South Africa Highlands

Geology

The scenery is one of the outstanding features of the Natal Drakensberg range and is among the finest in the world. The range is renowned for its sheer rock faces, spectacular free standing peaks, towering buttresses, deeply eroded river valleys and fascinating sandstone formations.

The geological formations of the Natal Drakensberg belong to the Karoo Sequence which, from the base upwards, consists of the Upper Beaufort Beds of the Beaufort Group and the Molteno, Elliot, Clarens Sandstone and Drakensberg Basalt formations of the Stormberg Series.

The Upper Beaufort Beds are the older sedimentary formation and therefore the lowest. They were laid down some 200 million years ago under extremely wet conditions when much of South Africa was covered by swamps. They consist of several red, green and maroon shales overlain by yellow fine grained sandstone with shales.

The Molteno Beds were deposited about 180 million years ago. They are recognizable as successive beds of sandstone, alternating with layers of blue and grey shales which accumulated in a vast inland lake. These sediments form the terraces and ledges at the foot of the Little Berg and are best seen in the Southern Berg.

The Elliot Formation, formerly known as the Red Beds, was laid down about 170 million years ago and consists of alternating beds of red shales and fine grained sandstone. This formation is rarely exposed and is best seen in the stream beds below the Clarens Sandstone Formation (formerly Cave Sandstone) and along paths. It forms the steeply vegetated slopes below the Clarens Sandstone Formation.

The Clarens Sandstone Formation is the most prominent of the sedimentary units exposed in the Drakensberg. The distinctive creamy white cliffs are a characteristic feature of the Drakensberg foothills and the sandstone layer forms the Little Berg. These beds are about 160 million years old and were originally laid down as desert dunes in a very arid climate during the Jurassic Period. The formation originally took its name from the large number of caves and shallow overhangs occurring at the base of the thick sandstone layer.

The highest part of the Berg was formed by lava flows, and is known as the Drakensberg Basalt Formation. Between the Middle Jurassic and early Cretaceous periods volcanic activity resulted in the flow of lava from fissures associated with the break up of the supercontinent, Gondwana.

Individual flows have been traced for more than 32 km (20 miles) and the lava flows varied in thickness from 0.3 to 45 m (1' to 150') and built up to a thickness of over 1,300 m (4,264'), covering what is today known as KwaZulu/Natal. The dolerite dykes and sills associated with the Karoo rocks underlying the Drakensberg lavas represent magma (molten matter) that did not reach the surface to form basalt flows. These vertical sills and horizontal dykes have been exposed through subsequent erosion.

The present rugged landscape of the Drakensberg has been formed by headward erosion of the Great Escarpment following the break up of Gondwana The erosion has been aided by seaward tilting of the KwaZulu/Natal coastal area and four successive periods of continental uplift.

© Article copyright Menasha Ridge Press. All rights reserved.


Published: 29 Apr 2002 | Last Updated: 15 Sep 2010
Details mentioned in this article were accurate at the time of publication

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