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Mesozoic fluvial deposits on a rifted continental margin near Vaalputs, Namaqualand, South Africa

D. Brandt, M. A. G. Andreoli and T. S. McCarthy
Mesozoic fluvial deposits on a rifted continental margin near Vaalputs, Namaqualand, South Africa
South African Journal of Geology (March 2003) 106 (1): 11-16

Abstract

Scattered outcrops of faulted, silicified and kaolinitised (saprolitised) sediments comprising conglomerate and crossbedded sandstone, form prominent mesas and inliers near Banke, south of Vaalputs, the national radioactive waste disposal site in Namaqualand. Although their geomorphologic expression is similar, these sediments are lithologically and texturally distinct from the equally silicified soils, diatreme infills and hillside screes of the palaeo-weathering profile type commonly occurring between the farm Banke and the Vaalputs site. Sedimentary and structural features identified in this study show that the Dasdap sediments may represent an alluvial fan sequence with a source area in the west, and deposited on a continental margin marked by relatively steep topographic gradients. The Dasdap beds could not be dated conclusively, but there is evidence their deposition was likely coeval with the emplacement of melilititic and kimberlitic diatremes in the Late Cretaceous. The robust fluvial system inferred by the Dasdap sediments is compatible with the humid climate responsible for the siliceous saprolites widely associated to the erosional African surface across southern Africa. Subsequent to these events, widespread faulting and jointing of the sediments provide striking evidence for tectonic reactivation of the continental margin of southwestern Africa in the Cenozoic. On the basis of these distinguishing features, the Dasdap sediments may deserve the formation status.


ISSN: 1012-0750
EISSN: 1996-8590
Coden: TGSAA3
Serial Title: South African Journal of Geology
Serial Volume: 106
Serial Issue: 1
Title: Mesozoic fluvial deposits on a rifted continental margin near Vaalputs, Namaqualand, South Africa
Affiliation: University of the Witwatersrand, Department of Geology, Wits, South Africa
Pages: 11-16
Published: 200303
Text Language: English
Publisher: Bureau for Scientific Publications, Pretoria, South Africa
References: 21
Accession Number: 2003-082978
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
S30°19'60" - S30°19'60", E18°00'00" - E18°00'00"
Secondary Affiliation: South African Nuclear Energy Corporation, ZAF, South Africa
Country of Publication: South Africa
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200324
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