Rhine loess at Schwalbenberg II - MIS 4 and 3

Abstract

The locality Schwalbenberg is situated in the Middle Rhine valley close to the town of Remagen. It exhibits a rather complete section of the Last Glacial loess with good tripartite subdivision of the Lower Pleniglacial (Keldach Formation, MIS 4) with one interstadial soil, excellent subdivision of the Middle Pleniglacial (Ahrgau Formation, MIS 3) with eight interstadial soils, and minor subdivision of the Upper Pleniglacial (Hesbaye and Brabant Formation). A first profile log, Schwalbenberg I, published earlier with organic carbon (Corg) and phosphorus curves, showed that the Middle Pleniglacial Schwalbenberg section represents an excellent mirror image of MIS 3 curves of ice and deep sea cores. This text presents a new profile log from a new wall, Schwalbenberg II, with tighter sampling (6 cm per sample). Grain-size and carbonate curves show the tripartition of smaller coarse silt content and carbonate content in the Keldach Formation, fluctuating coarse silt and carbonate in the Ahrgau Formation and enhanced coarse silt and carbonate in the Upper Pleniglacial. The nine interstadial soils (calcaric cambisols and one calcaric regosol) turn out to be autochthonous due to maxima of organic carbon, minima of carbonate and pedogenic top down intrasol zonation. All gelic gleysols show carbonate maxima. The Corg curve of Schwalbenberg II and δ18O record of the annuallayer counted Greenland GISP 2 core show strikingly good correlation of rhythmicity and magnitude between the Ahrgau Formation and the Greenland interstadials 17 to 5. This correlation is widely confirmed by numerical dating of the Schwalbenberg II section. The boundary Ahrgau Formation/Hesbaye Formation (MIS 3/MIS 2) was drawn so far with the top of the uppermost cambisol (Sinzig 3 Soil). Lithological and chronological data speak for drawing the boundary somewhat higher at the Hesbaye Discordance. Consequently, the Schwalbenberg section misses the soil representing the GIS 5 interstadial. Nevertheless, it presents the most complete Ahrgau Formation (MIS 3) in western Europe. Loess profiles of the more continental region in the northeastern Carpathians or in Siberia are even richer in soils. Copyright: