Geology > Post Karoo > Tertiary Deposits

Tertiary deposits South Africa

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

Introduction

During the Cenozoic sea-level began to fall from the high levels experienced during the Cretaceous. A series of large coast-parallel dune complexes developed along most of the South African coastline. Recent coastal dunes can contain economic concentrations of minerals such as ilmenite, rutile and zircon, which are mined near Richards Bay. The ilmenite and rutile is smelted to produce titanium metal and white pigments (mostly for paint). The zircon is used for glazing on tiles and pottery, and as a metal alloy. Many of these coastal deposits consist of alluvium, lime-rich marine deposits, sandstone and conglomerates.

The Kalahari sediments have accumulated by either lateral surface inputs or in situ weathering, and in the process incorporated a range of environmental indicators, which lend themselves to palaeoenvironmental interpretation. In particular the depositional basins have accumulated lake sediments of local and sub-regional origins. The Kalahari sands (Vryburg, Mafekeng, Postmasburg and Gordonia) are rich in limestone and sandstone, with lime-rich clay layers. They are covered with youngwer wind deposited sand.

dune

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

Geohydrology

•	Kalahari sands are up to 200m thick. Most important aquifers are the limestone conglomerates and lime-rich sandstone. Due to low rainfall is recharge low and water table is 60-150m deep. Water mostly in older layers below sands.

•	Coastal aquifers have shallow water tables with many springs. Water originates from inland drainage channels. Their yields vary between 0.8-1.4 l/s, however they can be as high as 12l/s.