Mountain Zebra National Park's Geology October 6th, 2017

Geological Information

The geological formations within the Mountain Zebra National Park consist of sandstone, siltstone and mudstone of the Beaufort Group and the Karoo Supergroup, with dolerite sills and dykes.

The Park can be broadly classified into three land forms:

1. Mountain highlands rugged landscape

The mountain highlands rugged landscape is strongly associated with rocky outcrops which cover about 60 - 80% of the mountainous area of the Park. The steep mid-slopes hold the most prominent topographical position in this mountainous landscape, with the dominant soil-rock complex consisting of rock.  The geology of this landscape consists of dolerite with mudstone, shale and sandstone.

2. Middle plateau rolling landscape

The middle plateau rolling landscape consists of a soil pattern where duplex soil forms, such as Swartland and Valsrivier, are prevalent. These plains are dominated by plateau mid-slopes but also include the steep mid-slopes and foot-slopes topographical positions. The geology of this landscape is mudstone, shale and sandstone.

3. Valley bottomland undulating plains landscape

The valley bottomland undulating plains landscape, is strongly associated with young landscapes, which are predominantly rocky and alluvial. It refers to land where lime occurs regularly in upland and valley-bottom soils.  Soil forms that epitomise this land type are Glenrosa and Oakleaf. The geology of this landscape consists of mudstone, shale and sandstone, with rare dolerite intrusions.  Two topographical positions, the valley bottomlands and drainage lines including the Wilgerboom River, are prominent in this terraced landscape.

The soils derived from doloritic material are more resistant to erosion than those which have evolved from shale and mudstone. This is due to the chemical and mineral composition of the dolerite. Chemical weathering is secondary in importance to mechanical weathering in the Mountain Zebra National Park due to the dry climate.

The steep slopes and scattered vegetation coupled with the frequent occurrence of thunderstorms, accelerates the transportation of weathering products to the well vegetated lower lying areas where deposition takes place. Due to good drainage, most of the surface water disappears underground in the lower lying sandy plains. A number of fountains are present which ensure a relatively permanent supply of surface water.

For more information on this article and others look out for the Mountain Zebra National Park Official Guide book found at any National Park.