Karoo Basin Research Articles

New material of Dicynodon angielczyki (Synapsida: Anomodontia) from Mozambique and Zambia with biostratigraphic implications for African Permo-Triassic basins

ABSTRACT Dicynodont therapsids are widely used in Permo-Triassic vertebrate biostratigraphy. However, recent taxonomic revisions have left few valid species with broad enough geographic distributions to use in establishing interbasinal correlations; instead, most currently recognized dicynodont species are basinal endemics. This is particularly true of the array of Permian dicynodontoids held in the formerly cosmopolitan wastebasket genus Dicynodon, now considered to mostly represent distinct (and in many cases distantly related) local taxa. As an example, Dicynodon fossils from the Ruhuhu Basin of Tanzania, formerly referred to “Dicynodon huenei,” have recently been separated out as a distinct species, Dicynodon angielczyki. Dicynodon angielczyki has been considered a Ruhuhu Basin endemic, as no records of this taxon are known in the extensive dicynodont sample from the Karoo Basin of South Africa. However, there has been little research on dicynodontoids from other upper Permian basins in eastern Africa, and their taxonomic composition is uncertain. Here, we describe the first specimens referable to D. angielczyki from other African sedimentary basins, demonstrating that this species is also present in the Metangula Graben of Mozambique and Luangwa Basin of Zambia. The new specimens permit improved correlations between the rock units of these basins as well as providing new information on the anatomy and possibly ontogeny of D. angielczyki.

Stepping out across the Karoo retro-foreland basin: Improved constraints on the Ecca-Beaufort shoreline along the northern margin

The Karoo Supergroup of South Africa, internationally renowned for its almost continuous Carboniferous to Jurassic record of deposition in a foreland basin setting, hosts an unparalleled record of fossil tetrapods that provides unique insight into terrestrial biodiversity change over this extended period. Understanding of the litho-, bio- and chronostratigraphy of the Karoo Basin has greatly improved in recent years but most work has focused on the thicker and better-exposed rocks in the basinal foredeep. A core issue that has remained ambiguous is the stratigraphic placement of the diachronous Ecca-Beaufort contact, for which different criteria have been used during mapping in different parts of the main Karoo Basin. Comparison of biostratigraphy and contrasting lithological facies changes with those in the better-studied foredeep enabled us to revise the lithostratigraphy of the Ecca and Beaufort groups in the distal part of the main Karoo Basin. The presence of proximal marine facies associations in the distal sector conform with the definition of the Waterford Formation of the Ecca Group, so far recognised only in the southern foredeep. The upper contact of the Waterford Formation represents a change from a subaqueous to a subaerial delta plain depositional environment and marks the boundary between the Ecca and Beaufort groups, as in the south. This has consequences for Beaufort Group stratigraphic subdivision in the distal sector of the Karoo foreland basin.

Mesosaur taxonomy reappraisal: are Stereosternum and Brazilosaurus valid taxa?

Mesosaurs are basal amniotes that lived at the beginning of the Permian or close to the Permo–Carboniferous boundary. Despite the several hundred specimens that have been found, including complete skeletons of adult and juvenile individuals, mesosaur taxonomy has been subjected to a high controversy over time. Currently, three monotypic genera, Mesosaurus tenuidens Gervais, Stereosternum tumidum Cope, and Brazilosaurus sanpauloensis Shikama & Ozaki are recognized, but identification of new specimens using the available diagnostic characters are arbitrary and influenced by high subjectivity. We performed anatomical and morphometric analyses to look for statistical support to these previously suggested basic diagnostic characters through an exhaustive anatomical revision of these characters and also of some new attributes discovered during the course of our study. We found a notable influence of taphonomic features in most of the diagnostic characters used to differentiate the three monotypic genera, including strong bias derived from the preservation of individuals in different ontogenetic stages, whose size and degree of ossification could have been controlled by particular environmental conditions that resulted in subtle polymorphisms of these and other few characters. Other features may even represent sexual dimorphism. After the detailed revision of the type specimens of the three currently accepted mesosaur taxa, for which we include here good-quality photographs, and considering the lack of statistical support for the most applied putative diagnostic features such as the different ratio found when comparing skull and cervical region lengths and the low or higher intensity of pachyosteosclerosis observed in dorsal ribs, which can be controlled by taphonomic and ecological conditions, we recognize Mesosaurus as the only mesosaurid taxon in the Paraná and Karoo basins, probably including dwarf individuals. Therefore, S.tumidum and B. sanpauloensis are suggested here as nomina dubia taking into account that the autapomorphies that supported these taxa cannot be confirmed to be absent in Mesosaurus. Keywords: Mesosaurus, morphometrics, taxonomy, ?Early Permian, Gondwana.

Geochemical and petrographic characteristics of sediments along the transboundary (Kenya–Tanzania) Umba River as indicators of provenance and weathering

Abstract The Umba River basin is one of the smaller-scale hydrological basins in the East African region. It traverses two countries, with its catchment in the Usambara mountains in Tanzania, while it drains its waters to the Indian Ocean in Vanga, Kenya. The chemical and mineralogical compositions of the riverbank and bottom sediments of the Umba River were analyzed and evaluated to describe their source characteristics and provenance. The dominant minerals include quartz, K-feldspars, plagioclase, hornblende, pyroxenes, muscovite, biotite, and likely presence of clays such as kaolinite. The chemical index of alteration of the sediments indicate a moderate to high degree of alteration. They reflect a dominant mafic to intermediate igneous provenance consistent with the geology of the Umba River catchment that is characterized by the outcrops of the granitic Precambrian basement and the quartz-dominated Paleozoic Karoo Supergroup, overlain by Mesozoic and Cenozoic sediments dominated by both mafic and felsic minerals. The similarity of the chemical and mineralogical compositions of the Umba River sediments from source to mouth further indicates a uniform source in the upper course of the river and only subordinate contributions from the lower course where it passes the Karoo and the younger sediments.

The Origin and 3D Architecture of a Km-Scale Deep-Water Scour-Fill: Example From the Skoorsteenberg Fm, Karoo Basin, South Africa

Scours, and scour fields, are common features on the modern seafloor of deep-marine systems, particularly downstream of submarine channels, and in channel-lobe-transition-zones. High-resolution images of the seafloor have improved the documentation of the large scale, coalescence, and distribution of these scours in deep-marine systems. However, their scale and high aspect ratio mean they can be challenging to identify in outcrop. Here, we document a large-scale, composite erosion surface from the exhumed deep-marine stratigraphy of Unit 5 from the Permian Karoo Basin succession in South Africa, which is interpreted to be present at the end of a submarine channel. This study utilizes 24 sedimentary logs, 2 cored boreholes, and extensive palaeocurrent and thickness data across a 126 km2 study area. Sedimentary facies analysis, thickness variations and correlation panels allowed identification of a lower heterolithic-dominated part (up to 70 m thick) and an upper sandstone-dominated part (10–40 m thick) separated by an extensive erosion surface. The lower part comprises heterolithics with abundant current and sinusoidal ripples, which due to palaeocurrents, thickness trends and adjacent depositional environments is interpreted as the aggradational lobe complex fringes. The base of the upper part comprises 2-3 medium-bedded sandstone beds interpreted as precursor lobes cut by a 3–4 km wide, 1–2 km long, and up to 28 m deep, high aspect ratio (1:100) composite scour surface. The abrupt change from heterolithics to thick-bedded sandstones marks the establishment of a new sediment delivery system, which may have been triggered by an updip channel avulsion. The composite scour and subsequent sandstone fill support a change from erosion- and bypass-dominated flows to depositional flows, which might reflect increasingly sand-rich flows as a new sediment route matured. This study provides a unique outcrop example with 3D stratigraphic control of the record of a new sediment conduit, and development and fill of a large-scale composite scour surface at a channel mouth transition zone, providing a rare insight into how scours imaged on seafloor data can be filled and preserved in the rock record.

Inter-element variation in the bone histology ofAnteosaurus(Dinocephalia, Anteosauridae) from theTapinocephalusAssemblage Zone of the Karoo Basin of South Africa

Despite its abundance in the Permian fossil record of South Africa, little is known about the life history of Anteosaurus. Here we examine the bone microstructure of multiple skeletal elements of Anteosaurus from the Tapinocephalus Assemblage Zone of the Karoo Basin. The bone histology of Anteosaurus magnificus reveals that the cortex is composed of highly vascularized, uninterrupted fibrolamellar bone tissue surrounding the inner spongy medullary region. However, the histology of two ribs and a previously described femur of another Anteosaurus taxon revealed an interrupted growth pattern with lines of arrested growth and peripheral rest lines occurring in the compacta, indicating periodic pauses in growth possibly linked to the slowing down of growth during maturity. Given that the fibula of the same individual has well-vascularised fibrolamellar bone tissue without any growth marks in the cortex; this suggests variation in skeletal growth. Based on our histological results, three growth dynamic stages are deduced for the genus Anteosaurus: (i) the earliest growth stage is represented by the predominance of highly vascularized, uninterrupted fibrolamellar bone tissue in the inner cortex, which suggests rapid periosteal bone deposition during early ontogeny; (ii) the next stage of growth shows periodic interruptions in the bone deposition as indicated by the deposition of lines of arrested growth; (iii) the third stage shows the development of lamellar bone tissue with rest lines in the peripheral part of the cortex suggesting a slowing down of growth prior to death. Most of the skeletal elements are characterized by thick bone walls, extensive secondary reconstruction and the complete infilling of the medullary cavity. However, the radius and a previously studied femur have open medullary cavities with struts of bony trabeculae. Based on histologic structures and comparisons with extant taxa, it is likely that Anteosaurus may have been more terrestrial as its osteology point towards terrestriality, but it may have occasionally inhabited ephemeral pools like modern semi-aquatic Hippopotamus.

Bipedal leaping Jurassic vertebrates in Southern Africa: proposed new ichnotaxon and inferred palaeoenvironment

The Lower Jurassic Clarens Formation (Stormberg Group, Karoo Supergroup, Main Karoo basin) contains relatively common vertebrate trackways impressed into apparently soft to firm, fine sediment beds preserved within the succession. At least three known ichnotaxa are interpreted as leaping bipedal vertebrates. Here we provide a generic description of a proposed new ichnotaxon to add to this small group of the oldest known bipedal hopping vertebrates in Africa and globally. Saltirecarpipes Genus Nova (Type Species tinleyi) (saltus – leap; carpe – seize; pes – foot) has been identified from tracks at Giants Castle in the KwaZulu-Natal Drakensberg. The type specimen in the National Museum Bloemfontein exhibits two adjacent tetradactyl impressions with four digits extended from metatarsal pads, comprising three inner digits grouped closer together and facing forwards, the fourth digit being much longer and curved outwards and slightly backwards. The digits are all strongly curved with claw impressions being preserved in several cases. These were small vertebrates, a leap length of ca. 180 mm being inferred. Being found in association with trace fossils of Equisitales (horse tails) a wet palaeoenvironment of small ponds is postulated. These appear to have been associated with distal fan sheetflood deposits of fine sediment at Giants Castle, which pass laterally into more central-basinal palaeodune deposits which characterise the Clarens Formation across the Main Karoo depository. The new ichnotaxon appears to have been restricted to wet desert marginal settings, feeding immature sediment to the desert basin, and which retreated proximally as aridification of the Clarens palaeoenvironment progressed.

Application of ground magnetic and soil geochemical surveys for mapping potential kimberlite bodies in the southern margin of the Archaean Kaapvaal Craton, South Africa

In this study, the southern margin of the Archean Kaapvaal Craton in South Africa is selected to investigate the occurrences of potential kimberlite bodies. Ground magnetic survey was conducted to identify potential targets for further exploration. Euler 3D deconvolution and Keating correlation coefficients are the processing techniques that were applied to the ground magnetic data to identify geological features that correspond to kimberlite models. These techniques revealed several potential targets that resemble geologic models of kimberlite bodies. Seven of these targets (Targets A, B, C, D, E, F and G), spatially cluster along or at the intersections of linear structures, which is consistent with one of the primary geological conditions that control the emplacement of kimberlite bodies. A follow-up soil sampling and analysis was conducted to assess the geochemistry of soils at the seven targets. The major element geochemistry of soil samples suggest that Target B possesses residual soils that originated from kimberlite intrusion, while the remaining six samples show geochemical characteristics of soils derived from crustal rocks. The composition of compatible (Ni, Cr, V, Co, Cu and Zn) and incompatible (Nb, Zr, Sr, Ce, and Ba) trace elements of Target B shows similarity with the known Group 1 Kimberlites locally and globally, thus confirming that Target B most probably belongs to Group 1 Kimberlite petrological clan. This, however, does not preclude the possibility of modification of kimberlite chemistry by crustal assimilation during ascent and post-emplacement processes such as weathering as demonstrated by elevated concentrations of SiO2, Al2O3 and Rb and low content of MgO. In light of this, Target B may be interpreted as a potentially contaminated and weathered Group 1 Kimberlite pipe which intruded the Karoo Supergroup at the intersection of linear structures. This finding is consistent with the presence of large number of known diamondiferous kimberlites in this region, which post-date the formation of the Karoo Supergroup.

Sedimentary facies, stratigraphy, and depositional environments of the Ecca Group, Karoo Supergroup in the Eastern Cape Province of South Africa

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.

E&P Notes (July 2021)

E&P Notes (July 2021)

A tale of two Tweefonteins: What physical correlation, geochronology, magnetic polarity stratigraphy, and palynology reveal about the end-Permian terrestrial extinction paradigm in South Africa

Abstract The contact between the Daptocephalus to Lystrosaurus declivis (previously Lystrosaurus) Assemblage Zones (AZs) described from continental deposits of the Karoo Basin was commonly interpreted to represent an extinction crisis associated with the end-Permian mass-extinction event at ca. 251.901 ± 0.024 Ma. This terrestrial extinction model is based on several sections in the Eastern Cape and Free State Provinces of South Africa. Here, new stratigraphic and paleontologic data are presented for the Eastern Cape Province, in geochronologic and magnetostratigraphic context, wherein lithologic and biologic changes are assessed over a physically correlated stratigraphy exceeding 4.5 km in distance. Spatial variation in lithofacies demonstrates the gradational nature of lithostratigraphic boundaries and depositional trends. This pattern is mimicked by the distribution of vertebrates assigned to the Daptocephalus and L. declivis AZs where diagnostic taxa of each co-occur as lateral equivalents in landscapes dominated by a Glossopteris flora. High-precision U-Pb zircon (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) age results indicate maximum Changhsingian depositional dates that can be used as approximate tie points in our stratigraphic framework, which is supported by a magnetic polarity stratigraphy. The coeval nature of diagnostic pre- and post-extinction vertebrate taxa demonstrates that the L. declivis AZ did not replace the Daptocephalus AZ stratigraphically, that a biotic crisis and turnover likely is absent, and a reevaluation is required for the utilization of these biozones here and globally. Based on our data set, we propose a multidisciplinary approach to correlate the classic Upper Permian localities of the Eastern Cape Province with the Free State Province localities, which demonstrates their time-transgressive nature.

Geomechanical properties of the Permian black shales in the southern main Karoo Basin: lessons from compositional and petrophysical studies

AbstractPermian black shales from the lower Ecca Group of the southern main Karoo Basin (MKB) have a total organic carbon (TOC) of up to ~5 wt% and have been considered primary targets for a potential shale gas exploration in South Africa. This study investigates the influence of shale composition, porosity, pressure (P) and temperatures (T) on their geomechanical properties such as compressive strength and elastic moduli. On average, these lower Ecca Group shales contain a high proportion, ~50 to 70 vol%, of mechanically strong minerals (e.g., quartz, feldspar, pyrite), ~30 to 50 vol% of weak minerals (e.g., clay minerals, organic matter) and ~0 to 50 vol% of intermediate minerals (e.g., carbonates), which have highly variable mechanical strength. Constant strain rate, triaxial deformation tests (at T ≤100°C; P ≤50 MPa) were performed using a Paterson-type high pressure instrument. Results showed that the Prince Albert Formation is the strongest and most brittle unit in the lower Ecca Group in the southern MKB followed by the Collingham and then the Whitehill Formation. Compressive strength and Young’s moduli (E) increase with increasing hard mineral content and decrease with increasing mechanically weak minerals and porosity. On comparison with some international shales, for which compositional and geomechanical data were measured using similar techniques, the lower Ecca Group shales are found to be geomechanically stronger and more brittle. This research provides the foundation for future geomechanical and petrophysical investigations of these Permian Ecca black shales and their assessment as potential unconventional hydrocarbon reservoirs in the MKB.

Palaeo-environmental and provenance reconstruction of the Lower Permian mudstones (lower Ecca Group) in the main Karoo Basin, South Africa

Assessing the composition and origin of the organic matter-rich mudstones, which dominate the early basin fill of the main Karoo Basin of South Africa, are essential for reconstructing the palaeo-environment, palaeo-climate, and potential provenance areas in southern Gondwana during the Early Permian. This study investigates the sedimentary geochemistry and petrography (e.g., major oxides, trace elements, mineral compositions, sedimentary structures, textures) of the lower Ecca Group, which was sampled in newly drilled boreholes. Our results show that the rate of weathering decreased over time as the environment changed from an ice-house to a more hot-house setting (i.e., the Chemical Index Alteration is 72–85 in the Prince Albert Formation and 60–76 in the Collingham Formation). Comparisons of the V/Cr, V(V + Ni), and Ni/Co ratios and Fe–S-TOC ternary plot show oscillations between anoxic and oxic conditions during deposition. Furthermore, there is evidence, albeit somewhat equivocal, for changing palaeo-salinity levels, low sedimentation rates, and high bio-productivity. Trace-element Principal Component Analysis, the Index of Compositional Variability, and Discriminant Function Analysis of the older mudstones (Prince Albert and Whitehill formations) imply different provenance regions with felsic to intermediate signatures predominantly found in the western MKB and mafic signatures in the eastern MKB. The youngest unit, the Collingham Formation, has a more uniform composition across the region, and was mostly sourced from the quartz-arenites and granites most likely associated with the Cape Fold Belt.

New data on the Triassic temnospondyls from the Karoo rift basins of Tanzania and Zambia

Temnospondyl specimens collected recently in the Middle-?Late Triassic of the Ruhuhu (Tanzania) and Luangwa (Zambia) rift basins are described and figured. They are attributed to cf. Cherninia megarhina (Chernin & Cosgriff, 1975), Mastodonsauroidea indet., Stereospondyli indet., and cf. Stereospondyli, as well as intercentra of small adult individual(s) which may belong to a new taxon. Although fragmentary, this new material allows taxonomic updates to the Triassic temnospondyl assemblages of Tanzania and Zambia and documents an interesting phylogenetic and ecological diversity. For example, among the Triassic mastodonsauroids of Zambia, Cherninia megarhina coexisted with Stanocephalosaurus pronus (Howie, 1970) in nonmarine environments. Similar to that of the South African Karoo Basin, these temnospondyl assemblages also illustrate the rapid recovery of the group after the Permian-Triassic mass extinction and contribute to a better understanding of the impact of this extinction on the tetrapod faunas of southern Pangea.

Seismic imaging of dolerite sills and volcanic vents in the Central Karoo, South Africa: implications for shale gas potential

Abstract The Karoo Basin of South Africa covers an area of 700 000 km2 and has been identified as a possible shale gas reserve. Any evaluation of the shale gas potential of the basin must consider the widespread dolerite dykes and sills. These intrusions were emplaced into the Karoo Supergroup and are well dated at around 183 Ma. Their intrusion triggered the explosive releases of gas in the basin, marked on surface by breccia pipes and hydrothermal vents. This outpouring of gas has been proposed as a significant contributor to global climate change. Research into the three-dimensional interconnected structure of these dolerite sills and dykes and their interaction with the hydrocarbon rich layers in the lower part of the Karoo Supergroup has been limited to localized observations of outcrop, magnetic data, legacy seismic data (from the 1970s) and well core. Here we present an interpreted 65 km long higher-resolution 2D seismic reflection profile across the Karoo Basin, approximately 100 km southeast of Trompsburg. These data were collected in the 1990s and at the time deeper structures along the line interpreted. In this study we focus on the top 0.6 to 2 seconds TWT of the data. The seismic line images the interconnected and cross cutting nature of the dolerite dykes and sills along the profile. We also report possible evidence of a gas escape structure (approximately 2.5 km in diameter at surface) emerging near the edge of a dolerite sill in close proximity to the Whitehill Formation, which is the main target for shale gas exploration. This suggests that gas vents in the eastern Karoo Basin close to Lesotho are due to the release of gas from the carbonaceous shales of the Ecca Group. This is similar to breccia pipes mapped on surface in the western part of the Karoo Basin. This seismic section highlights why dolerite sills and dykes must be considered when evaluating the shale gas potential of the Karoo Basin. We propose that better characterization of the Karoo Basin subsurface by seismic and magnetic studies is necessary prior to any efforts to calculate shale gas reserves.

New Specimen of the Enigmatic Dicynodont Lanthanostegus mohoii (Therapsida, Anomodontia) from the Southwestern Karoo Basin of South Africa, and its Implications for Middle Permian Biostratigraphy

Lanthanostegus is an unusual dicynodont known from only two partial skulls from a single locality near Jansenville in the Eastern Cape Province of South Africa. Although these specimens can be constrained to near the base of the late middle Permian (Guadalupian) Abrahamskraal Formation, their precise age is uncertain as a result of diachroneity of the base of the Formation and the absence, in the Jansenville area, of index taxa to correlate this horizon with the biostratigraphy established in the Western Cape Province. Here, we describe a third skull that we identify as Lanthanostegus, which we recently discovered from a locality north of Laingsburg, on the western side of the main Karoo Basin. This skull reveals morphological details of the palate, occiput, and lower jaw that are not preserved in the described specimens of Lanthanostegus mohoii and will advance understanding of this poorly known dicynodont. This discovery provides the first direct correlation between the lower Abrahamskraal Formation at Jansenville on the eastern side of the basin and the southwestern part of the basin, and suggests that Lanthanostegus occurs in the lowest Tapinocephalus Assemblage Zone (AZ), or possibly to a new assemblage transitional between the Eodicynodon and Tapinocephalus AZs. This supports earlier work proposing that the Eodicynodon AZ is present only on the western side of the Karoo Basin and that the transition from a marine to continental depositional environment occurred later toward the East.

Darting towards Storm Shelter: A minute dinosaur trackway from southern Africa

Theropod dinosaurs are considered the main terrestrial carnivores in the Jurassic and Cretaceous. Their rise to dominance has been linked to, among others, body size changes in their early history, especially across the Triassic–Jurassic boundary. However, to qualitatively assess such temporal trends, robust skeletal and trace fossil data sets are needed globally. The richly fossiliferous southern African continental rock record in the main Karoo Basin offers an unparalleled perspective for such investigations. Herein, by documenting a newly discovered Early Jurassic trackway of very small, functionally tridactyl tracks near Storm Shelter (Eastern Cape) in South Africa, the track record can be expanded. Based on ichnological measurements at the ichnosite and digital 3D models, the footprint dimensions (length, width, splay), locomotor parameters (step length, stride, speed), and body size estimates of the trackmaker are presented. In comparison to other similar tracks, these footprints are not only the smallest Grallator-like tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date. The tracks also show that the small-bodied bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km/h. During the dash, either as a predator or as a prey, the trackmaker’s small feet sunk hallux-deep into the sediment. The tracking surface is overgrown by fossilised microbial mats, which likely enhanced the footprint preservation. Based on track morphometrics and the regional dinosaur skeletal record, the trackmakers are attributed to Megapnosaurus rhodesiensis (formerly Syntarsus rhodesiensis), a small-to-medium-sized, early theropod common in southern Africa.Significance:
 
 A newly discovered Early Jurassic theropod trackway in South Africa contains not only the smallest tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date.
 The tracks show that the small bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km per hour.
 During the run, the trackmaker’s feet sunk so deeply into the sediment that even the forwards-directed halluces were impressed.
 
 Open data set: https://doi.org/10.6084/m9.figshare.13007240.v1

Latest Permian insects from Wapadsberg Pass, southern Karoo Basin, South Africa

AbstractThe Permian–Triassic global crisis was the only event to have a dramatic impact on insect diversity, with Palaeozoic insect clades disappearing and accompanied by the accelerated rise of modern lineages. To date, most Permian palaeoentomological work has focused on the upper Permian deposits of the Normandien Formation (Beaufort Group), KwaZulu–Natal Province. This paper describes the regional insect fauna preserved close to the Permian–Triassic boundary at Wapadsberg Pass, southern Karoo Basin of South Africa, which provides a rare glimpse into insect life immediately before this global crisis. Here, we describe six insect species from six families within five orders from the two Wapadsberg Pass localities. Mioloptera stuckenbergi (Grylloblattodea) and Permocicada sp. (Hemiptera) were recorded previously from the Lopingian KwaZulu–Natal Province. In addition, we detail the first potential occurrence of South African Permian Tettigoniida (Orthoptera: Tettigonioidea & Hagloidea) and Anthracoptilidae (Paoliida). An Auchenorrhynchan (Hemiptera) nymph and an undetermined insect (order uncertain) also are described.

Karoo lava-fed deltas and a petrified forest from the Lower Jurassic of southern Gondwana

Palaeoenvironmental changes during continental flood basalt volcanism in large igneous provinces are increasingly linked to global environmental perturbations. Whilst the geology of the Karoo-Ferrar continental flood basalts, including their eruption history, mode of emplacement, timing, geochemistry, palaeomagnetism, has been described, and the causal link of this massive volcanic event to global climate trends and the mass extinction as well as oceanic anoxia near the Pliensbachian–Toarcian boundary is established, little is known about the dynamics of the southern African palaeoenvironment and palaeoclimate at that time. This study is focused on a field investigation of the uppermost Karoo Supergroup, which accumulated in the changing Early Jurassic palaeo-landscapes of southern Gondwana. Using well-exposed successions in southwestern Lesotho, we document evidence of a humid phase at the onset of Karoo volcanism in the central part of the main Karoo Basin. The studied interval encompasses the conformable contact of the Sinemurian–Pliensbachian Clarens Formation and the Pliensbachian–Toarcian flood basalts in the lower Drakensberg Group. Facies changes in the succession provide evidence for shifts in the ancient landscape and in the associated subaerial and subaqueous conditions. Specifically, the facies suggest a climatic change from a dry desert setting with large, down-wind migrating sand dunes to a wetter desert ecosystem in the Late Pliensbachian. The latter sustained a fairly diverse biota of land-dwelling organisms, which included herbaceous and wooded areas where the diametre of gymnospermous tree trunks was in excess of 50 cm. The earliest flood basalts comprise massive basalt lava flows and up to ~10-m-thick foreset-bedded pillow lavas. These show that during the initial outpouring of the Karoo continental flood basalts, the land surface was locally covered by streams and lakes into which the earliest basaltic lavas flowed forming lava-fed deltas in the Late Pliensbachian.

Shear wave splitting measurements in northeastern Uganda and southeastern Tanzania: corroborating evidence for sublithospheric mantle flow beneath East Africa

SUMMARY Several interpretations of shear wave splitting measurements in East Africa have been proposed, but a comprehensive understanding of seismic anisotropy is lacking vis-à-vis geodynamic processes affecting the African Plate, in part because of geographically limited data coverage. Here, we report new shear wave splitting observations using PKS, SKS and SKKS phases recorded on 17 temporary AfricaArray seismic stations in northeastern Uganda and southeastern Tanzania that help fill key gaps in data coverage in non-volcanic regions of East Africa. The stations in northeastern Uganda straddle the Aswa shear zone, which separates the Neoproterozoic Saharan Metacraton (to the east) and the Palaeoproterozoic Northern Uganda Terrane (to the west). The stations in southeastern Tanzania are located mostly in Karoo basins formed within the Neoproterozoic Mozambique Belt. Our results show NNE fast polarization directions in northeastern Uganda, with splitting times between 1.0 and 1.5 s, and NE directions in southeastern Tanzania, with splitting times between 0.6 and 1.3 s. The NNE fast polarization directions in Uganda cannot be explained with oriented melt pocket (OMP) anisotropy in the lithosphere, as the stations are far from any volcanic fields, or fossil anisotropy resulting from the Neoproterozoic East African orogeny. They are, however, parallel to the flow direction of the African superplume and corroborate previous measurements from northern Uganda that were used to argue that the overall northerly orientation of fast polarization directions across East Africa can be attributed to sublithospheric mantle flow associated with the African superplume. The NE fast polarization directions in Tanzania cannot be explained with SE-oriented fossil anisotropy expected from the Mesozoic rifting of Madagascar from Africa or OMP anisotropy in the lithosphere. However, they are consistent with the overall northerly orientation of fast polarization directions in East Africa and can be attributed to either fossil anisotropy in the Mozambique Belt lithosphere resulting from the East African Orogeny or sublithospheric mantle flow associated with the African superplume.