Revised definition/outline of the Kheis Terrane along the western margin of the Kaapvaal Craton and lithostratigraphy of the newly proposed Keis supergroup

The Kheis Province is situated between the Namaqua-Natal Province and the western margin of the Kaapvaal Craton in the Northern Cape Province of South Africa. It has been described as a thin-skinned fold and thrust belt formed between 1800 and 1700 Ma. The lithostratigraphic subdivision of the rock units comprising the Kheis Province has been a source of much controversy. From detailed study of aerial photography and satellite imagery, as well as field-based studies, the outcrop patterns in the Kheis Province and Kaaien Terrane were reinterpreted and a new stratigraphic subdivision is outlined here. It is proposed that the structural Kaaien Terrane and Kheis Province should be combined into the Kheis Terrane and that the rocks occurring in the Kheis Terrane should be grouped together to form the new Keis supergroup, with the basal metaconglomerate of the Mapedi/Gamagara Formation recognised as the regional unconformity between the Keis supergroup and the underlying rocks of the Transvaal Supergroup in the Griqualand West area. The Keis supergroup is subdivided from the base upwards into the Elim-, Olifantshoek-, Groblershoop-and Wilgenhoutsdrif groups. The basal Elim group is composed of the Mapedi/Gamagara-and Lucknow formations. It is overlain with a regional erosional unconformity by the Olifantshoek group, which is made up of the Neylan-, Hartley-, Volop-and Top Dog formations. The Olifantshoek group is conformably overlain by the Groblershoop group which is comprised of three upward coarsening successions: • the Faanshoek-and Faansgeluk formations, • the Maraisdraai-and Vuilnek formations and • the Opwag-and Skurweberg formations. The Groblershoop group is in turn erosively overlain by the rocks of the Wilgenhoutsdrif Group, which include the basal erosive Groot Drink formation which is overlain by the Zonderhuis-and Leerkrans formations. The lithologies of the Keis supergroup are in faulted contact with the rocks of the younger Areachap Group of the ~1200 Ma Namaqua-Natal Metamorphic Province.