Late Glacial and Holocene development of semi-closed depressions (thaw lakes?) in the Limagne Rift Valley, French Central Massif

Abstract

Palynological, micromorphological, tephrochronological and sedimentological studies of the deposits in semi-closed depressions in the Limagne Rift Valley in France testify to development in five stages: (1) an erosional, probably interglacial stage, with differential fluvial erosion of soft Oligocene marls not protected by overlying terrace gravels; (2) a fluvial-periglacial stage, with deposition of fluvio-periglacial sediments, partly involuted subsequently; (3) a lacustrine stage, possibly related to thermokarst, with deposition of calcareous mud and volcanic ash layers in the Late Glacial; (4) peat growth and deposition of black clays in the Preboreal, Boreal and Atlantic, and (5), depending upon local conditions, fluvial deposition, soil formation, or lacustrine deposition until recent times.