1241 / 2024-09-20 18:07:48

Seismic stratigraphy of the Bellingshausen Sea, Western Antarctica

West Antarctica,Bellingshausen Sea,seismostratigraphy,tectonics

Session 53 - Geological analogues for future warm ocean and climate

Preliminary results of field geophysical (multichannel seismic, magnetic and gravity) studies carried out in the framework of the 69th Russian Antarctic Expedition in April 2024 onboard the R/V “Akademik Aleksander Karpinsky” in the Bellingshausen Sea are presented. Seismic observations were carried out using the DigiSTREAMER 2D with the 6000 m and 600 m long streamer. Three seismic units were identified in the sedimentary cover of the Bellingshausen Sea, which accumulated during the pre-glacial (up to 9.6 Ma) and glacial periods (9.6 - 5.3 and after 5.3 Ma) of the sea basin development. Two major seismic horizonts were identified on seismic sections based on ODP Leg 188 (Sites 1095 and 1096). The one of the major horizons  correlates with the initiation of short-lived ice-advances on the continental shalf at 9.6 Ma. The second major horizon corellates with start of rapidly deposited terrigeneouus sediment transported to the shelf edge by frequent advances of dround ice at 5.3 Ma. According to obtained data two depocenters of post Late Miocene (post-9.6 Ma) sediments were recognized in the Bellingshausen sea. Magnetic data revealed three consequences of spreading magnetic anomalies with ages ranging from Late Cretaceous to Eocene. The continent-ocean boundary to east of 90°W is a paleosubduction zone extending along the foot of the continental slope. On the West Antarctic margin, the convergent regime existed (probably with interruptions) during most of the Phanerozoic time (as evidenced by the age of rocks of the Antarctic Peninsula magmatic arc), ceasing its development in the time interval from 50 Ma to 4 Ma as a result of the northeastward migrating collision of the Aluk Ridge (spreading ridge between the Pacific Plate and the Phoenix Plate) and the Antarctic Plate Trench. West of 90°W, the continental margin is a passive one, which formed under the conditions of crustal extension of the southeastern Gondwana and subsequent separation of the New Zealand continental block from Antarctica in the Late Cretaceous (90-80 Ma).