ABSTRACT: Cenozoic Tectonics and Sedimentation on the Pacific Margin of the Antarctic Peninsula
Robert D. Larter, Peter F. Barker
The Antarctic Peninsula was a magmatic arc subducting Pacific Ocean floor throughout the Mesozoic. During the Cenozoic, subduction ceased at each of a series of ridge-crest trench collisions that migrated north-eastwards along the margin. Physiographically and geophysically the continental shelf to the west of the Antarctic Peninsula can be divided into inner, middle, and outer shelf provinces. On the inner shelf the water depth is mostly less than 250 m and it is underlain by glacially eroded and dissected crystalline arc rocks. The water depth over the middle and outer shelf areas averages about 500 m. Multichannel seismic data show a mid-shelf sedimentary basin or basins of unknown age separated from a prograded outer shelf by a structural high. Age control on the oute shelf sequences is provided by correlation through the continental slope to ocean floor of age known from magnetic anomalies. By this method it can be shown that post-collision sediments exceed 2 km in thickness on some parts of the outer shelf. Seismic stratigraphic analysis of these sequences reveals post-collision uplift, followed by subsidence. The younger sequences (<6 Ma) exhibit a variety of unusual characteristics that suggest they were produced by the action of ice sheets grounded out to the shelf edge at times of glacial maximum. Thus they are thought to contain a direct record of West Antarctic ice sheet fluctuations. Comparison of this record with the record of eustatic sea-level fluctuations derived from seismic stratigraphic studies on low latitude margins would provide insight into the relation between fluctuations in ice volume and global sea-level change.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990