Volume 25 1984
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- ItemPalaeontologia africana Volume 25(Bernard Price Institute for Palaeontological Research, 1984)
- ItemA review of the Stormberg Group and Drakensberg volcanics in southern Africa(Bernard Price Institute for Palaeontological Research, 1984) Visser, J. N. J.The Molteno Sandstone, Red Beds and Cave Sandstone comprising the Stormberg Group (siliciclastics) in South Africa and their correlatives, based on lithology, depositio- nal environments and tectonic cycles, in Zimbabwe, Botswana and Namibia are described. The Drakensberg Volcanics with radiometric ages of 114 My to 194 My cap the sedimen- tary sequence. A major unconformity separates the Stormberg sedimentary rocks from the lower Karoo strata. Four Late Triassic depositional basins which were tectonically controlled are recognised. The Molteno Sandstone and Red Beds filling these basins represent braided and meandering stream deposits respectively. The Cave Sandstone covering the fluvial deposits formed as desert sand sheets reworked by westerly winds. Deposition was ended by the outpouring of the Drakensberg Volcanics.
- ItemPalaeogeographic implications of braid bar deposition in the Triassic Molteno formation of the eastern Karoo Basin, South Africa(Bernard Price Institute for Palaeontological Research, 1984) Turner, Brian R.The Triassic Molteno Formation in the main Karoo Basin, South Africa, forms a northerly thinning intracratonic clastic wedge deposited by sandy braided rivers of South Saskatchewan type. Deposition of the sandy facies was dominated by channel floor mega-ripples producing trough cross-bedded cosets; transverse bars, represented by solitary, large-scale planar sets are not significant. Departures from this regional pattern of sandstone deposition occur along the northern distal margin of the Molteno basin around Bethlehem in the Orange Free State. Here thickness trends and clast size delineate a deep channel system interpreted as the main braided exit channel from the basin. Because of its depth and constriction by local height differentials the competency and capacity of the flow were able to reproduce features more typical of proximal rather than distal depositional settings. The sandy facies is dominated by fine gravel with lesser amounts of coarse sand. Gravel occurs as longitudinal bars some of which contain low angle foreset stratification whose orientation is consistent with lateral growth and marginal riffle migration. The scale of the bars and simple deposi- tional form imply that they may have been larger than modern equivalents and the flows deeper. The coarse sand occurs mainly as falling water stage features associated with the gravel bars. Shallow channel-fills, bar edge sand wedges, bar top sheet sands and thicker channel sands have been recognised and compared with similar features in modern and ancient braided stream sediments. When traced to the southeast the deep channel sediments contain few longitudinal gravel bars and more transverse bars; the vertical sequence from longitudinal to transverse bars at this locality points to the increasing distality of the depositional site through time.
- ItemBiostratigraphy and paleontology of some conchostracan-bearing beds in southern Africa(Bernard Price Institute for Palaeontological Research, 1984) Tasch, PaulThe present field and laboratory study was undertaken in conjunction with a monograph being prepared on Gondwana estheriids. Detailed biostratigraphic reports are lacking on the southern African conchostracan-bearing beds. The available paleontological treatment ranges from mere mentions of certain fossils being present to spare systematics. During the summer of 1979 a limited exploration program was undertaken at localities in the Clarens Formation (Cave Sandstone) outcrop belt where conchostracans had been reported (Stockley 1947, Haughton 1924, and especially Ellenberger et al. 1964). In particular, sites at Siberia and Barkly Pass (both in the Republic of South Africa) and at Thabaneng and Mofoka's Store (both in Lesotho) were found to yield excellent new biostratigraphic and paleontological data. The exploration covered some 1500 square miles (2400km2 of the Clarens Formation (Cave Sandstone) outcrop belt (Text fig. 1). Conchostracan-bearing Cave Sandstone sites noted by Paul Ellenberger (1970) at Leloaleng, Masitisi, Mohaleshoek, Brakfontein and elsewhere were systematically explored. Because of the lack of precise locality data enabling one to pinpoint the fossiliferous bed(s) even an intensive search did not uncover the reported fossiliferous beds. Exploration of one of Ellenberger's localities at Wonderkop (RSA) was abandoned after a preliminary search due to time limitations. This site may yet prove productive.
- ItemPostcranial remains of Fabrosauridae (Reptilia: Ornithischia) from the Stormberg of southern Africa(Bernard Price Institute for Palaeontological Research, 1984) Santa Luca, A. P.The postcranial skeletons of three fabrosaurids from the upper Elliot Formation "Red Beds" of the Stormberg Group in southern Africa are described. The material demonstrates details of fabrosaurid anatomy previously unknown, particularly a short, deep prepubic process which is undoubtedly primitive for the Ornithischia. Besides the short prepubis, fabrosaurids are characterized by 1) a reduced manus; 2) an ilium having a lateral extension of the supra-acetabular margin and a deep nearly vertical brevis shelf; and 3) an elongated hindlimb. Postcranial morphology excludes the fabrosaurids from the ancestry of the contemporaneous heterodontosaurids. Neither can the fabrosaurids be considered ancestral to the 'juvenile scelidosaurid' (BMNH R6704) as has been suggested. On the contrary, the 'scelidosaurid' is more primitive in structure than fabrosaurids. The assignment of Nanosaurus agilis Marsh to the Fabrosauridae is not substantiated after morphological comparisons between the postcranial material of both. The taxonomic status of Scutellosaurus lawleri is regarded as uncertain. The fabrosaurids are more similar to the Morrison Formation camptosaurids, than to Hypsilophodon. Finally, it is argued that ornithopods were not a basal stock for the phylogenesis of non-ornithopods but represent an independent radiation comparable to the other ornithischian suborders. The fabrosaurids were an early development of the ornithopod radiation itself.