| Summary: | The Upper Rhine Plain is part of a Cenozoic graben, which is approximately 40 km wide and 300 km long. This geological structure determines the geometry and the thicknesses of the Quaternary sediments, with a subsiding central zone and loess-covered alluvial terraces on its margins. In Alsace, most of the recorded Paleolithic remains are concentrated on the margins while the central area appears to be devoid of occupation. Recent investigations have been carried out in the region within the framework of the PaleoEls Project, and in the course of rescue excavations. They indicate that the sedimentary deposits, which are locally very thick, pose an obstacle for studying archaeological sites and are partly responsible for the observed distribution pattern. However, they also provide a chronological and palaeoenvironmental framework for the Middle Paleolithic. For the Upper Pleistocene, loess sequences attest to the establishment of pine forests during the first half of the period (from approximately 100,000 to 70,000 years ago), phases of erosion around the middle of the period (from approximately 100,000 to 30,000 years ago) and significant levels of deposition which fossilize tundra gleys over the course of the second half of the period (from approximately 30,000 to 20,000 years ago). Loess sequences also indicate environmental conditions that were dryer and richer in biodiversity than those in northern France. Around Strasbourg, alluvial clayey loams, more than 20 m deep, indicate the existence of a flood plain occupied by wet meadowlands and few trees during Pleistocene interstadial or interglacial times that was conducive to human occupation. While these deposits are currently only accessible through coring, Late Glacial and Holocene formations, which are easy to study, can serve as a model for studying the more discontinuous records from the earlier periods. They show the tendency for shrinkage in that part of the plain submitted to flooding from the Pleniglacial to the recent Holocene, leading us to envisage ...
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