An evaluation of magnetic basement depth determinations from the southwestern Barents Sea

Abstract

The European program on the Late Cenozoic evolution of the Polar North Atlantic Margins (PONAM), running from 1990 to 1994, resulted in a wealth of seismic data and sediment cores, particularly from the Svalbard and Barents Sea continental margin, but also from areas of the East Greenland margin. Deep sediment coring was undertaken on both margins during ODP Legs 152 and 162. This paper uses the PONAM-generated information as well as previous and subsequent seismic and core data, to review our present understanding of the glacial geological development of these regions.Four main depositional facies have been identified. These are represented by hemipelagic, glaciomarine sediments, sandy, silty debris flows, diamictic debris flows and tills deposited directly beneath grounded ice. The temporal and spatial distribution of these four facies determines the architecture and seismic character of the two continental margins. The two regions show significant differences, with regard to both the timing of initial glaciation and the response of the ice sheets to climatic variability. Glacial deposition has taken place on the East Greenland margin at least since 7 Ma, but apparently only since 2.5 Ma on the Svalbard–Barents Sea margin. Significant glacial expansion across the continental shelf probably occurred in the early and late Pliocene in East Greenland, whereas the glaciers on Svalbard and the Barents Sea did not reach the shelf edge until the early Pleistocene. Despite a shorter glacial period, average glacial sedimentation rates are 2–3 times higher on the Svalbard–Barents Sea margin than on the studied parts of the East Greenland margin. The Svalbard–Barents Sea ice sheet has advanced and retreated much more frequently during the Plio–Pleistocene than the Greenland ice sheet. Glacial regime (polar on Greenland and polythermal to temperate in Svalbard and the Barents Sea) and the more easily erodible preglacial bedrock of Svalbard and the Barents Sea are thought to be main factors responsible for the differences in ice sheet behavior and, consequently, glacial sediment production.