T97 Cenozoic Paleoclimates and Ecosystems I

Monday, 23 October 2017
8:00 AM - 12:00 PM
Room 609

ESR DATED STRATIGRAPHIC SEQUENCES AT BIR TARFAWI (SOUTHERN EGYPT): PLEISTOCENE ARCHAEOLOGICAL AND PALEONTOLOGICAL OCCURRENCES ASSOCIATED WITH WET CLIMATE CONDITIONS DURING ISOTOPE STAGES 7 AND 5

Paper number: T97-9
Program: Technical Sessions
Time: 10:00 AM – 10:15 AM

Authors

Abstract

Bir Tarfawi is a small uninhabited oasis in Egypt's hyperarid Western Desert. Although groundwater lies near the surface in the southern area, Quaternary fossils and artifacts are asociated with stratigraphic sequences consisting of carbonate marls, as well as palustrine and lacustrine silts and sands intercalated with aeolian sediment. The sedimentary deposits demonstrate that the region experienced alternating arid-wet-arid climatic cycles. During arid intervals, deflationary basins formed. Due to higher watertables in wetter periods, wetlands, marshs, ponds, and small lakes supported vertebrate and invertebrate communities. Pleistocene hominins left behind their Acheulean and Middle Paleolithic/Middle Stone Age (MP/MSA) Nubian Complex artefacts in marginal lacustrine or palustrine deposits. Stratigraphically associated with MP/MSA artefacts, Melanoides tuberculata shells were collected from the White Lake Basin (WLB) and Locality E-86-2 for ESR dating. In the central WLB, ~ 2 m of carbonate-rich sediment was deposited in deeper water. At the WLB edge, higher clastic concentrations reflect a shallow marginal habitat. With two mollusc ESR dates averaging 236 ± 19 ka assuming linear uptake (LU), the WLB waterbody likely existed during Marine (Oxygen) Isotope Stage (MIS) 7e. In another more southerly deflationary basin, excavations near E-86-2 and E-86-3 revealed sediment from two wet climatic episodes. At E-86-2, basal and hydromorphic sands underlie more calcareous sediment deposited in a near-shore basin edge facies during a wetter transgressive phase. The weighted mean age, 81.8 ± 4.8 ka (LU), for two mollusc ESR samples collected at E-86-2 indicates that these molluscs correlate with MIS 5a, suggesting that higher watertables occurred then. Therefore, at Bir Tarfawi, higher watertables fed waterbodies during both MIS 5 and 7. Ages for the wetter phases at Bir Tarfawi also agree well with those seen at Djara Cave, Dakhleh and Kharga Oases, hinting that these wetter environments across the Western Desert permitted hominins migrate into and inhabit the driest parts of the Sahara, which was precluded during the drier periods.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-299240

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