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Seminar Details

Marine reptile on the Tethys Sea margins (southern Negev, Israel) and its palaeogeographic reconstruction

Date

10/03/2016

Lecturers

Dr. Rivka Rabinovich - Institute of Earth Sciences, Institute of Archaeology, National Natural History Collections, Hebrew University of Jerusalem

Abstract

Recent research on the late Cretaceous (Santonian), Menuha Formation of the southern Negev, Israel, has revealed several unconformities in its exposures, spatial changes in its lithofacies, agglomerations of its carbonate concretions and nodules at a variety of localities. At Menuha Ridge Site 20, portions of a new elasmosaurid skeleton were found within deposits of laminated bio-micritic muddy limestone with thin phosphatic layers. The sediments are rich in microfossils – foraminifera and ostracods preserved in the carbonate mud. Planktic foraminifera species (e.g. Dicarinella asymetrica, D. concavata, Sigalia decoratissima carpatica) appear as well as species indicative of opportunistic life strategies typical of a forming upwelling system in the region. Marine ostracods (e.g. Brachycythere angulata, Cythereis rosenfeldi evoluta) and many echinoid spines suggest an open marine environment. Using a multidisciplinary approach, we offer here a reconstruction of the micro-regional palaeogeography along a segment of the ancient shoreline of the Tethys Sea during the Santonian, and explain the environmental conditions under which the various fauna lived. This new elasmosaurid is examined in light of the above and compared with evidence from the adjacent areas along the margins of the southern Tethys Sea. The phosphatic belt is dated later than the Santonian in most localities, but the beginning of the unique condition that led to its deposition probably started at the beginning of the Santonian. Thus, our study offers additional evidence of finds available along the eastern exposure of the Mediterranean Tethys where elasmosaur remains have been found together with those of various fish. They appear in an environment of increased surface water productivity and decreased sea floor aeration, one that presages the onset of the upwelling regime in the late Santonian of our southern Levant.

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