Palaeosols and late Pleistocene rainfall fluctuations in the Negev Desert

Abstract

The existence of a series of palaeosols in the present-day desert region of southern Israel (the northern Negev Desert)^1,2 indicates recurring periods of wetter climate in the past. Up to seven well-developed palaeosols occur within a section and each has a horizon containing soft calcium carbonate nodules (3–15 mm in diameter). The palaeosols are developed within loess or fluvially redeposited loess consisting of silty clay or clayey silt. The ¹⁴C ages of the uppermost three calcic horizons average ∼ 13,000 yr BP (calcic horizon, CH-I), ∼28,000 yr BP (CH-II), and ∼37,000 yr BP (CH-III). Drier phases occurred between these periods of pedogenesis, especially during the last glacial maximum (centred at ∼18,000 yr BP), when extensive erosion occurred. Analysis of the ¹³C content of nodule carbonates points to the occurrence of strong north-south rainfall gradients during each period of calcic horizon formation, which excludes the possibility of monsoonal rains contributing to the increased rainfall during these periods. The palaeosols correspond to global warm phases of the last glacial period.