(230)Th/(234)U Dating of the Quaternary Spring Travertines in the Arava Rift Valley of Israel and Paleoclimatic Implications. Final Report for the Period 15 December 1986 - 15 December 1987.

摘要

Springs and lake deposits (travertines) sampled along the western margins of the Arava segment of the Dead Sea Rift Valley, Israel, were studied as a potential source of palaeoclimatic information. The (230)Th/(234)U disequilibrium method was used to determine the age of the investigated deposits. The radiometric dating was supplemented by detailed petrographic and chemical analyses of the collected samples. Detailed petrographic observations of the analysed travertine samples suggest their deposition under moderately-arid conditions, alternating with arid to extremely arid periods. This evidence is consistent with the preliminary conclusions drawn from palynological studies in the area. Dating by the (230)Th/(234)U disequilibrium method indicates that most travertine ages correspond to oceanic (18)O stages 5 and 7. The good correspondence between apparent ages as deduced from the position of the travertines in vertical and lateral successions and the radiometric ages, lends credibility to the radiometric ages. The clustering of ages during the warm /sup 18/O stages bears similarity to the temporal distribution of middle to late Pleistocene sapropelic horizons in the Eastern Mediterranean Basin which further leads to suspicion that during insolation maxima monsoonal cells originating in the Indian Ocean have shifted northwards reaching the latitude of the Arava and Negev Highlands. Refs and figs. (Atomindex citation 20:048026)