Beaufort Group Research Articles

Silicified fossil woods from the Late Permian Middleton Formation, Beaufort Group, Eastern Cape Province, South Africa and their palaeoenvironmental significance

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.

Lithostratigraphy, sedimentary petrography and geochemistry of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin, Botswana

The Kalahari Karoo Basin of Botswana is an intracratonic basin developed in south-central Gondwana and is filled with Upper Carboniferous–Lower Jurassic Karoo Supergroup volcano-sedimentary units. The Karoo Supergroup units are unconformably covered by the Cretaceous to recent Kalahari Group. The Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana consists of the lacustrine sediments of the Beaufort Group (Tlhabala Formation), overlaid unconformably by the continental sediments of the Lebung Group, and by the continental basalts of the Stormberg Group. The Late Triassic to Early Jurassic Lebung Group is subdivided into the Mosolotsane Formation and the Ntane Formation. This sedimentary sequence is poorly exposed, and formation boundaries are tentatively identified by lithological changes in boreholes. Here, new sedimentological and geochemical data are used for the refinement of the stratigraphy of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana, new criteria for the identification of unit boundaries are set and provenance of the Lebung Group sediments has been defined. The geochemical investigation of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana revealed clear geochemical markers that have allowed the pinpointing of unit boundaries between the Tlhabala Formation (Beaufort Group), Mosolotsane Formation (lowermost Lebung Group). The sediments from the Tlhabala Formation have a geochemical signature typical of wackes, while the sandstones from the overlying Mosolotsane Formation and the Ntane Formation are dominated by arkose to subarkose. The transition from wacke to subarkose pinpoints the boundary between the Beaufort Group and the base of the Lebung Group. The Tlhabala Formation is characterized by increasing SiO2/Al2O3 ratio, with a maximum at the base of the Lebung Group, and by an upward decrease in the abundance of Na, K and transition metals such as Cr, Mn and Fe. The SiO2/Al2O3 ratio decreases upward in the Lebung Group. Similarly, the abundances of Na, K, Cr, Mn and Fe slightly increase upward only to show a negative peak at the Lebung Group and the Kalahari Group boundary. This contact is marked by a clear increase in the total REE content.The chemical composition of the Lebung Group sandstones also indicates a quartzose sedimentary provenance. The CIA (chemical index of alteration) values for these sandstones ranged from 63 to 73, indicating a high degree of chemical weathering. This type of intense weathering should produce high volumes of clay minerals, which are rather scarce in the studied samples. This indicates that the large amount of quartz in the Lebung Group has been recycled from the Paleoproterozoic sedimentary sequences of the Palapye Group, located southeast from the study area.

Women: Regain Your Professional Footing

Covid-19 has upended the traditional balance of work and family, which was never easy to begin with. In this article, Elizabeth Bagnall and Susan Laverick of Beaufort Group Consulting show how to reclaim personal boundaries and move forward.

Geomorphology of the upper Mkhomazi River basin, KwaZulu-Natal, South Africa, with emphasis on late Pleistocene colluvial deposits

ABSTRACT We present a 1:50 000 scale geomorphological map of the upper Mkhomazi River basin, located in the foothills of the Drakensberg mountains in KwaZulu-Natal Province, South Africa. The sub-horizontal strata of the Permo-Triassic Beaufort Group forms plateau interfluves with a concave valley slope morphology. Locally, thick sequences of late Pleistocene colluvial deposits and associated buried paleosols (Masotcheni Formation) infill first-order tributary stream valleys and extend across the adjacent lower slopes. Surface runoff processes preferentially incise into the poorly consolidated, highly erodible sediments causing severe gully erosion that is responsible for widespread land degradation and desertification phenomena. The main purpose of this work is to derive a geomorphological map of the study area focussing on the erosional landforms to understand their spatial distribution and their relation to the colluvial deposits. Finally, a local and regional stratigraphic correlation of colluvial deposits and associated buried palaeosol profiles is proposed.

Calcic Vertisols in the upper Daptocephalus Assemblage Zone, Balfour Formation, Karoo Basin, South Africa: Implications for Late Permian Climate

ABSTRACT The fully continental succession of the Beaufort Group, Karoo Basin, South Africa, has been used in the development of environmental models proposed for the interval that spans the contact between the Daptocephalus to Lystrosaurus Assemblage Zones, associated by some workers with the end-Permian extinction event. An aridification trend is widely accepted, yet geochemical data indicate that the majority of in situ paleosols encountered in this interval developed in waterlogged environments. To date, the presence of calcic paleosols in the latest Permian can be inferred only from the presence of calcite-cemented pedogenic nodules concentrated in fluvial channel-lag deposits. Here, we report on the first empirical evidence of in situ calcic Vertisols found in the upper Daptocephalus Assemblage Zone near Old Wapadsberg Pass, one of eight classic localities in which the vertebrate turnover is reported in the Karoo Basin. Seven discrete intervals of calcic Vertisols, exposed over a very limited lateral extent, occur in an ∼ 25 m stratigraphic interval. Estimates of mean annual temperature and mean annual precipitation are calculated from geochemical measurements of one paleosol, and these estimates indicate that the prevailing climate at the time of pedogenesis was seasonally cold and humid. Correlation with adjacent stratigraphic sections indicates that the late Permian landscape experienced poorly drained and better-drained phases, interpreted to reflect a climate that varied between episodically dry and episodically wet. In contrast to a paleoenvironmental reconstruction of unidirectional aridification from strata in the Wapadsberg Pass region, this study provides new evidence for a wetting trend towards the Daptocephalus–Lystrosaurus Assemblage-Zone boundary.

Biostratigraphy of the Tapinocephalus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

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.

Biostratigraphy of the Cynognathus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

Abstract The Cynognathus Assemblage Zone is the youngest tetrapod biozone of the Beaufort Group (Tarkastad Subgroup, Karoo Supergroup). It is situated between the underlying Lystrosaurus declivis Assemblage Zone and the base of the overlying Molteno Formation (Stormberg Group) and corresponds to the entire Burgersdorp Formation. It is characterised by the presence throughout of the cynodont genus Cynognathus. The biozone reaches a maximum thickness of around 650 m in the southeast part of the basin and thins dramatically to the north, where it is only a maximum of 50 m thick. We here propose a three-fold subdivision into a lower Langbergia-Garjainia Subzone, a middle Trirachodon-Kannemeyeria Subzone and an upper Cricodon-Ufudocyclops Subzone. The basal contact is defined biostratigraphically by the first appearance of Cynognathus crateronotus and Langbergia modisei. The Cynognathus Assemblage Zone lacks a defined biostratigraphic upper limit, being unconformably terminated by the base of the overlying Molteno Formation, which lacks a terrestrial vertebrate fossil record other than trackways.

Biostratigraphy of the Endothiodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

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.

Biostratigraphy of the Eodicynodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

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.

Discussion of “Permian—Triassic vertebrate footprints from South Africa: Ichnotaxonomy, producers and biostratigraphy through two major faunal crises” by Marchetti, L., Klein, H., Buchwitz, M., Ronchi, A., Smith, R.M.H., DeKlerk, W.J., Sciscio, L., and Groenewald, G.H. (2019)

A newly devised tripartite subdivision of the Karoo Basin, South Africa, is based on a number of vertebrate-trackways spanning the Middle Permian (Wordian/Capitanian) to Lower Triassic (reportedly Induan) rocks of the Beaufort Formation. The youngest Footprint Assemblage (FA III) is reported to occur in the lowermost Triassic rocks of the Palingkloof Member. One collection site from which seven trackways are reported, Bethel farm, is a classic South African locality where some authors place the end-Permian extinction event and, coincidentally, the vertebrate-based terrestrial Permian—Triassic Boundary. Published GPS coordinates for the Bethel farm site, though, indicate that these trackways originate from exposures of the Burgersdorp Formation near the town of Aliwal North. Outcrops here are assigned to the Cynognathus Assemblage Zone, and indicate a Middle Triassic age assignment. In addition, we caution the use of any small temporally or spatially restricted dataset, which is of severely limited utility, in making broad generalizations about paleoenvironmental or paleoecological interpretations.

Case study: methane gas in a groundwater system located in a dolerite ring structure in the Karoo Basin; South Africa

Abstract In the past few years numerous assumptions were made on groundwater in the Karoo Basin and related shale gas development, but not many baseline studies were conducted on groundwater and on boreholes where methane currently occurs. This article focuses on one of these boreholes (BHA) in the Ubuntu Local Municipality area, located close to a dolerite ring structure, which is releasing methane gas. Water samples were analysed for macro and trace elements, environmental isotopes and methane concentrations. Chemical analyses results indicate that groundwater at this borehole may be a mixture between deep groundwater, shallow groundwater and meteoric water. A rise in the groundwater level and subsequent flowing artesian conditions that was observed, support the theory that mixing between deeper groundwater from the Ecca Group and shallower water from the Beaufort Group is taking place. These water level reactions could be due to possible seismic activity within close proximity to the dolerite ring structure and/or due to recharge and interflow to BHA.

The last chapter of 30 million years of molluscan evolution: Permian non-marine bivalves of the Rio do Rasto Formation, Paraná Basin, Brazil

The last chapter of the evolutionary history of the Permian (Artinskian–Wuchiapingian) endemic bivalves of the Passa Dois Group, Brazil, is depicted. They evolved in a vast, isolated epeiric sea under progressive continentalization. Previously, bivalves that thrived during times of marked non-marine (limnic) conditions have been poorly investigated. Hence, a systematic survey of the bivalves between the Leinzia similis assemblage (Serrinha Member) and the Palaeomutela platinensis assemblage (Morro Pelado Member), Rio do Rasto Formation, is presented. Over two hundred specimens were examined, and three bivalve assemblages were identified: (a) the Terraia decarinata assemblage in the uppermost part of the Serrinha Member, including Relogiincola delicata gen. et sp. nov., Palaeomutela australis sp. nov., and Palaeomutela platinensis (Reed, 1935); (b) the Terraia cf. decarinata assemblage in the transition between the Serrinha and Morro Pelado members, including T. decarinata, and P. platinensis, and (c) the Palaeomutela australis assemblage in the lowermost part of the Morro Pelado Member, also including R. delicata and P. platinensis. The investigated bivalves were recorded above the last occurrences of Terraia altissima (Holdhaus, 1918) and Cowperesia emerita Mendes, 1952 in the Serrinha Member. In the Gai-As Formation, Huab Basin, Namibia, these species are found in well-constrained Wordian–Capitanian strata, suggesting a Capitanian–Wuchiapingian age for the studied assemblages. The Permian cosmopolitan freshwater genus Palaeomutela occurs in all three assemblages and is also found in the lower Beaufort Group (South and Central Africa). Therefore, our record may represent the maximum paleobiogeographic expansion of Palaeomutela in Western Gondwana.

First 3D reconstruction and volumetric body mass estimate of the tapinocephalid dinocephalian Tapinocaninus pamelae (Synapsida: Therapsida)

ABSTRACT Dinocephalians were the earliest large terrestrial tetrapods from Gondwana, making this group crucial in understanding body mass (BM) evolution in basal synapsids, but no detailed weight determinations are available for the clade. Here we present the first BM estimate for a dinocephalian on the basis of the remarkably well preserved and complete skeleton of the basal tapinocephalid Tapinocaninus pamelae from the lowermost Beaufort Group of South Africa. We reconstructed three 3D models of Tapinocaninus using mounted skeletons of the dinocephalians Moschops and Ulemosaurus to reconstruct the missing elements. Applying a density range between 0.9 and 1.15 Kg/1000 cm3 for living tissue to the model we reconstructed an average BM of 892.63 Kg for the taxon. Classic regression formulae, based on humerus and femur circumference, provide higher values of 1694.5 Kg and 2015.8 Kg, with an overestimation of 90% and 126% respectively. The study confirms that volumetric BM estimates are more precise, and are recommended if relatively complete skeletons are available. The ‘intermediate’ posture recognized for Tapinocaninus, more upright with respect to the sprawling condition characterizing sphenacodontid ‘pelycosaurs’, could represent a response to a large BM, which, for the first time in synapsids, reaches weights close to a tonne.

A new kannemeyeriiform dicynodont (Ufudocyclops mukanelai, gen. et sp. nov.) from Subzone C of the Cynognathus Assemblage Zone, Triassic of South Africa, with implications for biostratigraphic correlation with other African Triassic faunas

ABSTRACTA new taxon of kannemeyeriiform dicynodont, Ufudocyclops mukanelai, is described based on a well-preserved skull from Subzone C of the Cynognathus Assemblage Zone, which are the youngest strata (probably Middle Triassic) of the Beaufort Group (uppermost Burgersdorp Formation) in South Africa. Ufudocyclops mukanelai is diagnosed by its autapomorphic intertemporal morphology: the intertemporal bar in this taxon is ‘X’-shaped—broad anteriorly and posteriorly but distinctly ‘pinched’ at mid-length and bears a deep, triangular depression immediately behind the enormous pineal foramen. The new kannemeyeriiform can also be diagnosed by the presence of a laterally expanded jugal plate beneath the orbit, and highly discrete, ovoid nasal bosses separated by a broad, unornamented median portion of the premaxilla and the nasals. Two partial dicynodont skulls from this subzone, previously identified as specimens of the otherwise Tanzanian taxon Angonisaurus, are also referable to U. mukanelai. Removal of these specimens from the hypodigm of Angonisaurus eliminates a crucial point of correlation between Cynognathus Subzone C and the Manda Beds of Tanzania and suggests that Subzone C preserves a distinct, endemic fauna, not just a southern extension of the better-known Middle–Late Triassic tetrapod faunas from Tanzania and Zambia. Inclusion of Ufudocyclops in a phylogenetic analysis of anomodonts recovers it as an early stahleckeriid, the first record of this clade from the Cynognathus Assemblage Zone.

The postcranial skeleton of the basal tapinocephalid dinocephalian Tapinocaninus pamelae (Synapsida: Therapsida) from the South African Karoo Supergroup

Dinocephalians form an important component of the Guadalupian basal therapsid faunas of Pangaea. Most research undertaken on this clade has focused on the skull while postcranial research has lagged, largely because of the rarity of sufficiently complete specimens. The discovery of an almost complete skeleton of the basal tapinocephalid dinocephalian Tapinocaninus from the rocks of the lowermost Beaufort Group of South Africa for the first time provides an accurate vertebral count for a dinocephalian as well as morphological information on the appendicular skeleton. The long bones of Tapinocaninus pamelae are autapomorphic in several features within the dinocephalians, and the results enable discussion of some more general aspects of the appendicular skeleton of basal synapsids. Combined, the new data enable a new reconstruction of the posture of tapinocephalids. Although demonstrating several apomorphic characters, the skeleton retains pleisomorphic anatomical features previously known only in pelycosaur-grade synapsids, especially in the axial skeleton. The discovery greatly advances understanding of the postcranial morphology of tapinocephalid dinocephalians and will provide input on the enigmatic phylogenetic relationships of early therapsids.

The first occurrence of Cynognathus crateronotus (Cynodontia: Cynognathia) in Tanzania and Zambia, with implications for the age and biostratigraphic correlation of Triassic strata in southern Pangea

ABSTRACTCynognathus crateronotus is a species of large carnivorous cynodont, first named and best known from the Triassic Burgersdorp Formation (Beaufort Group, Karoo Basin) of South Africa. Fossils of the genus have also been reported from the upper Fremouw Formation of Antarctica, the Upper Omingonde Formation of Namibia, and the Río Seco de la Quebrada Formation of Argentina. Without associated cranial material, however, distinguishing the postcrania of Cynognathus from that of the closely related cynognathian, Diademodon tetragonus, has proven difficult. Here we provide a more comprehensive diagnosis for Cynognathus crateronotus and describe two novel occurrences. First, parts of a medium-sized individual were recovered from a scrambled mass of dental and semiarticulated postcranial material from the lower Ntawere Formation of Zambia, a horizon that previously produced fossils of Diademodon and Kannemeyeria. Second, a large individual was collected from a recently discovered locality within the lower part of the Lifua Member of the Manda Beds of Tanzania. A large proportion of the postcranial skeleton, along with some craniodental remains, was found ex situ in a sandy streambed just downstream from a quarry that has produced the dicynodont Dolichuranus, an azendohsaurid archosauromorph, and the avemetatarsalian Teleocrater rhadinus. The widespread occurrence of Cynognathus across southern Pangea demonstrates its utility as a biostratigraphic marker, but recently published radiometric age estimates from Argentina suggest that either the genus persisted for over 10 million years or African strata traditionally interpreted as Middle Triassic are better understood as Late Triassic in age.Citation for this article: Wynd, B. M., B. R. Peecook, M. R. Whitney, and C. A. Sidor. 2018. The first occurrence of Cynognathus crateronotus (Cynodontia: Cynognathia) in Tanzania and Zambia, with implications for the age and biostratigraphic correlation of Triassic strata in southern Pangea; pp. 228–239 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

A new approach to biostratigraphy in the Karoo retroarc foreland system: Utilising restricted-range palynomorphs and their first appearance datums for correlation

The main Karoo Basin (MKB), internationally renowned for its wealth of fossil tetrapods, has been lithostratigraphically subdivided into three discrete regions: two (east and west) proximal facies adjacent to the Cape Fold Belt, and a distal facies, away from the Cape Fold Belt. Because of lithological differences between formations of the proximal and distal sectors of the MKB, it has been difficult to correlate time-equivalent lithostratigraphic units in the different sectors. Palynology provides a tool for refining stratigraphic correlations within the MKB, but only species with restricted ranges are biostratigraphically significant. Restricted-range palynomorph taxa from the Ecca and Beaufort groups indicate the following relationships: the lowermost Vryheid Formation palynoflora can be strongly correlated with that of the Prince Albert Formation, whereas the Whitehill–Collingham formations and No. 2 seam (Vryheid Formation), and the Ripon Formation and No. 4 seam (Vryheid Formation) can be tentatively linked using palynology. The lower–middle Normandien Formation in the north is chronologically equivalent to the Ripplemead member of the Balfour Formation in the south. Although the Ecca–Beaufort Group boundary is known to be diachronous, restricted-range palynomorphs cannot yet confirm that the uppermost Ecca Group in the northern part of the basin was deposited at the same time as the lower Beaufort Group in the south.This study demonstrates that despite diachronous ranges of some taxa, palynology is useful in correlating age-equivalent lithostratigraphic units in the proximal and distal sectors of the basin. A new First Appearance Datum (FAD) palynozonation for the Karoo is presented that is calibrated by the most recent radiometric dates for South Africa, Australia, and South America. The new zones are also correlated with Permian successions in Antarctica, Zambia, Botswana, and India. Future palynostratigraphic work in South Africa must take into account the ranges and FADs of these palynomorph taxa in order to make meaningful biostratigraphic correlations in the Karoo Basin and across Gondwana.

Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction

Important palaeoenvironmental differences are identified during deposition of the latest Permian Daptocephalus Assemblage Zone (DaAZ) of the South African Beaufort Group (Karoo Supergoup), which is also divided into a Lower and Upper subzone. A lacustrine floodplain facies association showing evidence for higher water tables and subaqueous conditions on the floodplains is present in Lower DaAZ. The change to well-drained floodplain facies association in the Upper DaAZ is coincident with a faunal turnover as evidenced by the last appearance of the dicynodont Dicynodon lacerticeps, the therocephalian Theriognathus microps, the cynodont Procynosuchus delaharpeae, and first appearance of the dicynodont Lystrosaurus maccaigi within the Ripplemead member. Considering the well documented 3-phased extinction of Karoo tetrapods during the Permo-Triassic Mass Extinction (PTME), the facies transition between the Lower and Upper DaAZ represents earlier than previously documented palaeoenvironmental changes associated with the onset of this major global biotic crisis.

U-Pb detrital zircon dates and provenance data from the Beaufort Group (Karoo Supergroup) reflect sedimentary recycling and air-fall tuff deposition in the Permo-Triassic Karoo foreland basin

Detrital zircon U-Pb age dating was used for provenance determination and maximum age of deposition for the Upper Permian (upper Teekloof and Balfour formations) and Lower Triassic (Katberg Formation) lithostratigraphic subdivisions of the Beaufort Group of South Africa's Karoo Basin. Ten samples were analysed using laser ablation - single collector - magnetic sectorfield - inductively coupled plasma - mass spectrometry (LA-SF-ICP-MS). The results reveal a dominant Late Carboniferous-Late Permian population (250 ± 5 Ma – 339 ± 5 Ma), a secondary Cambrian-Neoproterozoic (489 ± 5 Ma to 878 ± 24 Ma) population, a minor Mesoproterozoic (908 ± 24 Ma to 1308 ± 23) population, and minor occurrences of Devonian, Ordovician, Proterozoic and Archean zircon grains. Multiple lines of evidence (e.g. roundness and fragmentary nature of zircons, palaeo-current directions, and previous work), suggest the older zircon populations are related to sedimentary recycling in the Gondwanide Orogeny. The youngest and dominant population contain elongate euhedral grains interpreted to be directly derived from their protolith. Since zircons form in felsic igneous rocks, and no igneous rocks of Late Permian age occur in the Karoo Basin, these findings suggest significant input of volcanic material by ash falls. These results support sedimentological and palaeontological data for a Lopingian (Late Permian) age for the upper Beaufort Group, but contradict previous workers who retrieved Early Triassic dates from zircons in ashes for the Beaufort and Ecca Groups. Pb-loss not revealed by resolvable discordance on the concordia diagram, and metamictization of natural zircons are not factored into the conclusions of earlier workers.

Anatomy and relationships of the South African gorgonopsian Arctops (Therapsida, Theriodontia)

AbstractThe gorgonopsian genus Arctops from the late Permian of South Africa is revised and redescribed. The nominal species Arctops kitchingi and Arctops watsoni are found to be junior synonyms of the type species Arctops willistoni. A well‐prepared specimen previously referred to Lycaenops angusticeps and additional, previously undescribed specimens are also referred to A. willistoni. The vomerine morphology of Arctops is highly distinctive, supporting previous work highlighting the taxonomic importance of this element. Arctops is restricted to the Cistecephalus Assemblage Zone of the South African Beaufort Group. Inclusion of Arctops in a phylogenetic analysis of gorgonopsian relationships recovers it as the sister‐taxon of Smilesaurus ferox, with the clade composed of Arctops + Smilesaurus positioned outside the Rubidgeinae.