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Depositional environment and OSL chronology of the Homeb silt deposits, Kuiseb River, Namibia

Published online by Cambridge University Press:  20 January 2017

Pradeep Srivastava ,
George A. Brook ,
Eugene Marais ,
P. Morthekai  and
Ashok K. Singhvi
Pradeep Srivastava*
Affiliation:
Department of Geography, University of Georgia, Athens, GA 30602, USA
George A. Brook
Affiliation:
Department of Geography, University of Georgia, Athens, GA 30602, USA
Eugene Marais
Affiliation:
National Museum of Namibia, P.O. Box 1203, Windhoek, Namibia
P. Morthekai
Affiliation:
Physical Research Laboratory, Navrangpura, Ahmedabad 380009, India
Ashok K. Singhvi
Affiliation:
Physical Research Laboratory, Navrangpura, Ahmedabad 380009, India
*
*Corresponding author. Wadia institute of Himalayan Geology, 33 GMS Road, Dehradun-248001, India. E-mail address:[email protected] (P. Srivastava).
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Abstract

Previous studies suggest that the Homeb silts of the Kuiseb valley, Namibia (i) accumulated in a dune-dammed lake, (ii) are end-point deposits, (iii) represent an aggrading river bed, and (iv) are slackwater deposits. Thus, they have been used alternatively as evidence of past drier conditions or past wetter conditions. Lithostratigraphic analysis of two sediment sequences at Homeb indicates sedimentation by aggradation of the Kuiseb River triggered by a transition from an arid to humid climate. OSL ages for the sequences were obtained by the SAR protocol on aliquots of 9.6-mm and 4.0-mm diameter and on single grains. Four-millimeter aliquot minimum ages closely approximate the single-grain minimum ages and are younger than 9.6-mm aliquot minimum and central ages. Based on these results, the small-aliquot (4-mm) approach appears to provide ages comparable to those obtained by the more laborious and time-consuming single-grain method. Minimum ages indicate rapid deposition of the Homeb Silts in at least two episodes centered at ∼15 ka and ∼6 ka during climate transitions from arid to humid. Flash floods eroded the valley fills during slightly more arid conditions.

Keywords

Namib DesertHomeb SiltSedimentary environmentLuminescence dating
Type
Research Article
Information
Quaternary Research , Volume 65 , Issue 3 , May 2006 , pp. 478 - 491
Copyright
University of Washington

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