Upper Madumabisa Mudstones Fm
Type Locality and Naming
Mid-Zambezi Basin. Named after Madumabisa Hill near Hwange (formerly Wankie) in northwestern Zimbabwe. Included in Beaufort Gr in Mid-Zambezi Basin and Luangwa Basin (Zambia)
Synonym:
Lithology and Thickness
The entire Madumabisa Mudstone succession is incredibly thick (up to 700 meters) and was formally subdivided into Lower, Middle, and Upper divisions by the pioneering geologist Geoffrey Bond based on distinct paleontological and lithological changes.
Dominated by a massive, monotonous succession of non-carbonaceous, pale greenish-grey to bluish-grey mudstones and calcareous siltstones. Towards the top, it frequently takes on reddish or purplish hues. A highly diagnostic feature of the Upper Madumabisa is the abundance of localized limestone beds and large calcareous concretions (septarian nodules).
Relationships and Distribution
Lower contact
Conformably and transitionally overlies the Middle Madumabisa Mudstones Fm
Upper contact
Sharply and unconformably overlain by the massive, coarse-grained conglomeratic sandstones of the Escarpment grit Fm.
Regional extent
Widespread across the rift basins of Zimbabwe (Zambezi Basin) and Zambia (extending notably into the Luangwa Valley, where it is highly fossiliferous). Lower Beaufort Gr equivalent (Thabala Fm).
GeoJSON
Fossils
Age
Depositional setting
Expansive, shallow inland lakes and vast, low-energy terrestrial floodplains. The Upper Madumabisa Mudstones represent a long period of tectonic stability in south-central Gondwana. The environment was characterized by vast, sluggish, muddy floodplains surrounding shallow, alkaline lakes (which precipitated the limestone nodules). The climate was relatively warm and semi-arid, supporting large herds of roaming dicynodonts along the vegetated lake margins.
Additional Information