Lower Wankie Sandstone Fm
Type Locality and Naming
Mid-Zambezi Basin (Zimbabwe and southern Zambia) Named after the Hwange (formerly Wankie) district in northwestern Zimbabwe. It was described during the early 20th-century geological surveys of the Wankie coalfields by geologists such as B. Lightfoot and A.J.C. Molyneux, designated as the foundational sedimentary unit sitting beneath the main economic coal seams.Lowermost formation in Ecca Gr in Mid-Zambezi Basin
Synonym:
Lithology and Thickness
A fining-upward clastic sequence typically ranging from 30 to 45 meters in thickness. It frequently begins with a coarse, patchy basal conglomerate containing large, angular clasts derived directly from the underlying basement. This grades upward into massive, coarse-to-medium-grained, cross-bedded, grey to white feldspathic sandstones (arkose). The upper portions of the formation become progressively finer, passing into thinly bedded, highly micaceous, flaggy sandstones and siltstones.
Relationships and Distribution
Lower contact
Rests with a profound regional unconformity directly upon the ancient Precambrian metamorphic and igneous basement rocks (such as the Kamativi Inlier). The basement topography was uneven, meaning the Lower Wankie Sandstone frequently filled in ancient valleys and depressions. (In some localized, deeper paleovalleys, it may rest on patchy, thin remnants of glaciogenic Dwyka Glacial Beds Fm).
Upper contact
Conformably and transitionally overlain by the highly carbonaceous mudstones and thick coal seams of the Black Shale and Coal Gr (Wankie Coal Fm).
Regional extent
Found along the margins and in the subsurface of the Mid-Zambezi Basin in Zimbabwe, particularly well-documented in the Hwange coal mining district. Basal Ecca Gr equivalent (and partially Dwyka Gr equivalent at its absolute base). It broadly correlates with then in Botswana and the Siankondobo Sandstone in Zambia.
GeoJSON
Fossils
Age
Depositional setting
Fluvial and localized fluvioglacial environments.
Additional Information