Dwyka Gr
Type Locality and Naming
Main Karoo Basin (SE), Main Karoo Basin (Eastern/Northern Forebulge), Aranos Basin, Waterberg Basin, Huab Basin, Owambo Basin, Kalahari Basin (SW), Kalahari Basin (Central), Kalahari Basin (NE), Mid-Zambezi Basin, Cabora-Bassa Basin, Springbok Flats Basin, Ellisras Basin, Tshipise Basin, Tuli Basin, Save Basin, Morondava Basin (Madagascar), Metangula Basin (Mozambique), Luangwa Basin (Zambia), Congo Basin (Lukuga-DR Congo)
Synonym: Dwyka Glacial Beds, Dwyka Tillite Formation, Basal Beds (Tuli Basin)
Lithology and Thickness
Massive glaciogenic diamictites, glacial till, subaqueous meltout tillites, varves (laminated couplets), and dropstone-bearing mudrocks. In the type basin, it can reach thicknesses of up to 800 meters. It is further divided into from uppermost to bottom: Kameelhaar Member, Viperstorf Member, Hardap Member, Keikanachab Member (Keykanachab), Gründorn Member (Grundorn), Faalgras Member, and Gibeon Member.
Relationships and Distribution
Lower contact
Rests unconformably on pre-Karoo basement rocks (ranging from the Palaeozoic Cape Supergroup to Palaeoproterozoic metamorphic complexes), frequently exhibiting a highly scoured and glaciated planar surface.
Upper contact
Conformably (in deeper basin centers) or unconformably (on basin margins) overlain by the post-glacial marine mudstones of the basal Ecca Gr, the Prince Albert Fm in the Main Karoo Basin.
Regional extent
Extremely widespread; forms the basal succession across almost all southern and central African Karoo basins, including the Main Karoo Basin, Kalahari Basins (Botswana), Ruhuhu Basin (Tanzania), and Congo Basin (DRC).
GeoJSON
Fossils
Age
Depositional setting
Additional Information