Abstract. Loess–palaeosol sequences (LPSs) are key archives for the reconstruction of Quaternary environmental conditions, but there is a lack of investigated records from the southern Upper Rhine Graben (southwestern Germany). To close this gap, a LPS at Bahlingen-Schönenberg was investigated at high resolution using a multi-method approach. Infrared stimulated luminescence screening reveals a major hiatus in the lower part of the LPS that according to luminescence dating is older than marine isotope stage (MIS) 4. The section above the hiatus formed by quasi-continuous loess sedimentation between ca. 34 and 27 ka, interrupted by phases of weak reductive pedogenesis. The fact that this pedogenesis is much weaker compared to corresponding horizons in the more northerly part of the Upper Rhine Graben could be due to regionally drier conditions caused by a different atmospheric circulation pattern at the time of deposition. Our results reinforce earlier notions that the major environmental shifts leading into the Last Glacial Maximum (LGM) of southern Central Europe significantly predate the transition of MIS 3 to 2 (ca. 29 ka). In particular, the last massive phase of loess accumulation started several thousand years prior to the arrival of glaciers in the foreland of the Alps, which raises questions regarding the source and transport paths of the dust. It is also noted that no loess dating to the LGM or the time thereafter was observed due to either a lack of deposition or later erosion.
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Abstract. Loess–palaeosol sequences (LPSs) remain poorly investigated in the southern part of the Upper Rhine Graben but represent an important element to understand the environmental context controlling sediment dynamics in the area. A multi-method approach applied to the LPS at Köndringen reveals that its formation occurred during several glacial–interglacial cycles. Field observations, as well as colour, grain size, magnetic susceptibility, organic carbon, and carbonate content measured in three profiles at 5 cm resolution, provide detailed stratigraphical information. Only minor parts of the LPS are made up of loess sediment, whereas the major parts are polygenetic palaeosols and pedosediments of varying development that are partly intersected, testifying to a complex local geomorphic evolution. The geochronological framework is based on 10 cm resolution infrared-stimulated luminescence (IRSL) screening combined with 18 multi-elevated-temperature post-IR IRSL ages. The luminescence ages indicate that two polygenetic, truncated Luvisols formed during marine isotope stages (MISs) 9(–7?) and MIS 5e, whereas unaltered loess units correspond to the last glacial (MISs 5d–2) and MIS 8. The channel-like structure containing the two truncated Luvisols cuts into > 2 m thick pedosediments apparently deposited during MIS 12. At the bottom of the LPS, a horizon with massive carbonate concretions (loess dolls) occurs, which may correspond to at least one older interglacial.
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