle source of the Austral-Cook Islands basalts contains refractory oceanic lithosphere from which a larger amount of basaltic melt was extracted during subduction. Ctr. Geol. et Geophys., Univ. des Sei. et Tech. du Languedoc, F-34060 Montpelier Cedex, France. 90:2203 Fodor, R.V. et al., 1989. Ti.rich Eocene basaltic rocks, Abrolhos platform, offshore Brazil, 18~ petrology with respect to South Atlantic magmatism. J. Petrology, 30(3):763-786. Seventeen rock samples from the five Abrolhos Islands were ,examined. The rocks were largely Ti-rich basalts, diabase, and cumulates with low percentages of incompatible elements and isotopic compositions similar to those of some South Atlantic islands. The basalts:could originate from a 907o crystallization from a parent picritic liquid located near the base of the Brazilian crust. The overall isotopic and trace element contents of the rock are characteristic of the "enriched' composition of a plume that interacted with depleted mantle. Dept. of Mar., Earth, and Atmos. Sci., North Carolina State Univ., Raleigh, NC 27695, USA. 0abf) 90:2204 Japan Volcanologlcal Society, Y. Katsui, S. Aramaki, S. Matsuo, O. Oshima, T. Tiba and Y.

341

Sawada (editors), 1989. Annual report of the world volcanic eruptions in 1986. Bull. volcan. Eruptions, 26:93pp.

The Bulletin of Volcanic Eruptions has been published by the Volcanological Society of Japan since 1961. The present issue includes information on volcanic eruptions that occurred in 1986. Miscellaneous information on the present status of some volcanoes this year is also included. A voleanologist in each country takes the responsibility of sending information on eruptions in a uniform, quantitative format. The bulletin is issued annually, and attached to the Bulletin of the Volcanological Society of Japan and to the Bulletin of Volcanology. All communications related to the bulletin should be addressed to: Editors, Bulletin of Volcanic Eruptions, Earthquake Research Institute, University of Tokyo, Tokyo 113, Japan. 90:2205 Meyer, P.S., H.J.B. Dick and Geoffrey Thompson, 1989. Cumulate gabbros from the Southwest Indian Ridge, 54~176 implications for magmatic processes at a slow spreading ridge. Contr. Miner. Petrology, 103(1):44-63. Petrographic, mineralogical and chemical data on a suite of gabbros and related rocks from the Southwest Indian Ridge and a model for calculating proportions and compositions of trapped liquid and cumulus phases are presented. Proportions of 9trapped liquid range from 3-15070, values characteristic of adcumulates to mesocumulates. Models of postcumulus crystallization indicate significant enrichment of incompatible elements and buffering of compatible elements in residual trapped liquids. The Southwest Indian Ridge is characterized by low magma supply with small batches of melt that ascend directly to the surface having undergone limited polybaric crystallization or are trapped in shallow crustal magma chambers where they evolve and solidify to form cumulate gabbros. WHOI, Woods Hole, MA 02543, USA. 90:2206 Michael, P.J., R.L. Chase and J.F. Allan, 1989. Petrologic and geologic variations along the Southern Explorer Ridge, northeast Pacific Ocean. J. geophys. Res, 94(B10):13,895-13,918. Mid-ocean ridge basalts (MORB) from the Southern Explorer Ridge segment are moderately to strongly enriched in incompatible elements. Enriched MORB were erupted at the highest and widest part of the segment. Variations in incompatible element enrichment occur over short distances, suggesting that the underlying mantle is heterogeneous on a small

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scale, and precluding the existence of a long-lived, well-mixed magma chamber beneath the robust culmination. Less enriched MORB were erupted along the central part of the ridge; a more continuous magma chamber cannot be ruled out for this section on geochemical grounds. All of the MORB from the ridge segment have undergone significant amounts of fractional crystallization. Dept. of Geosci., Univ. of Tulsa, OK 74104, USA.

90:2207

Pasteels, P. et al., 1989. Timing of the volcanism of the southern Kivu province: implications for the evolution of the western branch of the East African Rift system. Earth planet. Sci. Letts, 94(3-4):353-363. New K - A t datings from the Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages > 1 0 Ma have been obtained. From 10 to 7.5 Ma tholeiitic volcanism predominates; from 7.5 to 5 Ma alkali basalts and differentiates are erupted in localized rifts; and Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkalic basalts about 7.5 Ma would correspond to a major rifting phase and initiation of the Lake Kivu Basin formation. Magma formation is thought related to shear heating combined with adiabatic decompression in ascending diapirs. This implies heating at the lithosphere-asthenosphere boundary as a result of extension. Eenheid Geochronol., Vrije Univ. Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.

90:2208

Reinitz, llene and K.K. Tureldan, 1989. Z-Wl"h/2-~U and 2ZrRa/Z-~I'h fractionatlon in young basaltic glasses from the East Pacific Rise. Earth planet. Sci. Letts, 94(3-4):199-207. Mid-ocean ridge basalt glasses, treated to remove Mn and Fe oxyhydroxide coatings containing U and Th decay chain nuclides from the ambient aqueous environment, show little fractionation of 23~ from 238U but extensive enrichment of 2:6Ra over 2~3Th. Chronometry based on 23~ disequilibrium yields a mean age of 151,000_+55,000 yr (20) for T h - U fractionation from a source region with T h / U = 1.58__.0.43 (20). 226Ra excesses over 23~ indicate an enrichment event more recent than the fractionation of Th from U. 226Ra/Z-~rl'h correlates well with K/U, providing a rough means of estimating the age since eruption of the glasses. Dept. of Geol. and Geophys., Yale Univ., Box 6666, New Haven, CT 06511, USA.

OLR(1990)37 (4) 90:2209

Reuber, Ingrid et al., 1989. K-Ar ages of ophiolites and arc volcanics of the Indus suture zone: clues on the early evolution of the Neo-Tethys. Eclog. geol. Helv, 82/2:699-715. K - A r ages obtained for minerals separated from rocks of the Indus suture zone, the Spongtang ophiolite, and the Dras volcanic arc confirm previous estimates for the formation of oceanic crust at the end of the Triassic or earliest Jurassic and indicate that the Dras volcanics were coeval with the arc series of Kohistan and Tibet. Ages of basic dikes intruded into the ophiolites cluster about 140-125 Ma, suggesting amphibolite-grade metamorphism induced by oceanic thrusting and intrusion of thin basic dikes, and at ~ 1 7 0 Ma, probably the minimum age of ophiolite generation. Amphiboles from the Dras arc were dated at 105-95 Ma, implying that plutons formed immediately following volcanic activity, and at 78.5__.2.9 Ma, indicating another stage of metamorphism in arc terranes. GRECO Himalaya, CNRS, Lab. de geol. stratigr, et struct., 40 ave. du Recteur-Pineau, 86022 Poitiers, France. (hbf) 90:2210

Richards, M.A., R.A. Duncan and V.E. Courtillot, 1989. Flood basaits and hot-spot tracks: plume heads and tails. Science, 246(4926):103-107. Continental flood basalt eruptions have results in sudden and massive accumulations of basaltic lavas in excess of any contemporary volcanic processes. The largest flood basalt events mark the earliest volcanic activity of many major hot spots, which are thought to result from deep mantle plumes. The relative volumes of melt and eruption rates of flood basalts and hot spots as well as their temporal and spatial relations can be explained by a model of mantle plume initiation: flood basalts represent plume 'heads" and hot spots represent continuing magmatism associated with the remaining plume conduit or 'tail.' Continental rifting is not required, although it commonly follows flood basalt volcanism, and flood basalt provinces may occur as a natural consequence of the initiation of hot-spot activity in ocean basins as well as on continents. | by AAAS. Dept. of Geol. Sci., Univ. of Oregon, Eugene, OR 97403, USA. 90:2211 Stoffers, P. et al., 1989. Geology of Macdonald Seamount region, Austral Islands: recent hotspot volcanism in the South Pacific. Mar. geophys. Res~ 11(2):101-112. The hotspot region near Macdonald Seamount consists of at least five other volcanic edifices, each

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>500 m high, in an area 50--100 km in diameter. At the edge of the area there is a marked deepening of seafloor from 3900 to 4000--4300 m. Macdonald Volcano itself stands 3760 m above the surrounding seafloor and has a basal diameter of 45 km. It seems likely that Macdonald will emerge at the surface in the near future. March and November 1986 phreatic explosions on Macdonald erupted fragments of ultramafic and marie plutonic blocks together with basic lapilli. Simple crystal fractionation seems to be controlling the chemical evolution of Macdonald magmas. Geol.-Palaontol. Inst. der Univ. Kiel, Olshausenstr. 40, 2300 Kiel, FRG.

90:2212 Storey, M. et al., 1989. San Qulntin volcanic field, Baja California, Mexico: 'within-plate' magmatism following ridge subduction. Terra Nova, 1(2): 195-202. Trace element and isotope analysis of the spinellherzolite-bearing alkali basalts of the Holocene San Quintfn volcanic province reveal compositions comparable to those from ocean island basalts and characteristic of an asthenospherie source. It is suggested that these lavas formed following cessation of subduction when the San Quintin field was underlain by a 'no-slab window" which would permit the upward passage of diapirs or magmas from the asthenosphere. Dept. of Geol., Univ. of Leicester, LEI 7P,H, UK. (hbf) 90:2213 Woodhead, J.D. and M.T. McCulloch, 1989. Ancient seafloor signals in Pitcairn Island lavas and evidence for large amplitude, small length-scale mantle heterogeneities. Earth planet. Sci. Letts, 94(3-4):25%273. Isotopic data for Pitcairn Island volcanic rocks indicate two markedly different sources, closely related spatially and temporally. The isotopic variability of ~ suite confirms that large amplitude variations can exist over length scales of 10 km. The unusual unradiogenic Pb, Nd, and Sr ratios and radiogenic STSr/SrSr isotopic compositions, lack of strong covanation between isotopic and other geochemical parameters and variable Nb/U ratios lead to the suggestion that the two magma types reflect the presence of variable quantities of ancient subducted oceanic crust and sedimentary material in the mlintle source beneath Pitcairn. The complementary trace element abundance patterns often noted between ocean island basalts and island arc tholeiites are seen as a direct result of this subduction zone 'processing'. Res. School of Earth Sci., Australian Natl. Univ., Canberra, ACT 2601, Australia.

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D290. Crust, mantle, core 90:2214 Abrajano, T.A. Jr. and J.D. Pasteris, 1989. Zambales ophiolite, Philippines. II. Sulfide petrology of the critical zone of the Acoje Massif. Contr. Miner. Petrology, 103(i):64-77. Argonne Natl. Lab., CMT-205, Argonne, IL 60439, USA.

90:2215 Boillot, Gilbert et al., 1989. Undercrusting by serpentinlte beneath rifted margins. Nature, Lond, 341(6242):523-525. The west Galicia passive margin (Spain) is bounded by a continuous belt of serpentinized peridotite. We present the results of petrological studies of the peridotite, 39Ar-~ dating of high-temperature ductile sheafing of a dioritic dyke crossing the peridotite and regional seismic stratigraphy which demonstrate that the oplift, ductile sheafing and pervasive serpentinization of mantle rocks occurred at Early Cretaceous time, during the rifting stage of the margin. Our results from the Galicia margin indicate that the seismic crust beneath rifted margin may include mantle material transformed into serpentinite by syn-fift hydrothermal activity. In some cases, the undercrusting process might explain the young age and mobility of the Moho beneath stretched continental basement. Lab. de Geodynam. Sous-Mar., Observ. Oceanol., BP 481, 06230 Villefrancbe sur Mer, France.

90:2216 Bryndzia, L.T., B_I. Wood and HJ.B. Dick, 1989. The oxidation state of the Earth's sub-oceanic mantle from oxygen thermobarometry of abyssal spinel peridotites. Nature, Land, 341(6242):525526. W e use oxygen thermobarometry of abyssal spinel peridotites, representative of most of the Earth's mid-ocean-ridge systems, to show that the redox state of the sub-oceanic mantle lies at values of up to 4 log units (average of 1.35 log units) more reduced than FMQ (fayalite-magnetite-quartz) reference oxygen fugacity buffer. Results are in excellent agreement with oxygen fugacities of MORBs obtained from Fd+/Fe ~+ ratios of quenched glass in pillow basalts, confirming the redox state of the MOP, B source region and suggesting that MORB glasses (as opposed to the cores of pillow basalts) have not undergone significant oxidation (hydrogen degassing) during their ascent. Dept. of Geol. Sci., Northwestern Univ., Evanston, IL 60208, USA.

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90:2217 Coward, M.P. and Bruce Trndgili, 1989. Basin development and basement structure of the Celtic Sea basins (SW Britain). Bull. Soc. gdol. Fr, (8)5(3):423-436. The Mesozoic grabens of western Britain, analyzed using commercial seismic and deep BIRPS data, show basin development and inversion where the gross structure is largely dependent on earlier Caledonian or Variscan thrusts. The basins are filled with thick sequences of syn-rift sediments, but contain little post-rift material. Basin kinematics change across the major tear faults. The Cardigan Bay basin in the north follows the Wernicke model of extension with stretched lower lithosphere offset from faulted upper plate rocks, while Celtic Sea basins are closer to the McKenzie model with a broad zone of lower lithosphere spreading beneath narrow graben which concentrate upper crustal stretch. Geol. Dept., Imperial Coll., London, SW7 2BP, UK. 90:2218 Craglietto, A. et al., 1989. Anelastie properties of the crust in the Mediterranean area. Geophys. Monogr. Am. geophys. Un, 51:179-196. The single-station multimode method for the estimation of Q is applied to earthquakes recorded in the Mediterranean area. The eastern Po Valley, characterized by a thick sediment cover, has a high Q, up to 1000, whereas the north-central Adriatic and the Alps have medium Q values of about 500. The Apennines, the Rhinegraben, the Tyrrhenian Sea, and the Mediterranean region between Crete and southern Italy are characterized by low Q values, 80-100, in the upper 20-25 km of the crust; Q values increase to 250-300 in the lower crust except in the Rhinegraben and the Tyrrhenian Sea, where a Q of ~ 1 0 0 seems to characterize the whole lithosphere. Ist. di Geodesia e Geofisica, Univ. di Trieste, 1-34100 Trieste, Italy. 90:2219 Davis, J.L. et al., 1989. Assessment of Global Positionin~ System measurements for studies of crustal deformation. J. geophys. Res, 94(B10): 13,635-13,650. The 'long-term' precision of Global Positioning System (GPS) determinations is investigated by examining the scatter of relative position, and 'long term" accuracy is investigated by comparing estimates of relative position obtained from GPS data to estimates obtained from independent techniques. The GPS data were obtained over a 2-yr period from a variety of networks of different scales of length.

OLR (1990)37 (4)

The experimental procedure, handling of recorded data, and data analysis are described, and results are presented in terms of time series of estimates for each component of each independent line occupied. Analyses of error are also presented and compared to results obtained from independent techniques. USGS, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025, USA. 90:2220 Dyment, Jrrrme, 1989. SWAT [South-West Approaches Traverse] and the Celtic Sea basins: relations with the Variscan crust, recent formation of the Moho. Bull. Soc. gdol. Fr, (8)5(3):477-487. (In French, English abstract.) SWAT deep Seismic reflection profiles in the Celtic Sea area show the large, deep north Celtic Sea basin, the narrow, shallow south Celtic Sea basin, and many Variscan thrusts. In contrast to Gibbs' (1987) model, the data support a symmetrical, stretching model. The SWAT profiles show a reflection pattern and crustal structure similar to that in the neighboring North Sea and Bay of Biscay. Gravimctric modelling shows good correspondence between observed and computed anomalies. The main features of the resulting depth section are the flatness of the Moho and relative isopacity of the lower crust. Lab. Geophys. Mar., Ecole et observ, de Phys. du Globe, 5 rue Rene Descartes, 67084 Strasbourg cedex, France. 90:2221 Ensley, R.A., 1989. Seismic interpretation. Analysis of compressional- and shear-wave seismic data from the Prudhoe Bay field. Leading Edge, 8(! 1):I0-13~ A comparative analysis of compressional- and shear-wave seismic data for a traverse across the Prudhoe Bay field in Alaska with the lithologic sequence that has been established by drilling, demonstrates that although it is not possible to determine exact lithologies on the basis of velocities and travel times through a given interval, it is possible to use velocity data to establish the gross lithology of a depositional sequence. The data can also be used for estimates of shear-wave anisotropy and thickness of permafrost. Exxon Co., Intl., Houston, TX, USA. 0abf) 90:2222 Fountain, D.M., 1989. Growth and modification of lower continental crust in extended terrains: the role of extension and magmatic underplating. Geophys. Monogr. Am. geophys. Un~ 51:287-299. Extension rate, amount of lithospheric extension and

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the temperature of the underlying asthenosphere exert a strong control on the evolution of the lower continental crust in extended terrains. In the extreme case upwelling of asthenosphere causes accretion of mafie magmas to the base of the crust (magmatic underplating) thereby raising temperatures to values high enough to drive granulite facies metamorphism, anatexis, migmatization and to also increase the ductility of the lower crust during extension. There will be little growth or modification of the continental lower crust for low extension rates, small extension or low asthenosphere temperatures. Extended lower crust will exhibit a high degree of diversity reflecting the relative importance of these parameters. Dept. of Geol. and Geophys., Univ. of Wyoming, Laramie, WY 82071, USA. 90:2223 Green, A.G. et al., 1989. A 'GLIMPCE' [Great Lakes International Muitidisciplinary Program on Crustal Evolution] of the deep crust beneath the Great

Lakes. Geophys. Monogr. Am. geophys. Un., 51:65-80. Geol. Survey of Canada, Ottawa, ON KIA 0Y3, Canada. 90:2224 Green, H.W. II and P.C. Burnley, 1989. A new self-organizing mechanism for deep-focus earthquakes. Nature, Lond, 341(6244):733-737. A range of mechanisms has been proposed for deep earthquakes, including plastic instabilities, shearinduced melting and instabilities" accompanying recrystallization or polymorphic phase transformation. Each of these proposed mechanisms has exhibited certain inherent weaknesses. Here we report experimental observations of high-pressure faulting of metastable Mg2GeO4 olivine as it undergoes incipient transformation to a spinel structure. We present a model in which this faulting arises from the generation, propagation and linking-up of spinel-filled anticracks. When applied to the olivine~spinel transformation in the Earth's mantle, the anticrack model satisfactorily accounts for the similarities and differences between shallow and deep earthquakes and removes the problems associated with frictional sliding. Dept. of Geol., Univ. of California, Davis, CA 95616, USA. 90:2225 Hansen, R.A., Hilmar Bungum and Alfred Alsaker, 1989. Three recent larger earthquakes offshore Norway. Terra Nova, 1(3):284-295. Although there have been no destructive earthquakes on the Norwegian continental shelf in historical time, the occurrence of three M = 5 events between February 1986 and January 1989 may

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represent a recent surge of seismic activity. Calculated focal plane mechanisms place the three earthquakes on N--S to NNE-SSW striking fault planes and imply a NW-SE compression of apparent plate tectonic origin. NORSAR, PO Box 51, N-2007 Kjeller, Norway. 0abf) 90:2226 Henry, W. et al., 1989. A seismic refraction study of the crustal structure of the south Kenya Rift. Geophys. Monogr. Am. geophys. Un, 51:169-172. The explosion part of the Kenya International Seismic Project (KRISP 85) consisted of a 50 km E-W line of stations between Mt. Margaret and Ntulelei, along which shallow information was obtained, and a 200 km N-S line from Lake Baringo to Susua, which supplied most of the information on deep structure. The data from this pilot experiment suggest that there is considerable crystalline basement relief, a reflector at 12-13 km depth, which coincides with the brittle-ductile transition inferred from hypocenters, and a high velocity layer at 22-23 km, which may be due to mafic intrusions or cumulate residue from siliceous volcanics. Phase C_q travel time and amplitude behavior restricts the Moho depth to 34_ 2 km. Dept. of Geol., The Univ., Leicester LEI 7RH, UK. 90:2227 Herak, Marijan, 1989. Hyposearch---an earthquake location program. Computers, Geosciences, 15(7): 1157-1162. Geophys. Inst., Univ. of Zagreb, Horvatovae bb, 41000 Zabreb, Yugoslavia.

90:2228 Ivins, E.R., 1989. New aspects of rotational dynamics within the North Amc~ric~l-eacifie ductile shear zone. Geophys. Mortar. Am. geophys. Un, 50: 179-201. A theory is developed for interplate shear that extends the continuum rotation model of McKenzie and Jackson (1983) to include spatially isolated, theologically 'stiff' zones. The extended theory suggests that a sufficiently robust and ubiquitous interplate shear operating on an oblique subducted lithospheric fragment can provide the energy necessary to put the attached crust above into rapid rotational motion. Calculations predict Plio-Pleistocene clockwise rotation rates of 2~176 which are consistent with estimates of Plio-Pleistocene rigid motion of the western Transverse Ranges and with estimates based on volcanic flows found in the eastern Transverse Ranges. Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA, USA.

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90:2229 Kaneshima, Satoshi and Masataka Ando, 1989. An analysis of split shear waves observed above crustal and uppermost mantle earthquakes beneath Shikoku, Japan: implications in effective depth extent of seismic auisotropy. J. geophys. Res, 94(B10): 14,077-14,092

southwest Germany; other geophysical studies including radiogenic heat production, electromagnetics, magnetism, and gravity; and studies of geological processes operative in extended terranes, granulite terranes, phase transformations, and geochemistry of Rb, Sr, and REE. (hb0

The faster shear waves are polarized nearly in E-W at the stations in the central part of Shikoku, and in NEN-SWS at the southern stations. The arrivals of slower shear waves polarized orthogonally to the faster ones are also clearly recognized in many seismograms at one of the stations. Observations are successfully explained in terms of crustal anisotropy generated by vertical alignment of stress-induced microcracks. The difference in polarization directions suggests that the tectonic stress state beneath the southern Shikoku region is significantly different from that beneath the central part of Shikoku. A quantitative analysis of travel time differences suggests that the seismic anisotropy which causes the observed shear wave splitting is limited to the upper 10 or 15 km of the crust; nevertheless, the possibility that anisotropy is concentrated in a much thinner surface layer cannot be ruled out. Earthquake Res. Inst., Univ. of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo ! 13, Japan.

90:2232 Neprochnov, Y.P., 1989. Study of the lower crust and upper mantle using ocean bottom seismographs. Geophys. Monogr. Am. geophys. Un, 51:159-168.

90:2230 Marillier, F. and J. Verhoef, 1989. Crustal thickness under the Golf of St. Lawrence, northern Appalachlans, from gravity and deep seismic data. Can. J. Earth Sci, 26(8):1517-1532. Geol. Survey of Canada, Bedford Inst. of Oceanogr., P.O. Box 1006, Dartmouth, NS B2Y 4A2, Canada. 90:2231 Mereu, R.F., Stephan Mueller and D.M. Fountain (eds.), 1989. Properties and processes of Earth's lower crust. [Papers from IUGG Symposium U7, Vancouver, August, 1987.] Geophys. Monogr. Am. geophys, Un, 51:338pp; 29 papers. Recent large-scale seismic projects in Australia, Europe, the U.S., and Canada were highlighted at the symposium. The volume is divided into five parts which describe results from various approaches to lower crust exploration: near-vertical reflection experiments providing data on large-scale lentieles, dating, styles of deformation, laterally persistent seismic characteristics, and crustal extension; refraction/wide-angle reflection experiments over the Lake Superior midcontinent rift system, SW Germany, the Deccan Traps and the Koyna area of India, the South Kenya Rift, and other structures; seismic studies of the Kenya Rift Valley, the Mediterranean, the northern Alpine Foreland, and

A review of Soviet seismic data indicates: (1) the presence of layer 3B under the Shatsky and Hess rises, whereas only a few sites in the Pacific Basin show layer 3B; (2) the absence of layer 3A in the studied area of the Brazil Basin; (3) lateral variation of crustal structure in the central Indian Ocean is correlated to the intraplate deformation. Analyses show a smaller layer 3 thickness in the Indian Ocean basin (3.8 kin) than in the basins of the Pacific (4.7 km). The variations in crustal structure are in good agreement with the global tectonic cycles, particularly with variations of seafloor spreading. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow 117218, USSR. 90:2233 Neprochnova, A.F. and N.A. Shishkina, 1989. Crustal models for basins of the Atlantic and Indian oceans. Int. GeoL Rev~ 31(5):478-483. Published data on seismic sections of ocean basins were examined by statistically analyzing seismic velocities and layer thicknesses to develop characteristic crustal models of the basins. It was found that the basin layers follow three general models in the Atlantic Ocean and five in the Indian Ocean. Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

(hb0 90:2234 Novelo-Casanova, D.A., 1989. Comparison of the quality factor for coda and oceanic S waves in the western Pacific lithosphere. Bull. seism. Soc. Amy 79(5): 1642-1644, Measurements of Qc (coda Q) based on the multiple-scattering model of Gao et al. (1983) agree with estimates of Q, (oceanic S) for oceanic waves propagating in the western Pacific lithosphere. Since Qc is easier to measure than Q, this result is particularly important. Inst. de Geofis., Univ. Nac. Auton. de Mexico, Ciudad Univ., Mexico, D.F., Mexico. 90:2235 Okino, Kyoko et al., 1989. The horizontally lying slab. Geophys. Res. Lefts, 16(9):1059-1062.

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An unusual earthquake (mb = 6.2) occurring in the Izu-Bonin Island region in July 1982 at 545 km depth, was clearly separated from the main inclined seismic zone by ~ 2 0 0 km. P-wave travel times for the event, as well as for two events in the inclined seismic zone, were computed using a 3-D ray-tracing program and compared with observations at stations in western Japan. The observations are consistent with a model of a horizontal slab lying on top of the 650-km discontinuity. Disaster Prevention Res. Inst., Kyoto Univ., Uji, Kyoto, 611, Japan. 90:2236 Olsson, Rune and Klaus Meyer, 1989. The P. velocity in a dipping Moho. J. Geodynam., 11(2):99-103. Seismol. Inst., Uppsala, Sweden. 90:2237 Omar, G.I. et al., 1989. Fission-track analysis of basement apatites at the western margin of the Gulf of Suez rift, Egypt: evidence for synchronelty of upfift and subsidence. Earth planet. Sci. Letts, 94(3-4):316-328. Fifty-six apatite fission-track ages and 52 horizontal confined track-length measurements are reported from Precambrian crystalline rocks along the western margin of the Gulf of Suez. On the basis of apatite fission track ages and their length distribution, the data fall into three age groups of from 43 to 385 m.y., 23 to 31 m.y., and 11 to 20.5 m.y. It is proposed that onset of rift-flank uplift occurred between 21 and 23 m.y. ago. Fission-track analysis in combination with subsidence data indicate that commencement of basement uplift postdates the start of rifting and is evidence for passive rifting contemporaneous with and related to extension and subsidence at the Gulf of Suez. Dept. of Geol., Univ. of Pennsylvania, Philadelphia, PA 19104, USA. 90:2238 Potter, CA., 1989. The deep structure of North American,accreted terranes from deep 'seismic reflection data. Geophys. Monogr. Am. geophys. Un~ 50:203-208. Deep seismic data from North American accreted terranes show either relatively simple patterns related to imbrication and underplating of accreted terranes with a uniform sense of vergenee, or very complex intersecting patterns of dipping reflections. Such complex patterns are often difficult to interpret because reflections cannot be traced directly to the surface, and because of ambiguities in interpretation of surface structure. However, reflection patterns in north-central Washington suggest that a major reversal in vergenee in Mesozoic thrust structures occurs on either side of an accreted Jurassic arc. On

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some seismic sections from the Appalachians and the Cordillera, it is clear that terrane boundaries do not remain as important crustal structures, but are quite rapidly overprinted by deep crustal magmatie and deformational processes that accompany crustal extension. Dept. of Geol., Lafayette Coll., Easton, PA 18042, USA. 90:2239 Recq, Maurice, 1989. [Contribution to the study of the deep structure of the Crozet Bank (southern Indian Ocean). I Mar. Geol, 88(1-2):133-144. (In French, English abstract.) The interpretation of gravity anomalies on Ile aux Cochons and Ile de la Possession combined with marine geophysical data collected in the surrounding regions of the southern Indian Ocean shows that the crustal thickening observed below the Crozet Bank is caused by a >12-km thick layer 3 which precludes local Airy-type compensation of the Crozet Bank. The isostatic compensation is mainly achieved by lower density material within the upper mantle down to a depth of 50 kin; compensation level is 60 km deep. A long-wavelength heat flow anomaly observed over the eastern region of the Crozet Plateau indicates that the lower density of the upper mantle is of deep thermal origin within the lithosphere. Dept. de Geol. Dynam., Univ. P. et M. Curie, 4 place Jussieu, 75252 Paris Cedex, France. 90:2240 Rial, J.A., 1989. Seismic wave resonances in 3-D sedimentary basins. Geophys. J. int, 99(1):81-90. Resonant eigenfrequencies, calculated through the use of high-frequency asymptotics, are valid for the areas near the geometrical centre of the basin, where sediment thickness is greatest. The modes of oscillation of trapped seismic waves can be easily computed from simple formulas that relate the geometry of the basin to the type of resonant mode and to the eigenfrequencies. All results are approximations based on WKB solutions to the wave equation whose phase function satisfy resonant or "quantum' conditions inside the basin. Comparison with published numerical data indicates that this approach may be of more general application than the empirical formulations proposed previously. MacCarthy Geophys. Observ., Univ. of North Carolina, Chapel Hill, NC 27599-3315, USA. 90:2241 Rieard, Yanick, Christophe Vigny and Claude Froidevaux, 1989. Mantle heterogeneities, geoid, and plate motion: a Monte Carlo inversion. J.

geophys. Res. 94(B 10): 13,739-13,754.

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A series of tests are performed using a selection of available data for internal loads (tomography and slabs) and state-of-the-art dynamic Earth models with a purely radial viscosity distribution. A straightforward Monte Carlo inversion procedure is established in order to investigate as large a variety of viscosity values as possible. Predictions of each model are compared with the real geoid and plate velocity divergence for degrees between 1 and 6. The best fitting models out of some 60,000 are then selected and discussed. Dept. de Geol., Ecole Norm. Sup., 24 rue Lhomond, 75231 Paris Cedex 05, France. 90:2242 Sauber, Jeanne, Michael Lisowsld and S.C. Solomon, 1989. Geodetic measurement of deformation east of the San Andreas Fault in central California. Geophys. Monogr. Am. geophys. Un, 49:71-86. Dept. of Earth, Atmos., and Planet. Sci., MIT, Cambridge, MA 02139, USA. 90:2243 Semenov, G.A. and A.A. Buravtsev, 1988. Density dependence of elastic wave velocity in deep-sea cores of the Atlantic Ocean. Oceanology (a translation of Okeanologiia), 28(4):468-470.

Combined analysis of geophysical logging data and laboratory measurements obtained during deep-sea drilling in the Atlantic Ocean permits the identification of new correlations between velocity and density in basaltic and sedimentary rocks. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. 90:2244 Thatcher, Wayne, 1989. Earthquake recurrence and risk assessment in circum-Pacific seismic gaps. Nature, Lond, 341(6241):432-434.

Well-documented case histories of repeated rupture of the same segntent of circum-Paeific plate boundary are characterized. Variability in fault slip and spatial extent of great earthquakes rupturing the same plate boundary segment is typical rather than exceptional but sequences of major events fill identified seismic gaps with remarkable order. Earthquakes are concentrated late in the seismic cycle and occur with increasing size and magnitude. Furthermore, earthquake rupture starts near zones of concentrated moment release, suggesting that high-slip regions control the timing of recurrent events. The absence ot major earthquakes early in the seismic cycle indicates a more complex behavi o u r for lower-slip regions, which may explain the observed cycle-to-cycle diversity of gap-filling sequences. USGS, Menlo Park, CA 94025, USA.

OLR (1990) 37 (4)

90:2245 Todd, B.J. and I. Reid, 1989. The continent-ocean boundary south of Flemish Cap: constraints from seismic refraction and gravity. Can. J. Earth Sci, 26(7): 1392-1407.

Seismic-refraction results and gravity modelling suggest that thinned continental crust extends 25 km seaward of the shelf break. The transition from continental to oceanic crust with a main crustal layer P-wave velocity of 7.3 km/s extends seaward over 100 km to the south. One refraction profile with thin ( ~ 4 km) oceanic crust was probably shot on, or very near, the trace of a fracture zone. This study suggests that an oblique shear margin may have formed south of Flemish Cap, possibly as a result of transcurrent motion between Flemish Cap and Iberia during the Cretaceous. Ctr. for Earth Resour. Res., Dept. of Earth Sci., Memorial Univ. of Newfoundland, St. John's, N F A I B 3X5, Canada. 90:2246 Verma, R.K. and K.A.V.L. Prasad, 1989. Gravity field, deep seismic sounding and nature of continental crust underneath NW Himalayas. Geophys. Monogr. Am. geophys. Un, 51:279-284.

As a result of the Cretaceous-Eocene collision of the Indian and Eurasian plates, there has been at least 300 km of crustal shortening along major Himalayan thrusts and 65-75 km of crustal thickening. An analysis of the gravity field in the northwestern Himalayas and Kohistan region throws some light on how the crustal thickening has taken place. A brief summary of this study is presented. It is observed that the Moho increases from a depth of about 30 km near Gujranwala to 60-65 km over the higher Himalayas, north of the Kashmir Valley. The results do not support continental underthrusting as a mechanism for thickening of the crust beneath the higher Himalayas. Indian School of Mines, Dhanbad, India.

D330. Oil and gas 90:2247 Glasmann, J.R. et al., 1989. Diagenesis and hydrocarbon accumulation, Brent sandstone (Jurassic), Bergen High area, North Sea. Am. Ass. Petrol. Geol. Bully 73(11):1341-1360. UNOCAL Sci. and Tech. Div., 376 S. Valencia Blvd., Brea, CA 92621, USA. 90:2248 Mudford, B.S. and M.E. Best, 1989. Venture gas field, offshore Nova Scotia: case study of over-

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D. SubmarineGeologyand Geophysics

pressuring in region of low sedimentation rate. Am. Ass. Petrol GeoL Bull, 73(11):1383-1396. Greenstone Geophys. Res., 5523 Sebastian Place, Halifax, NS B3K 2K5, Canada.

D340. Manganese nodules, etc. 90:2249

Baturin, G.N. et al., 1988. Composition of ironmanganese and sulfide nodules in sediments of the Baltic Sea. Oceanology (a translation of Okeanologiia), 28(4):478-481. SEM studies of a collection of Fe-Mn macro- and micronodules and tubular pyrite nodules established that the ore material of Fe-Mn nodules is structureless and that of pyrite nodules is crystalline. Chemical, atomic absorption and neutron activation analyses indicate that in addition to Fe and Mn, the elements Mo, Cd, Ag, As, P, Au and Zn accumulate to greater degrees in the nodules than in the sediments, but in the sulfide nodules As and Au accumulate along with Fe and S. Shirshov Inst. of Oceanol., Acad of Sci., Moscow, USSR. 90:2250 Ishikawa, Masanori et al., 1989. Cobalt-rich manganese crust on a seamount south of the Marcus Island. J. Fac. mar. Sci. Technol, Tokai Uni% 28:57-73. (In Japanese, English abstract.) Seabottom photographs show that cobalt-rich manganese crusts are widely exposed on the upper slope of flat-topped Seamount T, south of Marcus Island. Chemical analyses of eight dredgings from the seamount indicate that manganese nodules from seafloor shallower than 2050 m contain :>0.5 wt.% cobalt, and that the manganese crust from water depths shallower than 2900 m characteristically has three distinct layers and a central core of olivine pseudomorph clinopyroxene basalt. 90:2251 Kashintsev, G.L., V.N. Sval'nov and Z.T. Novikova, 1988. Composition of the cores of iron-manganese nodules in the northern Atlantic Ocean. Oceanology (a translation of Okeanologiia), 28(4):482-486. Based on their physical and genetic features, the nodules are assigned to the sedimentational Mn-Fe type (Canary Basin) and Fe-containing type (Guyana Basin). They are enriched in Fe, Co and Pb and impoverished in Mn, Ni, Cu and Zn. The cores of the nodules from the Canary Basin consist primarily of peridotite, gabbro, dolerite and metamorphic rock. The great predominance of peridotite and

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gabbro indicates that blocks of oceanic crust underwent considerable displacement, bringing the third and fourth layers of the crust to the surface. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. 90:2252 Skornyakova, N.S. and V.N. Zaikin, 1988. Local variability of iron-manganese nodules in the eastern Clarion-Clipperton ore province. Oceanology (a translation of Okeanologiia), 28(4):487491. Variations in the productivity, form and dimensions of nodules with essentially constant chemical composition were found in the eastern part of the Clarion-Clipperton ore province. The diagenetic and sedimentational nodules in the area were enriched in Cu, Ni, Zn and Mo. The variability in productivity, morphology and dimensions is associated with instability of sediment accumulation, fluctuations in currents, and rates of accumulation and mixing of the upper semifluid layer of sediments. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

D360. Books, collections (general) 90:2253 Booker, J.R. and A.D. Chave ct al., 1989. Special section: the EMSLAB-Juan de Fuca Experiment. J. geophys. Res, 94(B!0): 14,093-14,283; 14 papers. Electrical properties provide a window on processes that are of great interest in understanding earth. Electromagnetic induction, which can image electrical properties, hashndergone a major revolution in the last decade. The EMSLAB [Electromagnetic Study of the Lithosphere and Asthenosphere Beneath] experiment, the largest electromagnetic induction study to date, has been a significant factor in this revolution. It has substantially advanced data processing and interpretation of electromagnetic induction data. It has also imaged conductive structure associated with subduction, volcanism, and continental accretion that provide important constraints on the role of fluids in these processes. Finally, EMSLAB has made significant contributions to the use of electromagnetic methods in physical oceanography. The effort and its results are documented in these fourteen papers. 90:2254 Cohen, S.C. and Petr Vanf~ek (eds.), 1989. Slow deformation and transmission of stress in the Earth. [Symposium papers from the I U G G 20th

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D. SubmarineGeologyand Geoph.ysics General Assembly Meeting, Vancouver, August t987.1 Geophys. Monogr. Am. geophys. Un, 49:138pp; 13 papers.

This monograph treats quasi-static deformation due to gravitational, rheological, thermal, chemical and phase-change stresses. The preface provides a thumbnail description of each of the papers which deal with a wide variety of slow deformation phenomena: post glacial rebound; episodic creep in mantle deformation; the Earth's fossil bulge; relations between plate motion, geoid anomalies, and mantle convection; coupled interactions of rigid lithosphere and deformable fault zones; microblock rotations; and plate motions as revealed by vertical movements in NE Japan, Washington state and SW British Columbia, Lake Balaton in Hungary, the Indo-Gangetic plains, the Kalawar area of India, and the Diablo Range of California. (hb 0 90:2255 Coward, M.P. and B. Trudgill et al., 1989. Extensional basins. Part 1I. Bull. Soc. gdoL "Fr, (8)5(3):423-532; 9 papers. (In French, English abstracts.) 90:2256

de Moustier, Christian (guest editor), 1989. Special issue on bathymetry and seafloor acoustic remote sensing. IEEE Jl ocean. Engng, 14(4):285-374; 9 papers. These papers provide an overview of advances made during the last decade in mapping seafloor morphology and the attendant problems of data storage and processing. Three contributions consider various aspects of instrumentation: principles of operation, depth errors, geometric effects, and acoustic interferences, as well as the first results of a new multibeam echo-sounder, ECHOS XD. Another paper suggests ,the use of artificial intelligence techniques for constructing a correctly registered bathymctric chart. Four papers treat terrain characterization on various scales using a variety of instrumentations and parameters. A final paper uses seafloor acoustic backscatter data to obtain a

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measure of backscattering strengths over varying topography and bottom materials. (hb0 90:2257 llillhouse, J.W. (ed.), 1989. Deep structure and past kinematics of accreted terranes [Papers from IUGG Symposium I2, Vancouver, 15-18 August 1987.] Geophys. Monogr. Am. geophys. Un., 50:283pp; 16 papers. This monograph focuses on both tracking displaced terranes using paleomagnetics, geologic mapping and paleontology and the nature of the deep structure underlying the terranes as revealed by seismological, geochemical, and potential-field methods. Two general papers consider global Mesozoic reconstructions and plate kinematic controls on accretion; another six present paleomagnetic and seismic data and models of the changing paleogeography of the western margin of North America; the remainder describe the probable distribution of individual terranes found in the southern Andes, Falkland Islands, Guerrero (Mexico), Europe, the Appalachians, and north and south China at various times in the geologic past. 0abf) 90:2258 Ward, L.G. and G.M. Ashley (eds.), 1989. Special issue. Physical processes and sedimentology of siliciclastic-dominated ingoonai systems. Mar. Geol, 88(3-4):181-364; 9 papers. This volume, an outgrowth of a 1986 SEPM symposium held in Raleigh, North Carolina supplies information on the wide variety of coastal lagoons which have developed under temperate and arid climates, for the most part during Pleistocene and Itolocene time. The initial papers on hydrodynamic and sedimentologic processes operative in lagoons are followed by studies which emphasize stratigraphic relationships and the changes effected by rising and falling sea levels. Examples presented include barrier and lagoon systems studied in Ireland, Nova Scotia, Maine, North Carolina, Tunisia, the Delmarva Peninsula (Virginia), and southwest Florida. A final paper interprets the deposits of the Upper Cretaceous Rock Springs Formation in southwest Wyoming. (hbt)