Bori Fm
Type Locality and Naming
Central Kalahari Sub-basin, Botswana. Like many units in the Kalahari Basin, it was formally mapped and defined primarily from extensive coal and groundwater boreholes by the Botswana Geological Survey, alongside isolated stream exposures. Lower formation in Ecca Gr in Kalahari Basin (Central)
Synonym:
Lithology and Thickness
Dominated by a thick basinal sequence of grey to dark brown and black carbonaceous mudstones and argillites. The upper portions frequently contain interbedded siltstones and thin sandstone lenses that often exhibit planar parallel lamination depicting fining-upward pulses.
Relationships and Distribution
Lower contact
Conformably overlies the post-glacial and glaciolacustrine deposits of the Dwyka Gr, or rests directly and unconformably on the Archean/Proterozoic basement where the Dwyka is absent.
Upper contact
Conformably and transitionally overlain by the massive, coarse-grained fluvio-deltaic sandstones of the Kweneng Fm (Middle Ecca equivalent).
Regional extent
Widespread across the subsurface of the Central and Southern Kalahari Basin in Botswana. Lower Ecca Gr equivalent. It chronostratigraphically correlates with the Makoro Fm and Tswane Fm in the eastern and northern Botswana sub-basins, and broadly with the Prince Albert Fm and Pietermaritzburg Fm in the Main Karoo Basin of South Africa.
GeoJSON
Fossils
Age
Depositional setting
Post-glacial marine to expansive lacustrine (pro-delta) environments.
Additional Information