Hammanskraal Formation

Hammanskraal Fm

Period:

Permian

Age Interval:

Early-Middle Permian (Asselian-Roadian)

Province:
SouthAfrica-Namibia-Botswana

Type Locality and Naming

Springbok Flats Basin. Named after the town of Hammanskraal, situated just north of Pretoria. It was formally established as a distinct lithostratigraphic unit by the South African Committee for Stratigraphy (SACS) to represent the coal-bearing middle Karoo strata uniquely preserved within the isolated, structurally controlled Springbok Flats Basin. Includes in Ecca Gr in Springbok Flats Basin

Synonym:

Lithology and Thickness

A classic siliciclastic, coal-bearing succession. The formation is composed of alternating cyclic sequences of light-colored, medium- to coarse-grained cross-bedded sandstones, grey to black carbonaceous shales, mudstones, and multiple seams of bituminous coal. It can reach thicknesses of around 100 to 120 meters in the deeper troughs of the basin.

Lithology Pattern:

Coal

Relationships and Distribution

Lower contact

Conformably overlies the thin glaciogenic and post-glacial diamictites/mudstones of the Tshidzi Fm (the local Dwyka Gr equivalent). Where the Tshidzi is absent due to paleotopography, the Hammanskraal Fm rests with a profound unconformity directly upon ancient Precambrian basement rocks (such as the Bushveld Igneous Complex or the Waterberg Gr).

Upper contact

Unconformably overlain by the Triassic mudstones and sandstones of the Irrigasie Fm.

Regional extent

Middle Ecca Gr equivalent. It chronostratigraphically and environmentally correlates directly with the economically vital Vryheid Fm in the Main Karoo Basin, and the coal measures of the Waterberg, Soutpansberg, and Ellisras basins.

GeoJSON

null

Fossils

Age

Early-Middle Permian (Asselian-Roadian)

Age Span:

Beginning stage:

Asselian

Fraction up in beginning stage:

0.1

Beginning date (Ma):

298.35

Ending stage:

Roadian

Fraction up in the ending stage:

1.0

Ending date (Ma):

269.21

Depositional setting

Broad fluvio-deltaic, coastal plain, and extensive paludal (peat swamp) environments.

Depositional pattern:

Additional Information

Compiler:

From the O. Catuneanu et al. / Journal of African Earth Sciences 43 (2005) 211–253; Johnson, M.R., et al. (2006): Sedimentary rocks of the Karoo Supergroup. In: The Geology of South Africa; SACS (1980): Stratigraphy of South Africa.