Добірка наукової літератури з теми "Adelaide Supergroup"

Abstract The middle Permian Eodicynodon Assemblage Zone is the lowermost biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup) and occurs in the southwestern part of the main Karoo Basin. It is host to a diverse assemblage of basal therapsid genera of which Eodicynodon is the most abundant. The biozone reaches a maximum thickness of 1 100 m in the Prince Albert Road area and thins to the east and west. The biozone corresponds to the Combrinkskraal and Grootfontein members of the Abrahamskraal Formation, directly overlies the Waterford Formation of the Ecca Group, and records the earliest middle Permian terrestrial environments of Gondwana. Rocks of the biozone were deposited along the southern shoreline of the Karoo Basin in a subaerial delta plain environment as part of large-scale fan systems draining to the north and northeast within a second-order highstand systems tract.

Abstract The Endothiodon Assemblage Zone is the third oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup). It is situated between the underlying Tapinocephalus and overlying Cistecephalus assemblage zones and in the southwestern part of the basin corresponds to the majority of the Poortjie and Hoedemaker members of the Teekloof Formation. It is characterised by the dicynodont genus Endothiodon, especially in the lower part of assemblage zone, and records early ecosystem recovery from the Capitanian mass extinction. It also contains the lowest occurrence in the Karoo Basin of cynodont therapsids, eutherocephalians, bidentalian dicynodonts, and diapsids. The biozone reaches a maximum thickness of around 250 m in the southwestern part of the basin. We propose a two-fold subdivision into a lower Lycosuchus - Eunotosaurus Subzone (equivalent to the upper two-thirds of the former Pristerognathus Assemblage Zone) and an upper Tropidostoma - Gorgonops Subzone (equivalent to the former Tropidostoma Assemblage Zone), with the contact defined by the first appearance of Tropidostoma dubium. The Endothiodon Assemblage Zone is terminated by the first appearance of Aulacephalodon bainii.

Abstract The Tapinocephalus Assemblage Zone is the second oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup), biostratigraphically positioned between the underlying Eodicynodon and overlying Endothiodon assemblage zones. It is characterised by a rich fossil tetrapod assemblage comprising basal members of most therapsid clades, but particularly dinocephalians such as Moschops capensis and basal pareiasaurs such as Bradysaurus in co-occurrence with the pylaecephalid dicynodonts Robertia and Eosimops. It corresponds to the upper two thirds of the Abrahamskraal Formation, is Capitanian (Guadalupian) in age, and reaches a maximum thickness of around 1500 m. The biozone is here separated into two subzones: a lower Eosimops – Glanosuchus Subzone and an upper Diictodon – Styracocephalus Subzone. The contact between the two subzones is defined by the first appearance of Diictodon feliceps, which closely corresponds to the base of the Moordenaars Member. The uppermost part of the biozone contains the Capitanian mass extinction and the low diversity fauna in its immediate aftermath. The zone is terminated by the first appearance of Endothiodon bathystoma.

Abstract The stratigraphy of the Ecca Group has been subdivided into the Prince Albert, Whitehill, Collingham, Ripon, and Fort Brown Formations in the Eastern Cape Province, South Africa. In this article, we present detailed stratigraphic and facies analyses of borehole data and road-cut exposures of the Ecca Group along regional roads R67 (Ecca Pass), R344 (Grahamstown-Adelaide), R350 (Kirkwood-Somerset East), and national roads N2 (Grahamstown-Peddie) and N10 (Paterson-Cookhouse). Facies analysis of the Ecca Group in the study area was performed to deduce their depositional environments. Based on the lithological and facies characteristics, the stratigraphy of the Prince Albert, Whitehill, Collingham, and Fort Brown Formations is now subdivided into two informal members each, while the Ripon Formation is subdivided into three members. A total of twelve lithofacies were identified in the Ecca Group and were further grouped into seven distinct facies associations (FAs), namely: Laminated to thin-bedded black-greyish shale and mudstones (FA 1); Laminated black-greyish shale and interbedded chert (FA 2); Mudstone rhythmite and thin beds of tuff alternation (FA 3); Thin to thick-bedded sandstone and mudstone intercalation (FA 4); Medium to thick-bedded dark-grey shale (FA 5); Alternated thin to medium-bedded sandstone and mudstone (FA 6); and Varved mudstone rhythmite and sandstone intercalation (FA 7). The FAs revealed gradually change of sea-level from deep marine (FA 1, FA 2, FA 3 and FA 4, FA 5, and FA 6) to prodelta environment (FA 7). This implies that the main Karoo Basin was gradually filling up with Ecca sediments, resulting in the gradual shallowing up of the water depth of the depositional basin.

Abstract Fossil wood is described from the Late Permian Middleton Formation, Adelaide Subgroup, Beaufort Group of the Karoo Supergroup in the Easter Cape Province, South Africa. The wood consists of in situ tree trunks up to 9 m long, partially enclosed in fine-grained sandstone surrounded by argillaceous mudstone and siltstone. The strata are poorly exposed due to the eroded and denuded land surface. All are lying horizontally and none are in upright growth positions. Comparisons of the study site lithologies with known surrounding Middleton Formation lithostratigraphy supports the interpretation that the palaeoenvironment responsible for the transport and deposition of the fossil wood was fluvial, with sandstone representing in-channel deposits and the mudstone-siltstone flood plain sequences where the trees were originally located before being uprooted and transported within the channels. Thin sections of twenty-nine wood samples revealed the presence of four existing taxa, Agathoxylon africanum, Agathoxylon karooensis, Australoxylon natalense and Australoxylon teixeirae. Growth rings of all the samples show a wide range of ring width from 1 mm to 11 mm, indicating growth under suitable climatic regimes with adequate water supply interspersed by very wet and warm periods. Crushed earlywood, s-shaped cell walls and torn cell walls suggest felling of trees during storm and/or flood events followed by sedimentary transport in palaeochannels prior deposition within the channel sands.