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Spatially variable sedimentary responses to orbitally driven pluvial climate during Marine Oxygen Isotope Stage 5.1, Dakhla Oasis region, Egypt

Published online by Cambridge University Press:  20 January 2017

Ian A. Brookes
Ian A. Brookes*
Affiliation:
Geography Department, York University, Toronto, Ontario, Canada M3J 1P3
*
*1102-2 Mowat Avenue, Kingston, Ontario, Canada K7M 1K1. E-mail address: ibrookes@yorku.ca
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Abstract

Pleistocene basinal sediments (PBS) in the Dakhla region of Egypt's hyperarid Western Desert comprise four facies: (A) fluvio-lacustrine, (B) mixed lacustrine/pluvio-eolian, (C) pluvio-eolian, and (D) mixed eolian/pluvio-eolian. Contiguity of basins containing each facies, and their stratigraphic position between two bajada gravel formations, P/B-II and P/B-III, confirm their equivalence. Facies A and B, with lacustrine components, are attributed to orbitally forced poleward incursion of the Intertropical Convergence Zone (ITCZ), resulting in increased summer insolation/temperature/precipitation. Facies C and D, comprising pluvio-eolian and eolian sediments, reflect geologic/topographic influences overprinted on regional 'pluvial' conditions, eliminating lacustrine response. A Th/U age of ∼ 62 ka on lacustrine marl within Facies B is minimal, and an OSL age of 110 ± 18 ka on sediments immediately below Facies B is maximal. Since bajada gravels P/B-III are the youngest Pleistocene formation, they must represent the final strong incursion of the ITCZ into the Dakhla region at MIS 5.1, ∼ 80 ka. Because PBS Facies A pass rapidly up into P/B-III bajada gravels, PBS are assigned to the rising limb of the MIS 5.1 insolation/temperature/precipitation curve, slightly younger than 80 ka.

Keywords

EgyptPleistoceneMarine Isotope Stage 5SedimentologyStratigraphy
Type
Research Article
Information
Quaternary Research , Volume 74 , Issue 2 , September 2010 , pp. 252 - 264
Copyright
University of Washington

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