Ghar Alisadr, Hamadan, Iran: Dating of Calcite Shelfstones
|Institut für geologische Wissenschaften, FU Berlin, Germany|
|Geological Survey of Iran, Tehran, Iran.|
|Iran; Caves; Palaeo-climate; Speleothems; Ice ages|
Several fossil calcite shelfstones above the present water table in Ghar Alisadr (Alisadr cave), Iran, indicate a more humid climatic episode. Climatic conditions must have at least provided 600~mm/yr paleo-recharge, which is twice the amount the region receives today. The location of the calcite shelfstones above the water table can be explained, if the aquifer has a fairly low transmissivity, which is untypical for mature karst aquifers. The cave-bearing limestone layer therefore seems to be thin and is partially blocked towards the resurgences, otherwise an increase of more than two meters in water table cannot be satisfactorily explained. In this project, samples from different calcitic ledges are taken, both in Ghar Alisadr and from other caves in vicinity. The age of the samples will be determined by the U/Th-method, and results are compared to other oceanic and continental records of palaeo-climate variability in the region.