The geology of area 2615C Lüderitz, South West Africa

Abstract

Abstract provided by author:

The Bogenfels Formation is represented in the southeastern quarter by a basal sedimentary assemblage consisting of interbedded grit and dolomite, above which lies a further sequence of banded dolomite. It rests unconformably on the basement formation. To the northwest remnants of Bogenfels material are present in a zone of thrust faults. Here also the Diaz Point Formation, consisting of boulder conglomerate and thin bands of quartzite, is present in thrusted contact with the basement formation

Lamprophyric dykes, including cemptonite and vogesite, cut the thrust faults, and occur in the basement formation throughout the area. Dolerite dykes of unknown age but later than the basement formation, are present at two sites

The Elizabeth Bay Formation, consisting of fluviatile grit, clay lenses, and eolian sandstone, occupies topographic depressions in the western half of the area. Fossils found in the clay indicate that it is possibly of Miocene age

A belt of barchan dunes, part of the mass which extends to Walvis Bay, is present in the centre of the area. Elsewhere the terrain is deflated, barring the immediate coastline

The major structural units consist of a syncline and an anticline in the basement formation in the western half of the area. These show the eastward trend of the. primary deformation. A second deformation has formed a northward-closing arch in the basement formation and was probably accompanied by major reverse faulting, palingenesis of the central adamellite stocks, and genesis of augen gneiss

The younger Bogenfels deformation folded the sediments around a northward trending axis, and later faulting displaced both Bogenfels and basement material

The most important economic mineral occurrence consists of diamonds, which have now been mined out