Geology > Pre-Karoo > Ventersdorp Supergroup

Ventersdorp Supergroup

Introduction

The Ventersdorp Supergroup is dominated by andesitic lavas interlayerd with subordinate agglomerate and conglomerate tuff units. The Ventersdorp Supergroup uncomformably overlies the Witwatersrand Supergroup. This Group is very thick, more than 4500m. Outcrops mostly occur in the Northern Cape and Western Transvaal. The lower Kliprivierberg Group is mafic lava and tuff. The upper Platberg Group is conglomerates and breccia on top of Kliprivierberg, with intermediate and felsic lava higher, with quartzite, shale and siltstone layers in between.

Geohydrology

•	Flat areas, with a lot of pans, draining into the lavas.

•	Main areas: West Transvaal and Northern Cape, from Heidelberg to Prieska.

•	South-west Transvaal: Wolmaranstad to Vryburg and Mafikeng – groundwater shallow, with high yields in lavas due to deep weathering and large fractures during cooling process. Yield directly related to rainfall.

•	Near Johannesburg: Large yields in small outcrop between Kempton Park and Braamfontein.

•	Rustenburg-Marico: Quartzites with lava on top. In sedimentary rocks 1l/s and in lavas 0.7l/s.

•	Northern Cape: In weathered areas, and where limestone is present. Calcite formations a good area to site boreholes due to erosion.

Ventersdorp

Source: http://www.vdome.co.za