Upper Grit unit Fm
Type Locality and Naming
Luangwa Basin (Zambia). A formal lithostratigraphic unit representing a massive, coarse-grained sequence within the Upper Karoo Group of the Zambian and Zimbabwean rift valleys (specifically the Luangwa and Mid-Zambezi basins). Uppermost unit in Stormberg Gr in Luangwa Basin (Zambia).
Synonym:
Lithology and Thickness
Composed of a thick succession of red-brown, coarse to very coarse pebbly feldspathic sandstones (grits and arkoses).
Relationships and Distribution
Lower contact
Unconformably (and in some places, transitionally) overlies the Red Marl unit Fm or the Ntawere Fm.
Upper contact
Represents the top of the preserved Upper Karoo sedimentary sequence in many areas. It is unconformably overlain by post-Karoo sediments (such as the poorly consolidated Cretaceous/Paleogene Luangwa Fm) or Jurassic volcanic rocks (like the Batoka Basalt Fm in the Zambezi system).
Regional extent
Widespread across the Karoo-aged grabens of Zambia and Zimbabwe, particularly forming major topographic features in the Luangwa and Mid-Zambezi basins. Correlates with the middle to upper Stormberg Gr (such as the Molteno Fm and Elliot Fm) of the Main Karoo Basin in South Africa. It is also chronostratigraphically and lithologically similar to the Pebbly Arkose Fm.
GeoJSON
Fossils
Age
Depositional setting
High-energy terrestrial, braided fluvial environments.
Additional Information