Abstract:
The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide
extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye
sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic
and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations.
Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and
valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed
in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek
Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is
unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort
farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed.
A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are
proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous
province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one
of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.
