Draft:Griqualand West Basin

Griqualand west basin
Griqualand west basin
Highest point
Elevation	950 m (3,120 ft)
Coordinates	25°09′28″S 26°44′11″E
Dimensions
Length	350 km (220 mi)
Width	15 km (9.3 mi)
Geography
Country	South Africa
Provinces	Northern cape
Geology
Age of rock	Archean and proterozoic
Type of rock	Quartz arenites, shale and dolomite
Climbing
Easiest route	From Northwest or Vryburg

The Griqualand west basin occurs within the Transvaal basin 2.5 million years ago in the Northern Cape province. It was founded by the Khoisan people who are the xhosa natives.The karoo biome occurs within this basin.

Geology

In his 1986 study, Beukes posits that the sediments of the Griqualand West Sequence

The sediments were deposited in three major tectonic-sedimentary environments, including a shallow water platform. A platform edge and a deeper basin are present in the west and south-west of the continent. Stratigraphically, these environments correspond These are in turn correlated with the Schmidtsdrif Formation, the limestones and cherts. and cherts of the Ghaap Plateau Formation. Jaspilites of the Asbesberg Formation. The lower Schmidtsdrif Formation is composed of fluvially deposited quartz arenites and shallow-marine sediments, as well as a carbonate platform sequence. Carbonate platform sequence. In the basin located to the southwest of the platform. The sediments that overlie the carbonate platform sequence at the edge of the basin southwest of the platform are carbonaceous. Carbonaceous shales. The Ghaap Plateau Formation is characterised by the presence of stromatolitic deposits. The sediments consist of dolomite and limestone plateau deposits. In the direction of the In the basin, this facies is overlain by laminated limestone and dolomite. Dolomite, some of which are carbonate turbidites, is also present. In the basin, the turbidite sediments undergo ankeritisation. These sediments were subsequently ankeritised and partly silicified, resulting in the formation of banded ferruginous chert. Subsequently, these sediments were deposited with the carbonaceous shales within the basin. The limestone sequence of the platform was deposited in the basin. The entire platform sequence is completely dolomitised, with the exception of the edge. In areas where limestone-rich zones are preserved. The cessation of deposition of carbonates in the shallow water was caused by the transgression. The deposition of carbonates in shallow water on the shelf and the formation of microbands of iron are both processes that occurred concurrently.

Formations

Makganyene Formation Mixed sedimentation at the basal contact of the Makganyene Formation reveals intercalations between diamictite and lesser iron formation, shales, sandstones, and conglomerates in the area between Sishen and Rooinekke (de Villiers and Visser, 1977; Polteau and Moore, 1999; Visser, 1999). The main diamictite is a massive rock with poorly sorted clasts, some facetted and striated. Maximum class size decreases progressively westwards across the Griqualand West basin ( Visser, 1999). The basal intercalations with shale and sandstone include graded beds (diamictite-to-black shale) and occasional dropstones, indicating a transition to marine facies. Where the Koegas Subgroup underlies the Makganyene Formation, it consists of a similar diverse suite of rock types, and the contact between the two units is of an intercalated nature. The iron formations interbedded with the Makganyene diamictites are compositionally and isotopically similar to those of the underlying Koegas and Asbesheuwels Subgroups ( Polteau and Moore, 1999).Hotazel and Mooidraai Formations Iron formations in the Hotazel Formation immediately overlying the Ongeluk lavas, are similar in major, trace, and rare earth element composition and isotopic character to those of the Asbesheuwels and Koegas Subgroups beneath the Makganyene Formation (Tsikos and Moore, 1997; Tsikos, 1999). Taken as a single entity, the Ghaap–Postmasburg succession displays a symmetry: carbonate – iron formation – diamictite/lavas – iron formation – carbonate ( Fig. 3). Carbonate O and C stable isotope profiles reveal a progressive excursion to lighter values from Campbell and carbonates into Asbesheuwels iron formations (Beukes et al., 1990) that persists to the base of the Makganyene diamictite.