HR: 1340h
AN: U13B-1156    [Abstracts]
TI: Combined U-decay Series and Oxygen Isotope Dating of a Mid-Pleistocene Lacustrine Sequence: The Amora Formation, Dead Sea Basin, Israel
AU: * Torfstein, A
EM: adi.torf@mail.huji.ac.il
AF: Institute of Earth Sciences, The Hebrew University of Jerusalem, Giva'at-Ram Campus, Jerusalem, 91904, Israel
AU: * Torfstein, A
EM: adi.torf@mail.huji.ac.il
AF: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel
AU: Haase-Schramm, A
EM: Alexandra.Haase-Schramm@oxinst.com
AF: Max-Planck Institut fu¨r Chemie, Postfach 3060, Mainz, D55020, Germany
AU: Haase-Schramm, A
EM: Alexandra.Haase-Schramm@oxinst.com
AF: GEOMAR, Forschungszentrum fu¨r marine Geowissenschaften, Duesternbrooker Weg 20, Kiel, D-24148, Germany
AU: Waldmann, N
EM: nicolas.waldmann@terre.unige.ch
AF: Institute of Earth Sciences, The Hebrew University of Jerusalem, Giva'at-Ram Campus, Jerusalem, 91904, Israel
AU: Waldmann, N
EM: nicolas.waldmann@terre.unige.ch
AF: Department of Geology and Paleontology, University of Geneva, 10, route de Suisse, Versoix, 1290, Switzerland
AU: Kolodny, Y
EM: Kolodny@vms.huji.ac.il
AF: Institute of Earth Sciences, The Hebrew University of Jerusalem, Giva'at-Ram Campus, Jerusalem, 91904, Israel
AU: Stein, M
EM: motis@vms.huji.ac.il
AF: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel
AB: Dating of mid-Pleistocene carbonate sediments is challenged by the lack of suitable absolute radiometric methods. Here, we present a combined approach that utilized the U and Th isotopes with floating δ¹⁸O stratigraphy and paleomagnetic constraints, and established a high-resolution chronology of the mid to upper Pleistocene Lake Amora in the Dead Sea basin. The application of the δ¹⁸O record as a floating chronometer is based on the correlation found between δ¹⁸O values of synchronously deposited upper-Pleistocene and Holocene lake sediments, East Mediterranean foraminifers and Judean Mountains speleothems (Kolodny et al., 2005). The lacustrine Amora Formation consists of laminated aragonite and detritus, Ca-sulfate minerals, halite and clastic units. The sediments were depsoited in the lacustrine environment of the paleo-Dead Sea basin and were later uplifted and tilted by the rising Sedom diapir, exposing ~330 m of the formation on the eastern flanks of Mt. Sedom. δ¹⁸O values range between 6.0 and –1.0‰, shifting periodically between glacial and interglacial sequences throughout the sedimentary section, marking corresponding shifts in the global marine records. Paleomagnetic data indicate the entire section was deposited after the 780 ka Matuyama-Brunhes magnetic transition. Data compilation renders the age of the base of the exposed Amora Fm. to be ~750 to 700 ka BP (MIS 18 to 17), and the age of its capping sediments to be between ~200 and 130 ka BP (MIS 6 and the transition to MIS 5). Climatic-limnologic shifts throughout the sedimentation period are recorded by the lithological, chemical and isotopical properties of the sediments, and are correlated to global and regional events. A prominent ~6 meter thick salt layer precipitated during MIS 11 (~400 ka BP) and marks a significant lake level decline. The only other time a similar salt unit precipitated from the Dead Sea basin lakes during last ~750 ka, was before ~10 ka (Pleistocene-Holocene transition). The striking similarity between the MIS11 and Holocene sedimentary records supports the assumption that the lacustrine deposits reflect trends in in global climatic changes. Reference Kolodny Y., Stein M., and Machlus M. (2005) Geochim. Cosmochim. Acta 69, 4045-4060.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1105 Quaternary geochronology
DE: 1115 Radioisotope geochronology
DE: 4239 Limnology (0458, 1845, 4942)
SC: Union [U]
MN: 2007 Fall Meeting