Seismic stratigraphy along the Amundsen Sea to Ross Sea continental rise: A cross-regional record of pre-glacial to glacial processes of the West Antarctic margin
Abstract The seismic sediment record of the Amundsen Sea continental rise provides insight into the sedimentation processes from pre-glacial to glacial times, variations in ocean-bottom circulation, early ice sheet growth, and intensification towards the present icehouse regime. Seismic reflection data acquired during the 2010 RV Polarstern and the 2006 RV Tangaroa expeditions, created a > 2000 km long continuous Amundsen Sea to Ross Sea seismic transect. Pre-existing lines linked to this transect, connect key seismic stratigraphy horizons from the Ross Sea shelf to the rise and farther along the West Antarctic margin, up to the Amundsen Sea Embayment. Seismic units AS-1 to AS-3 constitute the Cretaceous to Eocene pre-glacial (PG) sequence (79–34 Ma), units AS-4 to AS-6 the Eocene to mid-Miocene transitional (T) sequence (34–15.5 Ma), and units AS-7 to AS-11 the mid-Miocene to Quaternary full glacial (FG) climate sequence (15.5–0 Ma). The top PG sequence boundary horizon AS-u3/uPG-T, links to unconformity RSU6 of the Ross Sea shelf and to the base of Unit II of the eastern Amundsen Sea, and is interpreted as the first arrival of grounded ice on the shelf. The top T sequence boundary AS-u6/uT-FG, links to RSU4 and the base of Unit III, and is interpreted as the onset of the FG regime with intensified ice sheet advances onto the outer shelves. The Amundsen Sea basin accumulated up to 3.9 km thick sediments in its centre. Seismic facies geometry analysis suggests Paleocene–Eocene bottom-current activity, late Eocene shelf grounding of the West Antarctic Ice Sheet, and no apparent difference in the deep-sea sediment transport processes or temporal shift in deposition between the Amundsen Sea and Ross Sea. Implications for a Marie Byrd Land uplift starting at ~ 30 Ma are observed by a progressive change in horizon dip in the central Amundsen Sea seismic sequences.