The sedimentary structure in the western Weddell Sea

Abstract

Abstract The western Weddell Sea was one of the regions where breakup of Gondwana was initiated about 180 Ma. The perennial ice coverage makes it difficult to obtain knowledge about the thickness and structure of the sediments that might reveal information about the break-up process and the evolution of the Weddell Sea Basin. Seismic investigations south of 66°S provide a first detailed view of the sediment structure of the westernmost Weddell Sea. In addition, four wide angle seismic measurements with offsets up to 31 km were undertaken. The sediment thickness ranges from 4.8±0.3 to 7.3±0.3 km, but seems to be relatively uniform in the area between the eastern continental margin of the Antarctic Peninsula (at 52°W) and 35°W. Three out of four measurements of the sediment thickness in this area are between 4.8 and 5.7 km. The depth of the acoustic basement is constrained by both the wide angle data and by seismic reflection profiles acquired at the same time. A comparison of the two western wide angle seismic measurements with estimates for the non-magnetic overburden derived from aeromagnetic data show a deviation of more than 1 km. The depth velocity functions reveal that the sediments of the western Weddell Sea are divided into two sequences that are separated by a broad transition zone at a depth of 6–7 km.