The Record of Terrigenous Glacial/Interglacial Variability in Core KN223-10LC2 Along the Western Flanks of the Mid Atlantic Ridge.

Core KN223-10LC2 (14° 24.04' N, 50° 37.27' W, Z=4453m) contains 33.9m of carbonate clays gradually alternating in clay content downcore. This core was collected in 2014 during the final long-coring cruise of the R/V Knorr (Shipboard Party, Cruise KN223, 2014). The base of the cored interval is estimated to Pliocene in age and appears to contain a complete section of the Pleistocene glacial/interglacial events. This core site was targeted along a bathymetric high along the flanks of the Researcher Ridge in part to avoid turbidity deposits that commonly occurred along the surrounding abyssal seafloor. Shipboard bulk measurements of gamma ray attenuation (bulk density) and magnetic susceptibility were used to pick glacial and interglacial samples for further analysis of terrigenous component variability. We isolated terrigenous minerals from the bulk sediments using a series of chemical extractions. Once extracted, detailed grain size distributions were performed using an electronic particle size analyzer (Coulter-Counter). Glacial samples generally showed larger and more variable average terrigenous grain sizes while interglacial samples were consistently finer grained. We assume that the terrigenous component in these sediments is predominantly eolian in origin suggesting that regional wind intensity (northern trade winds) varied considerably between glacial/interglacial periods and that this core may provide an opportunity for a detailed, long term study of the eolian contributions throughout the Pliocene and Pleistocene. Stable isotope records will be used to construct a more detailed age model to assess the time series of changes in terrigenous grain size as well as determine terrigenous mass flux.