Pebbly Arkose Fm
Type Locality and Naming
Mid-Zambezi Basin, Cabora-Bassa Basin. Defined from extensive mapping in the Zambezi Valley of Zimbabwe and Zambia. It is a very prominent, ledge-forming stratigraphic unit in the region's Upper Karoo sequence. Upper formation in Stormberg Gr in Mid-Zambezi Basin.
Synonym:
Lithology and Thickness
A high-energy, coarse clastic succession. As the name implies, it is dominated by coarse-grained, heavily cross-bedded feldspathic sandstones (arkose) containing abundant, widely dispersed pebbles of quartz and feldspar. Intercalated within these massive sand bodies are minor lenses of red to greenish siltstones and mudstones.
Relationships and Distribution
Lower contact
Rests (often with a localized erosional unconformity or scour surface) upon the finer-grained fluvial and overbank deposits of the underlying units, typically referred to as the Fine Red Marly Sandstone Fm or Ripple-Marked Flags Fm in traditional Zimbabwean stratigraphy (or the Escarpment grit Fm where intervening units are eroded/absent).
Upper contact
Conformably and transitionally overlain by the massive, fine-grained aeolian deposits of the Forest Sandstone Fm.
Regional extent
Widespread across the rift basins of Zimbabwe, southern Zambia, and western Mozambique. It forms prominent topographical ridges and escarpments in the Zambezi Valley. Lower Stormberg Gr equivalent. It chronostratigraphically correlates broadly with the Molteno Fm and lower Elliot Fm in the Main Karoo Basin of South Africa, and the Mosolotsane Fm in Botswana.
GeoJSON
Fossils
Age
Depositional setting
High-energy, continental braided river environments.
Additional Information