Reconstruction of 30 distinct dust and loess events during the last glacial cycle: Quantification of the hemisheric, regional, and local forcing of such weather extremes during the past

点击翻译按钮获取中文摘要

16 long sediment cores from Eifel dry maar lakes have been drilled between 1999 and 2005 by the ELSA project (Eifel Laminated Sediment Archive) and document the time 0 -140 ka. The cores HL2 and EI2 reach the last interglacial, which is characterized by annually laminated sediments (Sirocko et al., 2005; Schaber & Sirocko, 2005). The sediments of MlS2-5c are not annually laminated, but event laminated. These events are turbidites, suspension layers, loess layers and tephra, which are used to correlate the 16 cores (Diss. K. Schaber, in prep.). In this project we will evaluate in detail 30 distinct loess layers, which can be correlated between the cores. Grain size analysis of individual loess layers is done by the automated method of ultra high resolution grain size measurements from thin sections, which was developed by Seelos & Sirocko (2005). The grain size composition of 30 individual loess layers between MIS 5e and MIS1 will be detected in all available cores and will be evaluated for about 20 statistical grain size parameters. Gradients in layer thickness, geochemistry and in the grain sizes composition can then be used to quantify the principle paleo wind direction, i.e from the west or from the east. Westwinds carry fingerprints from Buntsandstein (colour) and Muschekalk (CaCO3) strata, whereas winds from the east erode mainly Devonian shales and magmatic deposits and are different in geochemistry and mineralogy. The principle wind direction provides a first indication about the meteorology that lead to the dust transport. Most likely phenomena are low pressure systems moving across Germany or the adjacent North Sea, downdrafts within mesoscale convective storms and intense orographic flows.