High-resolution 3D seismic exhibits new insights into the middle-late Pleistocene stratigraphic evolution and sedimentary processes of the Bear Island trough mouth fan

Abstract

Arctic Ocean trough mouth fans (TMFs) represent a valuable archive of glacial-interglacial sedimentary processes that are especially important when reconstructing pre-Weichselian glaciations that may lack distinct imprints on the shelves. In 2011, we acquired the first high-resolution 3D seismic cube (~3 m vertical and 6 m horizontal resolution) on the continental slope of the SW Barents Sea by use of a P-Cable 3D system, to study in detail the seismic stratigraphy and glacial depositional history of the Bear Island Trough Mouth Fan. This technology provides data with a resolution that, for the first time on the western Barents Sea slope, enables detailed mapping of deposits of different glacial cycles. The dataset provides entire spatially coverage, allowing us to reconcile multiple generations of glacigenic deposits and channel systems. High-resolution 3D seismic data is crucial to describe buried channels, glacial units, as well as low relief landforms such as sediment waves accurately. The 30 km2 seismic cube is located at the southern flank of the Bear Island TMF at water depths from 592 to 660 m where sandwaves dominate the present seafloor. The data covers the glacially derived stratigraphy in the uppermost ~700 m below the seafloor. We establish a robust stratigraphic framework by interpreting seismic reflectors along 2D tie-in lines to previously well-constrained seismic and well data. We find that our data provide a record of progradation of glacigenic debris flows (GDFs) since MIS 12 (0.5 Ma) to present. Horizon slices reveal a range of gullies and channels at different depths overlying the GDFs. We describe the paleoenvironment and sedimentary processes throughout this time-span (that covers seven glacial cycles) and discuss the impact of the Barents Sea Ice Sheet waxing and waning on erosion, sedimentation, and deposition along the continental slope. Abundant buried gullies were hitherto unknown at the Bear Island TMF, with previous work describing this succession as a debris-flow dominated unit where meltwater-related features are lacking, and interpreting this to represent low average temperatures. By use of the relatively small high-resolution 3D seismic dataset, we provide new evidence for the presence of gullies and channels indicating that periods of ice sheet melting and meltwater runoff existed throughout the middle-late Pleistocene succession. The work offers new insight into the stratigraphic evolution of a continental margin dominated by GDFs and demonstrates the value of high-resolution seismic, such as the P-Cable system, in resolving important details of paleo-slope-environments.