PLEISTOCENE PERIGLACIAL SLOPE DEPOSITS IN GERMANY – INDICATORS OF CHANGING CLIMATIC CONDITIONS AND SEDIMENTARY PROCESSES DURING THE LAST ICE AGE

The mountainous areas in Germany are largely covered by several different Pleistocene periglacial slope deposits (PPSD) lying on top of each other. The German classification system distinguishes four types of periglacial layers:

* The Basal Layer (BL) occurs in almost every relief position. It consists of debris of the underlying rock. Its thickness varies in a wide range.

* The Intermediate Layer (IL) is usually found on top of the BL. It is rich in loess and only occurs in positions which favour loess accumulation and preservation.

* The Upper Layer (UL) contains rock debris and loess. It shows a thickness of about 50 ± 20 cm.

* The Top Layer (TL) is restricted to certain rock types in higher regions.

Genesis of the PPSD

At the beginning of the Lower Wuermian, erosion led to exposure of unweathered rock. Then, the rock disintegrated into rock debris, which moved downslope by gelifluction, forming a BL. The formation of an IL requires previous deposition of loess. Such deposition took place in cold-dry periods of the Middle and Upper Pleniglacial. Subsequently, a cold-humid phase again led to gelifluction resulting in the formation of the IL. By the end of the Upper Pleniglacial, a phase of erosion, leading to a residual stone enrichment at the surface, is assumed. The upper part of the IL, including the stone pavement, was again affected by three phases of gelifluction during the Oldest, Older, and Younger Dryas, resulting in the formation of the UL. During the last gelifluction phase, the Laacher See Tephra (LST), which was deposited during the Allerød, was mixed into the UL. Remnants of the IL were only preserved in sheltered locations. In all other positions, the IL was partly removed by the phase of erosion mentioned above, and partly incorporated into the UL.