Données nouvelles sur la dynamique fluviale postglaciaire et la sédimentation des fonds de vallée en Bretagne. Le cas de la vallée du Steïr près de Quimper (Finistère, France)

Abstract

The building of the road to bypass of the town of Quimper (Finistère, Brittany) has allowed the discovery of a La Tene human settlement in the floodplain of the Steïr river valley upstream of Quimper at Kergolvez. Archeological works were realised in 2004 and 2005, on approximately 3 ha. Thanks to three long perpendicular excavations, the detailed archeological and geomorphological observations allows to understand the environmental context of the settlement and its later abandonment, a craft and trade agglomeration lived between the end of the third or the beginning the second century BC and the middle of the second part of the first century BC. The excavations show a thickness of 2 to 3 m of gravels, sands and fine particles which correspond to a part of the floodplain sedimentation during the Tardiglaciaire and Holocene. They also reveal the paleo-channel of a abandoned meander on the left bank of the river. On one hand, these observations allow to precise the post-glacial fluvial dynamics for the West of the Armorican peninsula. Links are also established with the Post-glacial fluvial dynamics of the northwest of France where the stages of the tardiglacial and Holocene valleys infillings are already specified. On the other hand, this kind of observations, that are still insufficient at the regional scale, provides some additional knowledge about the regional sedimentary transfers from the mainland to the coastal areas over the Holocene periods.

Keywords

• Holocene
• sedimentation
• valley floor
• river dynamic
• Tardiglacial
• La Tene period