Les études géologiques, géomorphologiques menées au cours d'une opération d'archéologie préventive (Parc d'Activités Economiques Intercommunal du Giessen, Scherwiller, Bas-Rhin-2008) sur des paléochenaux d'une rivière du piémont des Vosges en Alsace, le Giessen, et une ancienne mare artificielle antique apportent un éclairage sur la formation et l'évolution de cet espace au cours de l'Holocène. L'approche a été établie à partir de l'observation morphostratigraphique des terrains et par l'intermédiaire d'analyses sédimentologiques, chronostratigraphiques et palynologiques. A l'Holocène ancien et moyen, la zone d'observation est traversée par trois chenaux : ils sont respectivement datés du Boréal (10200-8900 cal. BP) / Atlantique ancien (8900-6800 cal. BP), de l'Atlantique récent (6800-5700 cal. BP) et du Subboréal (5700-2600 cal. BP). Leur tracé migre peu à peu vers le nord en direction du cours actuel de la rivière. La présence d'une mare artificielle gallo-romaine, autour de laquelle s'est développée une activité agropastorale, a permis l'enregistrement et l'analyse des séquences de l'Holocène récent. Au I I I e siècle ap. J.-C., la plaine alluviale alterne entre secteurs humides et espaces plus secs. Aucun dépôt d'inondation du Giessen n'est enregistré sur la zone d'étude. A partir du I V e siècle ap. J.-C., l'habitat gallo-romain s'éloigne de la mare qui s'assèche probablement sous l'effet d'une baisse du niveau piézométrique de la nappe phréatique. A partir du V I I I e siècle ap. J.-C. jusqu'aux périodes contemporaines, la zone d'étude est recouverte par des dépôts de débordements du Giessen. La variété des faciès souligne le large potentiel de mobilité de la rivière. A cette augmentation des dépôts sont associées les traces d'un déboisement constant.

The decade of excavations on the Hexenberg site led to a first archaeological synthesis. An important research problem concerns the relationship between the site, the floodplain (here, the North Ried) and the former course of the Rhine (now the Hexenberg is situated in the agricultural plain, at five kilometers from channelized river). To answer this issue, a study window was opened between Seltz and Drusenheim from the review of a LIDAR document, old maps, aerial photos and results from two recent operations in preventive archaeology to understand its relationships with its environment. A palaeochannel a hundred meters wide is still marked in the landscape and spends about five hundred meters down the Hexenberg hill. It seems to connect to the Rhine system and recent observations show a contemporary hydrological activity of the Hexenberg occupation. In addition, studies on metal objects rejected in ancient branches of the Rhine confirm this dating. The river has moved from west to east since the Protohistory. However, these data are fragile and this study marks the beginning of an extensive recognition and dating of Rhine paleobranches. The archaeological site, fortified by a palisade, is occupied during a relatively brief period, the late Bronze Age, with no prior occupation. The site was deserted, and although “ cleaned” during the Hallstatt C, and was briefly reoccupied by a small Gallo-Roman necropolis and a moat of the Early Middle Ages. The 4,000 m2 excavated revealed 197 structures and 100 stratigraphic units, making it a densely occupied site in comparison with the other known sites of the Rhine plain where the loess substrate, subjected to the agricultural erosion, are troncated to several tens of centimeters. The main strucutures are mainly shallow structures, similar to storage spaces. There are some silos (twenty cases) and, in e qual proportion, a serie of pits associated with undetermined bilobed skills. There is no pole building. The archaeological material consists of 900 kg of sherds within which 881 vases were isolated. In this group, we can find a wide variability of types especially for the open forms. The printed decorations on the high forms are varied. The decoration of red and polychrome paint is also present, but this corpus is very fragmented. Besides the pottery, we should report the presence of several fragments of clay crescents and ridge tiles, spindle whorls, cheese presses and loomweights. Metal artifacts, according to the habitat, differs by the presence of two main tools (burin and chisels). The study of lithic industry and petrographic determination attest the presence of a wide variety of raw materials, not yet certified in the Alsatian sites of this period (brecciated sandstone, basalt). The faunal spectrum indicates a preference for beef, wild animals and pork. These studies allow a better characterization of the Hexenberg site and its location, in relation with the course of the Rhine. This occupation appears as an original site in the Alsace plain during the final phase of the Bronze Age.

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