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Bathyal benthic Foraminifera in a piston core from east off the Miyako Islands, Ryukyu Island Arc
oLR (1990)37 (12)
D. SubmarineGeologyand Geophysics
of Archaeol., Univ. of Cape Town, Rondebosch, 7700 South Africa. 90:7086 Ujiir, lliroshi, 1990. Bathyal benthic Foraminifera in a piston core from cast off the Miyako Islands, Ryukyu Island Arc. Bull. Coll. Sci, Univ. Ryu/,3,us, 49:60pp; plus 32 black and white plates. Dept. of Mar. Sci., Univ. of the Ryukyus, Nishihara, Okinawa 903-01, Japan.
D200. Gravity, geodesy, magnetism 90:7087 Moroz, Yu.F., 1988. Deep geoeleetric profile In the Asia-Pacific transition zone. Phys. solid Earth (a translation of Fiz. ZernlO, 24(5):383-386. Based on magnetotelluric sounding and regional heat flow, the electric conductivity of the upper mantle is studied along the Primorye-SakhalinKamchatka-Komandorskiye islands profile. An asthenospheric conducting layer is identified everywhere along the profile; it rises below the Sea of Okhotsk to a depth of 70 km and under Kamchatka to a depth of 50 kin. The asthenospheric protrusion under eastern Kamchatka is associated with an electric conductivity drop to a few ftm, and is reflected on the surface by widespread modern volcanic and hydrothermal activity. Deep faults play an important part in its formation. Inst. of Volcanol., Far "East Sci. Ctr., Acad. of Sci., USSR. 90:7088 Porter, D.L. et al., 1989. The synthetic geold and the estimation of mesoscate absolute topography from altimeter data. Johns Hopkins APL tech. Dig, 10(4):369-379. A 'synthetic geoid' is an estimation of the medium spatial scale variations of the true marine geoid. It is calculated by subtracting from an altimeter-derived mean sea surface an estimate of mean sea-surface displacement obtained from a dynamical ocean model initialized with remotely sensed and in-situ data. Estimates are obtained from Geosat altimetric data using a synthetic geoid and are compared with observations and model results. This method is compared with results obtained by differencing sea-surface heights along individual tracks from the altimetric mean sea surface and with those obtained by differencing two individual repeat tracks from each other. Excellent results are obtained. Space Geophys. Grp., APL, Johns Hopkins Univ., Laurel, MD 20707, USA.
I III
90:7089 Rochette, Pierre and G.L. Nord Jr. (eds.), 1990. Special section. Application of optical and magnetic techniques in rock magnetism. Geophys. Res. Letts, 17(6):765-798; 8 papers. The eight papers here are representative of those contributed to a symposium on the subject held during the Sixth General Assembly of the International Association of Geomagnetism and Aeronomy at Exeter (England) in July of 1989. They document advances in the sophistication of magnetic measurements at high and low temperatures that characterize magnetic grains, the integration of high resolution imaging and chemical instrumentation, and the more careful and systematic use of rock magnetism parameters to geological applications. (fcs)
90:7090 Suk, D., D.R. Peacor and R. Van der Voo, 1990. Replacement of p)Tite framboids by magnetite in limestone and implications for palaeomagnetism. Nature, Lond~ 345(6276)'611-613. Limestones are an important source of palaeomagnetic data, with magnetite the dominant carrier of the magnetization. Here we present electron microscopy data obtained from a sequence of samples of Onondaga Limestone (northern New York), which unambiguously show that magnetite spheres are derived by alteration and replacement of framboidal pyrite. Remagnetization is thus caused by chemical, rather than viscous, processes. This chemical remanent magnetization is compatible with a fluid-mediated event occurring on a regional scale, induced by tectonic stress of Alleghenian age. Dept. of Geol. Sci., Univ. of Michigan, Ann Arbor, MI 48109, USA. 90:7091 Trigui, Mounir and Alain Tabbagh, 1990. Magnetic susceptibilities of oceanic basalts in alternative fields. J. Geomagn. Geoelect, 42(5):621-636. Susceptibility measurements on over 32 samples of oceanic basalts in a weak uniform alternative field show that multidomain grain basalts exhibit variations clearly different from single domain and pseudo-single domain ones, but in most cases a decrease of in-phase susceptibility with frequency is verified. Except for four samples, the direct proportionality between quadrature susceptibility and the first derivative of in-phase susceptibility with frequency logarithm is also experimentally observed. ENIT, BP 37, Le Belvedere, 1002 Tunis, Tunisia.
D. SubmarineGeologyand Geophysics
of Archaeol., Univ. of Cape Town, Rondebosch, 7700 South Africa. 90:7086 Ujiir, lliroshi, 1990. Bathyal benthic Foraminifera in a piston core from cast off the Miyako Islands, Ryukyu Island Arc. Bull. Coll. Sci, Univ. Ryu/,3,us, 49:60pp; plus 32 black and white plates. Dept. of Mar. Sci., Univ. of the Ryukyus, Nishihara, Okinawa 903-01, Japan.
D200. Gravity, geodesy, magnetism 90:7087 Moroz, Yu.F., 1988. Deep geoeleetric profile In the Asia-Pacific transition zone. Phys. solid Earth (a translation of Fiz. ZernlO, 24(5):383-386. Based on magnetotelluric sounding and regional heat flow, the electric conductivity of the upper mantle is studied along the Primorye-SakhalinKamchatka-Komandorskiye islands profile. An asthenospheric conducting layer is identified everywhere along the profile; it rises below the Sea of Okhotsk to a depth of 70 km and under Kamchatka to a depth of 50 kin. The asthenospheric protrusion under eastern Kamchatka is associated with an electric conductivity drop to a few ftm, and is reflected on the surface by widespread modern volcanic and hydrothermal activity. Deep faults play an important part in its formation. Inst. of Volcanol., Far "East Sci. Ctr., Acad. of Sci., USSR. 90:7088 Porter, D.L. et al., 1989. The synthetic geold and the estimation of mesoscate absolute topography from altimeter data. Johns Hopkins APL tech. Dig, 10(4):369-379. A 'synthetic geoid' is an estimation of the medium spatial scale variations of the true marine geoid. It is calculated by subtracting from an altimeter-derived mean sea surface an estimate of mean sea-surface displacement obtained from a dynamical ocean model initialized with remotely sensed and in-situ data. Estimates are obtained from Geosat altimetric data using a synthetic geoid and are compared with observations and model results. This method is compared with results obtained by differencing sea-surface heights along individual tracks from the altimetric mean sea surface and with those obtained by differencing two individual repeat tracks from each other. Excellent results are obtained. Space Geophys. Grp., APL, Johns Hopkins Univ., Laurel, MD 20707, USA.
I III
90:7089 Rochette, Pierre and G.L. Nord Jr. (eds.), 1990. Special section. Application of optical and magnetic techniques in rock magnetism. Geophys. Res. Letts, 17(6):765-798; 8 papers. The eight papers here are representative of those contributed to a symposium on the subject held during the Sixth General Assembly of the International Association of Geomagnetism and Aeronomy at Exeter (England) in July of 1989. They document advances in the sophistication of magnetic measurements at high and low temperatures that characterize magnetic grains, the integration of high resolution imaging and chemical instrumentation, and the more careful and systematic use of rock magnetism parameters to geological applications. (fcs)
90:7090 Suk, D., D.R. Peacor and R. Van der Voo, 1990. Replacement of p)Tite framboids by magnetite in limestone and implications for palaeomagnetism. Nature, Lond~ 345(6276)'611-613. Limestones are an important source of palaeomagnetic data, with magnetite the dominant carrier of the magnetization. Here we present electron microscopy data obtained from a sequence of samples of Onondaga Limestone (northern New York), which unambiguously show that magnetite spheres are derived by alteration and replacement of framboidal pyrite. Remagnetization is thus caused by chemical, rather than viscous, processes. This chemical remanent magnetization is compatible with a fluid-mediated event occurring on a regional scale, induced by tectonic stress of Alleghenian age. Dept. of Geol. Sci., Univ. of Michigan, Ann Arbor, MI 48109, USA. 90:7091 Trigui, Mounir and Alain Tabbagh, 1990. Magnetic susceptibilities of oceanic basalts in alternative fields. J. Geomagn. Geoelect, 42(5):621-636. Susceptibility measurements on over 32 samples of oceanic basalts in a weak uniform alternative field show that multidomain grain basalts exhibit variations clearly different from single domain and pseudo-single domain ones, but in most cases a decrease of in-phase susceptibility with frequency is verified. Except for four samples, the direct proportionality between quadrature susceptibility and the first derivative of in-phase susceptibility with frequency logarithm is also experimentally observed. ENIT, BP 37, Le Belvedere, 1002 Tunis, Tunisia.