Century- to millennial-scale sedimentological-geochemical records of glacial-Holocene sediment variations from the Barra Fan (NE Atlantic)

The Barra Fan, located at the continental margin of NW Scotland, offers a u nique possibility to retrieve records of exceptional high resolution to obt ain climate records on a century-millennial timescale. We used a sedimentol ogical-geochemical approach to examine the sediment variations that reflect the palaeoceanography and climate history of the area. Inorganic chemistry combined with micropalaeontology reveals trends and changes in NE Atlantic palaeoceanography and northwest European climate at the sub-Milankovitch f requency. This study builds on results from two British Geological Survey c ores and one giant piston core (Core 57/-11/59, Core 56/-10136 and Images C ore MD95-2006) that were obtained during the NEAPACC (NE Atlantic Palaeocea nography, Special Topic NERC) phase. Geochemical records of lithogenic inpu t fluctuate rapidly and their patterns parallel sea surface temperature and particle size records. The cold periods are characterized by increased cla y input compared to the warm periods. The Younger Dryas period and other pr ominent periods such as the equivalent of Heinrich Event 1, show extremely expanded sections up to several metres in thickness. Enhancement of accumul ation rates in the glacial section is due to the influence of downslope sed imentation, meltwater deposition; and large-scale currents redistributing t he sediment along the upper slope. The radiochemical tracer (excess Th-230) shows that major shifts in terrigenous sediment supply were extremely rapi d over the last 15 ka. The shifts in terrigenous supply occurred over time- spans of less than a century. Century-scale events of lithogenic input can be visually correlated to other North Atlantic climate records such as the GISP2 Greenland ice core delta(18)O record for the last 15 ka, although the resolution of radiocarbon dating of these events in the sediments is not s ufficiently precise to verify that the visual correlations are correct. The particle flux and biogenic records show sawtooth-shaped cycles opposite to the Dansgaard-Oeschger cycles.