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Late Holocene Paleoseismic record recovered from the Dead Sea deposits Revital Bookman (Ken-Tor) PhD thesis with: Mordechai Stein, The Geological Survey of Israel Amotz Agnon and Yehuda Enzel, Institute of Earth Sciences, Hebrew University, Jerusalem
Shmuel Marco
Department of Geophysics and Planetary
Sciences
Publications: 1. Ken-Tor, R., Agnon, A., Enzel, Y., Marco, S., Negendank, J. F. W., and Stein, M., 2001. High-resolution geological record of historic earthquakes in the Dead Sea basin. J. Geophys. Res., 106: 2221-2234. (pdf file) 2. Ken-Tor, R., Stein, M., Enzel, Y., Agnon, A., Marco, S., and Negendank, J. F. W., 2001. Precision of calibrated radiocarbon ages of historic earthquakes in the Dead Sea Basin. Radiocarbon, 43: 1371-1382. Abstract The Dead Sea is a terminal lake located in a deep tectonic depression along the Dead Sea Transform. The sedimentary fill deposited in the basin recorded in detail its geological history. The drastic modern lake-level drop in the last decades exposed the Holocene sediments along the Dead Sea shores in incised gullies and fan deltas. This thesis studied the geological record of the Dead Sea basin during late Holocene from the exposed sequences. The research focused on the reconstruction of the paleoseismic and lake-level records described from the lacustrine deposits of the basin. Radiocarbon dating of organic debris from the sediments established the chronology of the records presented. The paleoseismic study records the appearance of seismites in the late Holocene lacustrine sediments documented from sequences in incised gullies at the Ze'elim plain, their dating, and correlation with historically documented earthquakes in the area. Eight seismites were correlated with the historical earthquakes of 64 and 31 BC and 33, 363, 1212, 1293, 1834 and 1927 AD. A few of the historical earthquakes that damaged the Dead Sea area have no correlatives in the Ze’elim seismite record due to erosion during low lake levels that exposed the sedimentary sequences to erosion (e.g., the 749 AD earthquake). Based on modern analogues and the association of similar disturbed layers with syndepositional faults, the Ze’elim seismites indicate M>5.5 earthquakes. The average recurrence interval is estimated as ~100-300 years and represents slip events on different faults in the Dead Sea area. Based on the identification of seismites as historical earthquakes we evaluated the precision of the radiocarbon ages of the seismites. The radiocarbon ages of samples collected from seismites were refined by applying stratigraphic constaints and tuning their calibrated calendar ranges to the known historical earthquakes. Most of the earthquakes fall well within the 1s standard deviation envelope of the calendar range. This refinement demonstrates that the lag period due to transport and deposition of vegetation debris is very short in this arid environment, probably not more than a few centuries and sometimes less than a few decades. This assessment of the seismite radiocarbon ages attests to the validity of radiocarbon ages in Holocene sediments of the arid area of the Dead Sea and demonstrates the ability to achieve highly precise radiocarbon ages.
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