Integrated multi-site U–Th chronology of the last glacial Lake Lisan

Abstract

We present a new integrated multi-site chronology for Lake Lisan, which occupied the Dead Sea basin and Jordan Valley during the last glacial period (70–14kka, Marine Isotope Stages 4,3,2). The Dead Sea basin lacustrine deposits are unique among closed basin sediments in that they formed in a deep, hypersaline water body that precipitated primary aragonite which is amenable to radiometric dating by U-series, providing a solid basis for studies of the relationship of Middle East climate to other changes in the high latitudes or the tropics.The application of U–Th dating for lacustrine carbonates requires corrections for detrital U and Th and hydrogenous (“initial”) 230Th. Here we followed an iterative approach, in which we evaluate the composition of the detrital contamination independently for every set of coeval samples to determine the corrected ages. These were further filtered and combined with lithological–limnological considerations, which were used to construct age–height models for all studied stratigraphic sections. Finally, the ages of stratigraphic tie-points were used to integrate the individual age–height models into a unified chronology. The resulting chronological framework indicates that the ages of several primary gypsum units associated with catastrophic lake level drops correspond with the timing of Heinrich events in the North Atlantic. Thus, a final iterative step involves refining the ages of “Lisan-gypsum events” based on the ages of Heinrich events 6, 5, 5a, 4, and 1. This approach yields an unprecedented basin-wide, unified, event-anchored chronology for the Lisan Formation, with typical age uncertainties ca. 1000–2000years (95% confidence limit) across the entire last glacial, well below those typically related to individual U–Th and radiocarbon dating of “dirty” carbonates from similar time intervals. The results can be further extrapolated to new sites and serve as a geochronometric reference for the reconstruction of the limnological history of Lake Lisan.