Pliocene-Pleistocene palaeoclimate reconstruction from Ashalim Cave speleothems, Negev Desert, Israel

Speleothems from Ashalim Cave, located in the arid central Negev Desert, Israel, were used in a reconstruction of the palaeoclimate of the northern Saharan-Arabian desert margin. The sequence of speleothems is composed of three stratigraphic members: the yellow Pliocene Basal Member, the brown Early Pleistocene Intermediate Member and the thin Middle-Late Pleistocene Young Member. The age of the Basal Member is c. 3.1 Ma and the base of the Intermediate Member is 1.272 ± 0.018 Ma. Two last deposition periods of the Young Member occurred at 221-190 ka (Negev Humid Period (NHP) 2) and 134-114 ka (NHP-1), associated with interglacial marine isotopic stages 7.3-7.1 and 5.5, respectively. NHP-1 and -2 occurred when the African monsoon index was highest in the last 221 ka. The δ18O values of the speleothems range between −6.9 and −11.2‰, 2-4‰ less than in the speleothems of central and northern Israel. This may indicate a remote southern tropical source of precipitation, although during NHP-1 and -2 the thickness of the Negev Desert speleothems decreases from north to south, showing a stronger northern Mediterranean source of moisture. The δ13C values of the speleothems (3.5 to −8.5‰) show steppe to semi-desert C4 type vegetation. The 87Sr/86Sr ratios of the speleothems increased from c. 0.7078 in the Pliocene to 0.7082-0.7085 in the Pleistocene, indicating an increasing supply of desert dust and a decrease in host rock weathering.