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palaeo trench

900km

Fig. 5.11. Profiles across the western Antarctic Peninsula-Bellingshausen Sea margin (after Ashcroft, 1972; Kimura, 1982). Profile A shows seismic velocities in km sec.-1. The locations of the profiles are shown in Fig. 5.10. On profiles B and C, a 2-way travel time of 1 sec. is equivalent to about 1 km thickness in the sedimentary layers.

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Fig. 5.11. Profiles across the western Antarctic Peninsula-Bellingshausen Sea margin (after Ashcroft, 1972; Kimura, 1982). Profile A shows seismic velocities in km sec.-1. The locations of the profiles are shown in Fig. 5.10. On profiles B and C, a 2-way travel time of 1 sec. is equivalent to about 1 km thickness in the sedimentary layers.

Fig. 5.12. Possible reconstruction of South America to western Antarctica (after Dalziel, 1982). The arrows indicate north directions for the present-day orientation of South America and Western Antarctica.

Cenozoic as a result of subsidence during the early rifting of New Zealand from Antarctica. Tectonism resumed in the Oligocene when extensive eruptions of calc-alkaline volcanic rock (hyaloclastite deposits) of Late Cenozoic age (up to 28 Ma B.P.) occurred (LeMasurier and Rex, 1982). These hyaloclastite deposits are considered to be the product of alkaline volcanic eruption under a continental ice sheet and, along with major normal faulting, suggest an extensional tectonic regime and the existence of a continental ice sheet for the last 28 Ma.

There are few bathymetric or other data across the shelf between Thurston Island and Sulzberger Bay (Vanney and Johnson, 1976), but the limited data

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