OLR (1985) 32 (12) D. Submarine Geology and Geophysics 1029

deformed trench fill bounded by landward dipping thrust faults, separated by a d6collement surface from an underlying ~ l -km- th ick unit of nearly undeformed trench fill, which along with oceanic lithosphere is being underthrust to act as a buffer between offscraped sediment and oceanic basement. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. (hbf)

85:7155 McGinnis, L.D., R.H. Bowen, J.M. Erickson, B.J.

Allred and J.L. Kreamer, 1985. East-west Ant- arctic boundary in McMurdo Sound. Tectono- physics, 114(1-4):341-356.

Western McMurdo Sound is capped by a thin veneer of layered reflectors. The absence of deep, layered reflectors suggests the crust is made up primarily of intrusions associated with plutons generated during the Ross Orogeny. Reflection data support earlier interpretations that indicate fundamental differences in the crust beneath McMurdo Sound and the Transantarctic Mountains, perhaps due to Early Paleozoic subduction of the Ross Embayment crust beneath the Transantarctic Mountains. Orogeny has produced an over-thickened crust beneath the Ross orogenic belt which was followed by several periods of reactivation including the Jurassic thermal event and the Early Tertiary uplift of the Transantarctic Mountains. Presence of the McMurdo Volcanics and preliminary data interpretations suggest that the sound is now being thinned by extension. Dept. of Geol., Louisiana State Univ., Baton Rouge, LA 70803-4101, USA.

85:7156 Rangin, C., J.F. Stephan and C. MUller, 1985.

Middle Oligocene oceanic crust of South China Sea jammed into Mindoro collision zone (Phil- ippines). Geology, geol. Soc. Am., 13(6):425-428.

A summary is provided of the Cenozoic evolution of Mindoro, an island south of Luzon, located at the 'complex junction between the Manila Trench and the collision zone of the North Palawan block with the western Philippines mobile belt. ' The age equivalence of Amnay ophiolites and the oldest Middle Oligocene magnetic anomalies of the South China Sea Basin is cited as evidence that the ophiolites may be a piece of South China oceanic crust rotated 20 ° counterclockwise and caught between the San Jose-North Palawan block and the Mindoro-Luzon basement. LA 215, CNRS, 4 ave de Bois Preau, 92506 Rueil-Malmaison Cedex, France. (hbf)

85:7157 Srivastava, S.P., 1985. Evolution of the Eurasian

Basin and its implications to the motion of Greenland along Nares Strait. Tectonophysics, ! 14(1-4):29-53.

Analysis shows that the Eurasian Basin and Nor- wegian-Greenland Sea started to evolve at about anomaly 25 time, though active seafloor spreading did not start until anomaly 24 time. Spreading in the Eurasian Basin has been a result of motion only between the North American and Eurasian plates since the beginning, with the Lomonosov Ridge remaining attached to the North American Plate. From Late Cretaceous to Late Paleocene, Greenland moved obliquely to Ellesmere Island; most of this motion was taken up within the Canadian Arctic Islands resulting in little or no motion along Nares Strait. From anomaly 25-21 Greenland continued to move obliquely, resulting in a displacement of 125 km along and of 90 km normal to the Nares Strait. From Mid-Eocene to Early Oligocene another 100 km of motion took place normal to the Strait. Atlantic Geosci. Centre, Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada.

85:7158 Stagg, H.M.J., 1985. The structure and origin of

Prydz Bay and MacRobertson Shelf, East Ant- arctica. Tectonophysics, 114(l-4): 315 -340.

Multichannel seismic and magnetic data indicate that much of Prydz Bay is underlain by a sedi- mentary basin that is at least 5 km thick and probably represents a failed rift. The sediments are little disturbed by folding and faulting and contain three major unconformities of Triassic-Early Juras- sic, Early Cretaceous, and Mid-Miocene-Ear ly Pliocene age. These probably represent rift onset, margin breakup, and glacial advances, respectively. Bur. of Mineral Res., P.O. Box 378, Canberra City, ACT 2601, Australia. (amt)

85:7159 Sweeney, J.F., 1985. Comments about the age of the

Canada Basin. Tectonophysics, 114(1-4): 1-10.

The Canada Basin appears to have formed over a 60 Ma interval during the Cretaceous period. Conti- nental breakup was widespread ~131 113 Mya along what was to become the polar margin of North America, and seafloor formation was active during an extended Cretaceous interval ~118-79 Mya. Data indicate that all parts of the North American polar margin could have formed at about the same time. Relatively less/slower stretching occurred along the segment southwest of Brock Island and relatively more/faster stretching took place along the