PLIO-PLEISTOCENE PALEOENVIRONMENTS IN THE NORTHWESTERN NEGEV, ISRAEL: INSIGHTS FROM TEL SHARUHEN- BESOR VALLEY

The 50 m thick Plio-Pleistocene sequence exposed at Tel Sheruhen, which is located on the left bank of the Besor river, northwestern Negev, is composed of bedded eolian and fluvial sand units that were episodically exposed to pedogenesis. The characteristics of the sediments and the buried sandy calcic soils were influenced by the position of the southeastern Mediterranean coastline with respect to the study area. Paleomagnetism, indicative shallow marine fossils and luminescence dating methods indicate that this sequence was deposited between the late Pliocene and middle Pleistocene (340 ka), a time interval for which little information on the region exists. The paleoenvironment during this period was reconstructed using sedimentology analyses, soil stratigraphy, soil micromorphology, and d¹³C and d¹⁸O of soil carbonate nodules. The calcic soils indicate arid to semiarid climates, and the variations of d¹⁸O in the sequence point to abrupt and/or gradual transitions between these two climates. Soil macro- and micro- morphology demonstrate that vegetation cover was sparse and comprised mainly grasses and bushes. d¹³C values reveal a continuous synchronous existence of C₃ and C₄ vegetation in varying ratios. Inverse trends of light d¹⁸O versus heavy d¹³C values in the upper units are explained by increased water leaching through the sandy soil profile during more humid periods. Water percolation caused increased dissolution of inorganic carbonates from dust input, land snail shells and parent material, which contributed heavy d¹³C values to the pedogenic carbonates. The sparse vegetation, even in a more humid climate, is attributed to the instability of environments in this near-coast sandy area caused by a strong-wind regime. It is concluded that wind is more crucial than precipitation for stabilization of sandy areas by vegetation. Therefore, in windy environments, during moister periods, light d¹⁸O values together with heavy d¹³C values in soil carbonates are expected. Slightly more arid conditions, typified by heavier d¹⁸O but characterized by weaker winds and a more stable environment, will allow the development of soils with enhanced biogenic activity typified by lighter d¹³C values.