2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 8
Presentation Time: 3:15 PM

ESR Analyses for Herbivore Teeth from Dakhleh Oasis, Egypt: Constraining Pluvial Events in the Western Desert

BLACKWELL, Bonnie A.B., Department of Chemistry, Williams College, Williams College, Williamstown, MA 01267, LONG, Rebecca A., RFK Science Research Institute, Glenwood Landing, NY 11547-0866, KLEINDIENST, Maxine R., Department of Anthropology, University of Toronto, 3359 Mississauga Road North, Mississauga, ON L5L 1C6, Canada, CHURCHER, Charles S., Department of Zoology, University of Toronto, Toronto, ON M5S 3G5, Canada, SMITH, Jennifer R., Earth & Planetary Sciences, Washington University, 1 Brookings Dr, Campus Box 1169, St Louis, MO 63130, BLICKSTEIN, Joel I.B., RFK Sci Rsch Institute, 7540 Parsons Bvd, Flushing, NY 11366, SKINNER, Anne R., Department of Chemistry, Williams College, Williamstown, MA 01267-2692, KIENIEWICZ, Johanna, Department of Geosciences, Denison University, Granville, OH 43023 and ADELSBERGER, Katherine A., Earth and Planetary Sciences, Washington University in St. Louis, Campus Box 1169, One Brookings Dr, St. Louis, MO 63130, iloveamerica_528@yahoo.com

Dakhleh Oasis sits in the hyperarid Western Desert which today lacks naturally occurring surface water and receives 0.07 mm/y of precipitation. Paleolithic artefacts, fossil ungulate teeth and snails that dot its Pleistocene deposits and surface record a time when surface water did exist in small ponds and lakes for hominids to drink, thanks to higher rainfall during pluvial events. Pleistocene artesian spring deposits, buried soils, and lake sediment all demonstrate that the Oasis had surface water during at least three pluvials. The lakes deposited calcerous silty sediment (CSS), which also houses the Dakhleh impact glass (DG). Differential GPS measurements show a paleolake with an area of about 60 km2 during the late Middle Pleistocene.

Electron spin resonance (ESR) can date tooth enamel ranging from 5 ka to 5 Ma in age. From Dakhleh's Localities D006 and 348, 17 herbivore tooth fragments were dated with ESR. At 348, the CSS marls yielded Pleistocene bone fragments, MSA artefacts, snails, marsh grass macrofossils and stem casts, Alcelaphus, zebra, pig, and freshwater snails. At D006, sand dunes, deflation, and blowouts complicate the stratigraphy. The mid-Holocene lake deposits forms most of the surface, but blowouts expose red CSS mud. Several different layers were deflated onto the surface lag. Blowouts yielded Middle Pleistocene skeletal remains from Gazella, Phacochoerus, Loxodonta africana, Hippopotamus, Pelorovis antiquus, and Felis lybica. Although better cosmic dose rate modeling would improve their accuracy, the preliminary ESR ages indicate that mammals lived at Dakhleh during three periods. Teeth dated at 58 ± 5 ka, correlating with early Oxygen Isotope Stage (OIS) 3, 109-111 ± 10 ka (OIS 5c), 127-130 ± 15 ka (OIS 5e), and 159-184 ± 15 ka (OIS 6c). The herbivore frequency data, therefore, indicate that at least four pluvials made the Western Desert more habitable during the late Pleistocene.