quarzites, vein quartz, banded ironstone, dolomite, gneiss, granite, and amygdaloidal lavas. It is currently accepted that the northern facies represents valley-fill deposits, proglacial outwash fans, and subglacial till deposits left by continental glaciers retreating towards the south of the early Karoo Basin. Glacial pavements where striation marks are left on the surface of basement rocks are known from this formation in numerous localities. North of the Karoo Basin outcrops of another geological formation that correlates in age to the main Karoo Basin's Dwyka-aged deposits. This formation is the lowermost unit of the Springbok Flats, Tshipise, northern Lebombo, Tuli, and Ellisras (Lephalale) Basins. This geological formation is recognized and differentiated below due to its unique lithological facies from its main Karoo Basin counterparts: Tshidzi Formation : Deposits of this formation represent backbulge basin deposits of the Karoo foreland system. In the Tshipise and Tuli Basins, this formation is known as the Madzaringwe Formation. This formation consists of pebbly mudstones that are interbedded with mainly coarse-grained diamictites. These deposits are considered to be lacustrine facies, which show that the rock sediments were deposited in glacial or periglacial lakes. The northernmost Dwyka Group deposits are considered to have been most proximal to the shoreline of the shallow interior sea that was present at this time in southern Africa. Paleontology The Dwyka Group is mainly known for petrified wood which increase in species diversity in the younger sequences. The cold, glacial environment that the sedimentary rocks of the Dwyka Group were deposited in was not conducive for high plant diversity. Fossil wood species identified include lycopods, especially from the Karasburg, Kalahari, and Huab Basins in Namibia. Glossopteris leaf impressions, the petrified remains of Dadoxylon, coprolites, fossil pollen, and trace fossils of bony fishes, crustaceans, and other arthropods have been found from the Dwyka Group and correlated geological formations from other basins. See also References Geologic groups of Africa Geologic formations of Namibia Geologic formations of South Africa Geologic formations of Zimbabwe Carboniferous System of Africa Carboniferous South Africa Permian System of Africa Permian South Africa Carboniferous south paleopolar deposits Permian south paleopolar deposits Karoo Supergroup