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Relating eolian bounding-surface geometries to the bed forms that generated them; Etjo Formation, Cretaceous, Namibia

Nigel Mountney, John Howell, Stephen Flint and Dougal Jerram
Relating eolian bounding-surface geometries to the bed forms that generated them; Etjo Formation, Cretaceous, Namibia
Geology (Boulder) (February 1999) 27 (2): 159-162

Abstract

The Cretaceous Etjo Formation is a 200-m-thick eolian and fluvial sandstone succession exposed in the Huab Basin of northwestern Namibia. Eolian sedimentation was terminated abruptly by the emplacement of flood basalts of the Etendeka igneous province across much of the basin at 132+ or -1 Ma. The lavas "drowned" the dunes and, in doing so, preserved bed forms with heights and wavelengths of up to 100 m and 1.3 km, respectively. Subsequent erosion has resulted in the exposure of these bed forms and provides a rare opportunity to accurately reconstruct the three-dimensional geometry of an ancient eolian system and to relate bed-form morphology to bounding-surface geometries. Some bed forms lacked a single active slipface but instead were characterized by a dome form over which smaller transverse dunes migrated. Other bed forms were characterized by an active slipface and a stoss slope over which smaller, superimposed bed forms migrated. One bed form records a transitional evolution between these two end-member types. Preserved bed sets exhibit a positive (but stoss-erosional) angle of downwind bed-form climb of 1 degrees . Bed forms of the Etjo Formation provide an opportunity to directly relate bed-set thickness to original bed-form height via the angle of climb.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 27
Serial Issue: 2
Title: Relating eolian bounding-surface geometries to the bed forms that generated them; Etjo Formation, Cretaceous, Namibia
Affiliation: University of Liverpool, Stratigraphy Group, Liverpool, United Kingdom
Pages: 159-162
Published: 199902
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 23
Accession Number: 1999-021267
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., sketch map
S20°30'00" - S20°15'00", E13°40'00" - E14°10'00"
Secondary Affiliation: Universitaet Wuerzburg, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199908
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