Radiometric dating of hillslope calcrete in the Negev Desert, Israel

Abstract

The radiometric dating of calcrete is often problematical because impurities and open system conditions affect the apparent ages obtained. By applying both radiocarbon and uranium-series dating to calcrete in colluvium, it is shown that such conditions can be identified. In correlation with the stratigraphy, it is found that partial recrystallization severely decreases the radiocarbon ages of the upslope and shallower samples further down, whereas incorporation of limestone fragments from bedrock significantly increases the apparent ages of some of the uranium-series samples. It is concluded that the hillslope calcrete at the study site near Sede Beker in the Negev Desert, Israel, mainly developed shortly after 40 kyr ago, at a time when the Jordan Valley was being inundated to form the fossil Lake Lisan. Since their formation would have required higher rainfall than today, the results provide further evidence that the whole region was experiencing an increase in precipitation.

A conceptual model of multi-scale formation processes of open-air Middle Paleolithic sites in the arid Negev desert, Israel

“…Simultaneously, fluvial, aeolian, weathering, and soil-formation processes were active and shaped the present-day landscape. These include bedrock weathering (Yair, 1983; Wieler et al, 2021), cycles of loess deposition, erosion and redeposition, differential slope runoff generation (Wieler et al, 2016), fluvial incision and deposition, calcrete formation (Vogel and Geyh, 2008) and the formation of Reg soils through incorporation of dust and salt into the clastic sediments, clast shattering, and surface patination. Several fluvial terraces, dated to the last 0.5 Ma, have developed as a result of incision and episodic deposition of fluvial sediments, mainly controlled by climatic fluctuations (Goldberg, 1976, 1986; Porat et al, 2010; Matmon et al, 2016; Avni et al, 2017, 2021).…”

7.34 Hillslope Processes in Arid Environments

“…Near the Sede Boquer in the Negev, soil formation on the limestone bedrock produces horizons of pedogenic calcite (e.g., Vogel and Geyh, 2008). Near the Sede Boquer in the Negev, soil formation on the limestone bedrock produces horizons of pedogenic calcite (e.g., Vogel and Geyh, 2008).…”

“…On lowslope landforms, incomplete salt leaching distributes salts by solubility within soil profiles in the Negev (Amit et al, 2010), the Namib (Amit et al, 2010), and the Atacama (Ewing et al, 2006). Within hillslope soil profiles, salinity increases with increasing depth, and halite, gypsum, and pedogenic carbonate are distributed by solubility (Yair, 1990;Vogel and Geyh, 2008). In the Negev, soils are most saline toward the top of the hillslope and decrease in salinity toward the midslope as the volume of runoff increases (Yair, 1990).…”