The Moselle piracy: new chronological data from U/Th dating of speleothems

The Moselle piracy is one of the most important changes of the hydrographic network in Lorraine (France). For a long time, this phenomenon has been presumed to be relatively recent (at the end of the Middle Pleistocene) because of the well-preserved fluvial morphologies and deposits. With new relations between the surficial and subterranean data in the piracy area, the capture has been dated from 300ka using U/Th method on speleothem. This evaluation reveals an earlier time for the phenomenon, and is more precise than those proposed up to now. The latter were derived from the North-European glacial chronology and one thermoluminescence date obtained in the downstream valley of Meuse. In fact, the improvements in absolute dating, thanks to different methods and U/Th in particular, lead geomorphologists to abandon the simple relation between the glacial-interglacial periods and the accumulation-erosion processes in rivers.