Le système de terrasses fluviatiles et l’Acheuléen de la vallée de la Somme : séquences quaternaires et sites préhistoriques de référence

Abstract

Beside to be a major place for prehistoric research since the mid-19th century, the Somme Valley has also played a major role in the history of Quaternary geology. It has been the subject of numerous studies that have revealed a system of ten fossil alluvial terrace formations indexed from I to X, stepped between +5 and +55 m relative altitude in relation to the maximum incision of the current valley into the bedrock, whose fluvial deposits are covered by sequences up to 10 m thick, displaying alternatively loess and paleosol levels. The combined and multidisciplinary study of these terrace deposits has made it possible to construct one of the world's best-established geological, chronological, and paleoenvironmental frameworks for the last million years. In the present paper, after summarizing the different stages of formation of the terrace system in relation to the major Pleistocene climate cycles, the main data obtained on the formations that yielded Acheulean industries will be briefly presented. These formations are mainly the Renancourt Sheet (Alluvial Formation VII of the Somme terraces system, MIS 16-15), which yielded the oldest archaeological traces currently attested in Northern France at Moulin Quignon and Carpentier Quarry, the Garenne Sheet (Alluvial Formation V, MIS 12-11), which is associated in particular with the eponymous site of Saint-Acheul and the deposits of Cagny-la-Garenne, and the Épinette Sheet (Alluvial Formation IV, MIS 10-9), which recorded the last Acheulean evidence in the valley and the transition to the Middle Paleolithic.