Paper No. 3
Presentation Time: 2:00 PM
ESR DATING QUATERNARY LACUSTRINE DEPOSITS AT DAKHLEH OASIS, EGYPT
BLACKWELL, Bonnie A.B., Department of Chemistry, Williams College, Williamstown, MA 01267,
DEELY, Aislinn E., RFK Science Research Institute, Glenwood Landing, NY 11547-0866, TRUONGCHAU, Thomas M., RFK Science Research Institute, Glenwood Landing, 11547-0866, KLEINDIENST, Maxine, Department of Anthropology, University of Toronto at Mississauga, 3359 Mississauga Road North, Mississauga, ON L5L 1C6, Canada, CHURCHER, Charles S., Department of Zoology, University of Toronto, Toronto, ON M5S 3G5, Canada, SKINNER, Anne R., Department of Chemistry, Williams College, Williamstown, MA 01267-2692, SMITH, Jennifer R., Earth & Planetary Sciences, Washington University, 1 Brookings Dr, Campus Box 1169, St Louis, MO 63130 and BLICKSTEIN, Joel, Box 866, RFK Science Research Institute, Glenwood Landing, 11547-0866, aislinndeely@yahoo.com
During the Pleistocene, Paleolithic hominids lived at Dakhleh Oasis, Egypt, a hyperarid area that today lacks any naturally occurring surface water. Ungulate fossil teeth and molluscs that occur in its Pleistocene lacustrine muds and deflated surfaces record a time when surface water did exist for these hominids to drink, thanks to higher rainfall during these pluvial events. Dating the teeth from the animals pinpoints the pluvial events that enabled hominins to inhabit this region. Located 150 km west of Kharga, and 350 km west of the Nile in the Western Desert, Dakhleh Oasis covers ~ 1200 km2. The oasis formed as a depression ablated by the wind. Cretaceous sandstone, limestone, and shale cover the Dakhleh basin. Lacustrine marls up to 8.0 m thick occur on the edges of the Kellis, Balat, and Tineida Basins. At Snail Hill (Locality 348), marly lake deposits ~ 5-6 m thick from the Lake Teneida Fm. (CSS) overlying a Cretaceous bedrock high have yielded Pleistocene ungulates, Aterian artefacts, freshwater molluscs, marsh grass macrofossils and stem casts. At Locality D006, blowouts have exposed the Pleistocene Lake Kellis Fm. which has yielded Middle Pleistocene ungulates. Electron spin resonance (ESR) can date vertebrate teeth ranging from 5 ka to 5 Ma in age, and snails, from 5 ka to 2 Ma, by calculating accumulated doses from radiation-sensitive ESR signals preserved in the minerals, and measuring the radiation dose rates in the fossils and their associated sediment. From Snail Hill, one tooth fragment gave a LU age of 184 ± 11 ka (Oxygen Isotope Stage, OIS 6d), which agrees well with dates for the overlying CSS at Snail Hill. At Locality D006, 21 analyses from on 16 tooth fragments yielded three groups of LU ages, ~ 60 ka (OIS 3), 110-130 ka (OIS 5d-5e), and 159-171 ka (OIS 6c-6d). These preliminary ESR analyses suggest that abundant water existed in Dakhleh, Egypt, during at least three different periods, suggesting that artefacts date from the same periods.
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