Nares Strait—a suture zone: geophysical and geological implications

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D. SubmarineGeologyand Geophysics

D240. Local or regional tectonics 85:7143 Barrier, E., 1985. The two stage collision of Taiwan: an active orogen. Tectonophysics, 115(1-2):167175. Collision of the Hengchun Ridge, an accretionary wedge, with the Chinese continental margin, was followed by collision of the Luzon Trough and volcanic arc, from the Philippine Sea Plate, with the Central Range of Taiwan. During the first stage, strength of the margin induced a decrease of the convergence rate that controlled the final Central Range orientation and induced the second stage of the collision. A reconstruction of the Taiwan collision during the last 4 Ma is proposed. CFR, CEA, CNRS, Ave. de la terrasse, 91 190 Gif sur Yvette, France. 85:7144 Bukovics, Christian and P.A. Ziegler, 1985. Tectonic development of the Mid-Norway continental margin. Mar. Petrol. Geol., 2(1):2-22. Seismic reflection records, exploration well and shallow core-hole data are integrated to prepare a summary of the structural framework of the shelf and slope and the geologic evolution of the MidNorway Basin between 62 ° and 68°N. Devonian and Early Carboniferous wrench movements preceded some 270 My of rifting prior to Early Eocene crustal separation between Greenland and Fennoscandia. Tensional forces appear to have dominated throughout this period; volcanic activity throughout the Late Paleozoic and Mesozoic remained low level. NAM b.v., Assen, Netherlands. (hbf) 85:7145 Craddock, C., E.C. Hauser, H.D. Maher, A.Y. Sun and Guo-Qiang Zhu, 1985. Tectonic evolution of the west Spitsbergen fold belt. Tectonophysics, 114(1-4): 193-211. Dept. of Geol. and Geophys., Univ. of Wisconsin, Madison, WI 53706, USA. 85:7146 Gonzalez-Ferr~in, O., 1985. Volcanic and tectonic evolution of the northern Antarctic Peninsula-Late Cenozoic to Recent. Tectonophysics, 114(14):389-409. Geological, geophysical and geochemical analyses are used to study the tectonic history of the Antarctic Peninsula and adjacent islands. A twostage history is suggested. Active subduction, indicated by a significant volcanic calc-alkaline belt along the northwestern margin of the peninsula, dominated from the Cretaceous to the Upper Miocene. Four cycles of volcanic activity can be

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discerned. This phase was followed by a back-arc extension cycle that continues to the present, creating a 'fan-rift' system that includes the Bransfield, Prince Gustav and Larsen rifts. Petrological differences among the rifts are discussed. Dept. de Geol. y Geofis., Univ. de Chile, Santiago, Chile. (amt) 85:7147 He, Liansheng, 1984. Polycyclic plate tectonic movements and the Cenozoic tectonics of the Sooth China Sea. Bull. Chin. Acad. geol. Sci., 9:65-74. (In Chinese, English abstract.) Three plate tectonic cycles during the Late Cretaceous-Eocene, Oligocene-Miocene, and Pliocene Pleistocene resulted in the formation of the Philippines and Borneo (orogenic activity) and in the formation of the Celebes, Sulu, and South China seas as well as continental fragments of West Zhongsha and Nansha (seafloor spreading activity). Six tectonic stages: rifting, seafloor spreading, plate drifting, convergence, subduction and collision are defined as sea-making (the first three) or orogenic (the last three) movements. South China Sea Geol. Invest. Hdqtrs., Min. of Geol. and Min. Res., People's Republic of China. (msg) 85:7148 Herzer, R.H., J.D. Bradshaw (comment), R.M. Carter and L. Carter (reply), 1985. IComment and reply] 'the Motunau fault and other structures at the southern edge of the Australian-Pacific plate boundary, offshore Marlborough, New Zealand.' Tectonophysics, 115(1-2): 161-166. Based on an analysis of multichannel reflection lines, the authors question the existence of a major fault--the Motunau Fault--that was proposed by Carter and Carter (1982) to form a boundary of the Conway Microplate. They suggest that the region represents a 'zone of widespread dextral shear manifested in many ways and on many scales and not as a single transcurrent fault.' New Zealand Geol. Surv., Lower Hutt, New Zealand. (amt) 85:7149 Jackson, H.R., 1985. Nares Strait--a suture zone: geophysical and geological implications. Tectonophysics, 114(1-4): 11-28. Plate kinematics around the North Atlantic, the Norwegian and Greenland Seas and the Eurasian Basin constrain motion along Nares Strait. The triple junctions are found to be stable. Motion along Nares Strait between anomalies 34 and 13 is a combination of strike-slip and compression. Regional geology supports the plate reconstructions; local Nares Strait

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D. SubmarineGeologyand Geophysics

geology does not refute the predicted motions. Interpreted in terms of the Wilson cycle, the Nares Strait area has the characteristics of a cryptic suture, a join between regions of collided continental crust. Atlantic Geosci. Centre, Geol. Surv. of Canada, Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada. 85:7150 Jongsma, Derk, J.E. van Hinte and J.M. Woodside, 1985. Geologic structure and neotectonies of the North African continental margin south of Sicily. Mar. Petrol. Geol., 2(2):156-179. Marine geological and geophysical data provide evidence that after the breakup of Gondwanaland about 180 My ago the Tripolitania Basin, Jarrafa Trough, Melita Bank, Medina Bank, and the Ragusa-Malta Plateau formed part of a sinking, passive margin. Neocomian-to-Eocene N W - S E rifting and dextral shear were succeeded by pre-Middte Miocene subduction of oceanic crust and Middle Miocene uplift of part of the African margin, and in post-Messinian time by the establishment of a rift and dextral shear zone that extended from the Strait of Sicily to the Medina Ridge in the Ionian Basin. Current activity appears to involve motion of a microplate (which includes Sicily) in response to the eastward movement of the Calabrian Arc and Sicilian block over the last remnant of Eastern Mediterranean oceanic lithosphere. Free Univ., Inst. for Earthsci., PB 7161, 1007 MC Amsterdam, Netherlands. (hbf) 85:7151 Leggett, Jeremy, Yutaka Aoki and Takefumi Toba, 1985. Transition from frontal accretion to underplating in a part of the Nankai Trough accretionary complex off Shikoku (SW Japan) and extensional features on the lower trench slope. Mar. Petrol. Geol., 2(2):!31-141. Results from a grid of 48-fold multichannel seismic lines shot in the Nankai Trough in 1980 and 1981 are presented. The data suggest three distinct physiographic-tectonic domains on the lowermost slope. 'Linear ridges demarking laterally-continuous hangingwall anticlines above ramps in a relatively simple imbricate stack of trench turbidites characterize the western domain. An imbricate fan underlies a relatively flat structural terrace in the east. Between those two domains lies a compound knoll...opposite which the thrust front pushes some 10 km further seaward than...to the east and west.' The data are interpreted to suggest underplating of the overriding plate. To what degree the differences between the three domains are due to differences in the amount of underplating or to the subduction of

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topographic features cannot be resolved by the available data. Dept. of Geol., Imperial Coll. of Sci. and Tech., London SW7 2BP, UK. (amt) 85:7152 Letouzey, Jean and Masaaki Kimura, 1985. Okinawa Trough genesis: structure and evolution of a backarc basin developed in a continent, Mar. Petrol. Geol., 2(2):111-130. Seismic reflection, seismic refraction, drilling, dredging, and geological field data are used to detail the evolution of the Okinawa Trough, which, with the exception of the Andaman Sea, serves as 'the only example of an active marginal backarc basin type opened into a continent at an early stage of evolution.' It is noted that subduction and arc volcanic activity preceded the opening of the backarc basin, and that the opening and subsidence of the trough and tilting and subsidence of the forearc terrace were synchronous. Backarc rifting at both ends of the basin remains active today. The conclusions are used to formulate a new model for the Late Cenozoic development of the Philippine Sea Plate. Inst. Francais du Petrole, I e t 4, ave. de Bois Preau, 92506 Rueil Malmaison Cedex. France. (hbf) 85:7153 Lyberis, Nicolas and Siegfried Lallemant, 1985. The subduction--coilision transition along the outer Hellenic Arc. C. r. Acad. Sci., Paris, (S6r. II)300(17):885-890. (In French, English abstract.) The direction of extension is perpendicular to the trenches along the outer Hellenic Arc and parallel to the border of the compressional zone in Peloponnesus. Near the Mediterranean Ridge and the western boundary of the Peloponnesus margin, westward extension is stopped by a compressional belt. The North-Magne transverse fault zone forms the southern limit of the compressional edge of the Peloponnesus margin. It is proposed that the Europe-Africa collision began north of the NorthMagne fault zone. Dept. de Geotecton.. LA 215, Univ. Paris-VI, 4 place Jussieu, Tour 15, 75230 Paris, France. 85:7154 McCarthy, Jill and D.W. Scholl, 1985. Mechanisms of subduction accretion along the central Aleutian Trench. Geol. Soc. Am. Bull., 96(6):691-701. Migrated 24-fold seismic records provide data on the structure of the Aleutian margin which suggest major modifications of currently accepted models of rising accretionary wedges. The data define an overlying structural unit, consisting of 3 4 blocks of