Abstract
The Gamagara/Mapedi and Lucknow Formations of the Elim Group, along with the Olifantshoek
Group, within the Paleoproterozoic Keis Supergroup, are very important stratigraphic units.
Their economic importance is due to the presence of the oldest known red bed successions which
hosts well preserved lateritic soil profiles, as well as the ancient supergene high-grade laminated
iron ores of the Sishen-Postmasburg area on the Maremane dome. These high-grade iron ore
deposits are associated with the pre-ElimlGamagara unconformity, which is located at the base
of the conglomerate unit of the GamagaralMapedi Formation known as the Doornfontein
Member.
The main focus of the study i3 on the lateral correlation of the Elim Group in the Griqualand
West area to geology in the Highveld region of South Africa, with specific focus on the
depositional age of the Elim Group, i.e. the Gamagara/Mapedi and Lucknow Formations. The
depositional age, as well as the lateral correlation of the Elim Group, has however remained a
matter of contention, and this succession has previously been correlated with the Dwaalheuwel-
Magaliesberg succession of the upper Pretoria Group of the Transvaal Supergroup, and more
recently correlated to the Swaershoek- and Alma Formations of the lower Waterberg Group. The
correlation of the Elim Group to geology in the Highveld region of South Africa area is however
problematic as there is stratigraphic duplication of the red beds in the Elim and Olifantshoek
Groups, as well as strata from the Transvaal Supergroup within the Griqualand West area, caused
by intense folding and faulting. A higher degree of certainty, regarding the age constraints of the
Elim Group, and more specifically the Doornfontein Member of the Gamagara/Mapedi
Formation, is thus required to assist with a re-evaluation of the lateral extent and depositional age
of the high-grade iron ore deposits in the Highveld area as well as its correlation to geological
successions elsewhere in South Africa.
The age constraints for the GamagaralMapedi and the lower Lucknow Formations were obtained
from U-Pb geochronological studies of detrital zircon populations that were extracted from
various samples from the Gamagara/Mapedi and lower Lucknow Formations. The detrital zircon
grains were analysed by means of Laser Ablation Inductively Coupled Mass Spectrometry (LAICP-
MS) at the analytical facility Spectrum, at the University of Johannesburg...
M.A. (Geology)