SEISMIC STRATIGRAPHY, TECTONICS AND ICE SHEET CONFIGURATION OF CONTINENTAL MARGIN SEQUENCES IN THE BELLINGSHAUSEN SEA, WEST ANTARCTICA

摘要

Recent advancement in Sequence Stratigraphy indicated that the stratigraphic signature in the Antarctic continental shelf profiles could serve as a gage of tectonics and ice sheet configuration change during the Neogene. To accomplish this purpose, two profiles from the continental shelf off Adelaide Island, Bellingshausen Sea are reexamined. The layers of S4 are recognized at the base of the continental slope as an accretional sediment and at the mid-shelf high as a tectonically uplifted stratum before and during oceanic ridge crest to trench (RC-T) collision. The age of S4 is assigned to be Early Miocene and the RC-T collision occurred in the Middle Miocene. During the following subsidence period in the Late Miocene, S3 and S2 were deposited as seaward progradational sequences in a passive margin condition. The sequence boundary between S2 and S1 was interpreted to be produced by shelf edge grounding of ice sheets after a period of large deglaciation in the Early Pliocene. The boundary corresponds to the time when the levee channel complexes were formed in the slope fan areas. The S1 reflects more frequent ice sheet grounding in the Pleistocene.