Bransfield Basin fine-grained sediments: late-Holocene sedimentary processes and Antarctic oceanographic conditions

Abstract

The Antarctic Peninsula is sensitive to climatic change due to its northerly position and to the relatively reduced volume and character of its ice cover. High-resolution palaeoclimatic records from the Ant arctic Peninsula ice cores extend back only 500 years. A climatic record of 2850 years in the Bransfield Basin is investigated through the analysis of sediment gravity cores from the floor of the central subbasin (core GEBRA-1) and the slope of the eastern subbasin (core GEBRA-2). Sedimentological, mineralogical and geo chemical properties have been systematically measured, together with Accelerator Mass Spectrometry (AMS) radiocarbon dating. The fine-grained sediments result from two main processes: hemipelagic settling from resuspensions and primary productivity, and turbidity currents. Hemipelagic sediments were selected to investi gate the oceanographic and climatic conditions of the northern Antarctic Peninsula region during the last three millennia. Cold climatic periods are characterized by millimetric laminations and/or black layers with higher organic carbon, nitrogen and opal contents. Warm periods are recorded as massive to diffuse laminated facies with lower biogenic contents. The results include the ‘Little Ice Age’ (LIA) cold pulse as well as several 200– 300 year long fluctuations within the LIA and before this major climatic event of the Holocene.