Centennial provenance variability during the last glacial maximum revealed by heavy mineral analysis of loess deposits

Loess-Paleosol-Sequences (LPS) are important sedimentary archives that enable to infer climatological parameters during the Quaternary at high temporal resolution. Three isochronous, central European LPS sites were investigated by means of heavy mineral, single-grain sedimentary provenance analysis using an automated, correlative workflow guided by machine learning. The goals of this study are (1) to investigate if regional differences exists between the LPS in terms of heavy mineral composition (2) if local sources can be disentangled from regional ones and (3) if short-lived processes affecting the source-to-sink system are detectable.

The LPS compose a transect from SW to NE Germany. Synchronicity was controlled by presence of the Eltville tephra (ca. 23.2 – 25.6 ka) and/or precise OSL age modeling, confirming sedimentation during the last glacial maximum.

120 silt-sized heavy mineral aliquots were analyzed by microscopy, Raman-spectroscopy and electron microprobe, resulting in a correlated dataset of grain parameters (size, roundness, color, etc.), mineralogy and chemical composition for each grain analyzed.

First results show that the LPS are differentiated based on heavy mineral composition, supporting a Southern, Alpine and Northern, Fennoscandian provenance. Heavy mineral ratios and garnet chemistry reveal abrupt, centennial changes in the Southern and Northern LPS. This points to re-organization of the sediment routing system in the Rhine flood plain at the Southern site. While at the Northern site the advancement of the Scandinavian Ice Sheet probably perturbs the westerlies resulting in short-lived phases of increased deflation from the East.