Geology > Post Karoo > Drakensberg and Lebombo Group

Drakensberg and Lebombo Group

Taken from http://www.geology.ukzn.ac.za

Introduction

Dramatic outpourings of lava spread across much of Gondwana about 180 million years ago heralding the start of Gondwana breakup. Remnants of these once extensive lavas now form the Lesotho highlands and Lebombo mountains.

A 1.5 km thick accumulation of Jurassic age basalt flows can be seen along the Drakensberg Escarpment. The magma (molten rock) made its way to the surface along a complex system of fractures. Crystallisation of magma within these fractures formed dolerite sills and dykes. The sills often form flat areas and weather to form a very dark red soil. The sill may also form resistant cliffs such as at Howick Falls. The final volcanic event produced rhyolite lava which now forms the Lebombo mountains. These volcanic events were followed by uplift and faulting that eventually separated Africa and Antarctica.

Geohydrology

•	Borehole productivity and spring discharge varies from 0.1 – 3 l/s.

•	Perched aquifers are localized both in the uppermost and weathered zones of the formation.

•	Intrusive rock represented by dolerite dykes and sills and kimberlite have moderate groundwater potential. Borehole and spring discharge ranges from 0.3 l/s to 4 l/s.

dykeoutline