Abstract:
Mineralogical and sedimentological investigations were carried out on a karst filling located in the Cotencher cave (Neuchatel, Jura mountains, Switzerland). Radiometric and archeological dating give evidence for a rather incomplete record of the climatic history of the last glacial period. The major hiatus is situated in the younger Wurmian Pleniglacial age. Following the mineralogical and sedimentological results, it is possible to divide this profile in three parts. Late glacial and holocene sediments are characterized by fine morainic material, redeposited due to karst activity. The middle part (C-14: > 40 Ky BP), directly located below this hiatus shows a typical mineralogical association with the appearance of kaolinite and the persistance of the amphibole. This association is thought to be of eolian origin, older than the one described on the Jura mountains actual soils. This eolian sediment component was deposited after the early Wurmian Pleniglacial period. on the soils in the vicinity of the cave, and resedimented into the cave during the Wurmian Interpleniglacial. The lower part of the sediment column is characterized by a mineralogical association of kaolinite, mixed-layers and mica. Especially high amounts of kaolinite, possibly derived from old, probably Eemian mature soils give evidence for relatively warm climate with strong seasonal variations