Enigmatic trace fossils from the Aeolian lower Jurassic Clarens formation, Southern Africa

The Lower Jurassic aeolienites of the Clarens Formation in southern Africa contain unique sedimentary structures that are unlikely to be non-biogenic. They are also unlike any known modern or ancient trace fossils. Here, some nigmatic, horizontal,regularly-oriented sedimentary structures are described, which occur in association with other trace fossils as well as features that were previously nterpreted as nests of termites or termite-like ancient social nsects. These spectacular structures are exposed in enormous profusion as straight, ~5 mm cylinders with strong compass orientation, in parallel alignment with one another and to ancient horizontal bedding planes. Their fill is identical to that of the host rock: clean, well-sorted, very fine- to finegrained quartz-arenite. In cross-section, each structure is defined by a subtle, ~0.1 mm thin, concentric gap. Without comparable modern biogenic structures, the biological origin of the structures is uncertain. Their strong compass orientations are, however, also inconsistent with an inorganic origin, even though they may resemble pipey concretions generated by flowing groundwater. Nonetheless, this paper, based on spatiotemporal distribution patterns of the oriented structures, their locally high abundance and association with obvious trace fossils, as well as other sedimentological and palaeontological lines of evidence, argues that the compass structures may be products of ancient social invertebrates living in a resource-limited, semi-arid to arid environment. Furthermore, the compass structures as well as the accompanying structures of the predominantly aeolian Clarens Formation collectively imply the recurrence of favourable ecological parameters (e.g., moist ubstrates) related to episodic climate fluctuations in the Early Jurassic of southern Pangaea (i.e., southern Gondwana)

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

Enigmatic trace fossils from the Aeolian lower Jurassic Clarens formation, Southern Africa

The Lower Jurassic aeolienites of the Clarens Formation in southern Africa contain unique sedimentary structures that are unlikely to be non-biogenic. They are also unlike any known modern or ancient trace fossils. Here, some nigmatic, horizontal,regularly-oriented sedimentary structures are described, which occur in association with other trace fossils as well as features that were previously nterpreted as nests of termites or termite-like ancient social nsects. These spectacular structures are exposed in enormous profusion as straight, ~5 mm cylinders with strong compass orientation, in parallel alignment with one another and to ancient horizontal bedding planes. Their fill is identical to that of the host rock: clean, well-sorted, very fine- to finegrained quartz-arenite. In cross-section, each structure is defined by a subtle, ~0.1 mm thin, concentric gap. Without comparable modern biogenic structures, the biological origin of the structures is uncertain. Their strong compass orientations are, however, also inconsistent with an inorganic origin, even though they may resemble pipey concretions generated by flowing groundwater. Nonetheless, this paper, based on spatiotemporal distribution patterns of the oriented structures, their locally high abundance and association with obvious trace fossils, as well as other sedimentological and palaeontological lines of evidence, argues that the compass structures may be products of ancient social invertebrates living in a resource-limited, semi-arid to arid environment. Furthermore, the compass structures as well as the accompanying structures of the predominantly aeolian Clarens Formation collectively imply the recurrence of favourable ecological parameters (e.g., moist ubstrates) related to episodic climate fluctuations in the Early Jurassic of southern Pangaea (i.e., southern Gondwana)

Sedimentology of the upper Karoo fluvial strata in the Tuli Basin, South Africa

The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) may be grouped in four stratigraphic units: the basal, middle and upper units, and the Clarens Formation. This paper presents the findings of the sedimentological investigation of the fluvial terrigenous clastic and chemical deposits of the upper unit. Evidence provided by primary sedimentary structures, palaeontological record, borehole data, palaeo-flow measurements and stratigraphic relations resulted in the palaeo-environmental reconstruction of the upper unit. The dominant facies assemblages are represented by sandstones and finer-grained sediments, which both can be interbedded with subordinate intraformational coarser facies. The facies assemblages of the upper unit are interpreted as deposits of a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the upper unit, the climate was semi-arid with sparse precipitation resulting in high-magnitude, low-frequency devastating flash floods. The current indicators of the palaeo-drainage system suggest flow direction from northwest to southeast, in a dominantly extensional tectonic setting. Based on sedimentologic and biostratigraphic evidence, the upper unit of the Tuli Basin correlates to the Elliot Formation in the main Karoo Basin to the south

Sedimentology of the Karoo Supergroup in the Tuli Basin (Limpompo River area, South Africa)

The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) consist of various terrigenous clastic and chemical deposits (parabreccias, conglo-breccias, conglomerates, sandstones, fine-grained sediments, calcretes and silc~etes). Four stratigraphic units were identified: the Basal, Middle and· Upper Units, and the CI~rens Formation. The palaeo-environmental reconstructions of the four stratigraphic units are based on evidence provided by primary sedimentary structures, palaeo-flow measurements, clast size/shape analysis, petrographic studies, palaeontological findings, borehole data and stratigraphic relations. The facies associations of the Basal Unit are interpreted as colluvial fan and low sinuosity, braid~d river channel with coal-bearing overbank and thaw-lake deposits. The interpreted depositional environment implies a cold climate, non-glacial subarctic fluvio-Iacustrine system. The current indicators of the palaeo-river system suggest flow direction from ENE to WSW. The lithologies of the Basal Unit are very similar to the deposits of the fluvial interval in the Vryheid Formation (Ecca Group) of the main Karoo Basin. There is no indubitable evidence for glacial activity (e.g. striated pavements or clasts, varvites, etc.), therefore the presence of unequivocal Dwyka Group correlatives in the Tuli Basin remains uncertain. The sedimentary structures and palaeo-current analysis indicate that the beds of the Middle Unit were deposited by an ancient river system flowing in a north-northwesterly direction. A lack of good quality exposures did not allow the reconstruction of the fluvial style, but the available data indicate a high-energy, perhaps braided fluvial system. The lack of bio- and chronostr~~igraphic control hampers precise correlation and enables only the lithocorrelation of the Middle Unit with other braided river systems either in the Beaufort Group or in the Molteno Formation of the main Karoo Basin. The depositional environment of the Upper Unit is interpreted as a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the unit, the climate was semi-arid with sparse precipitation resulting -iFlhighmagnitude, low-frequency devastating flash floods. The sediments were built out from a distant northwesterly source to the southeast. The unambiguous correspondence between the Upper Unit and the Elliot Formation (main Karoo Basin) is provided by lithological similarities and prosauropod dinosaurs remains. The palaeo-geographic picture of the Clarens Fonnation indicates a westerly windsdominated erg environment with migrating transverse dune types. The ephemeral stream deposits, fossil wood and trace fossils are only present in the lower part of the Formation, indicating that the wet-desert conditions were progressively replaced by dry-desert conditions. Based on lithological and palaeontological evidence, the Formation correlates with the Clarens Formation in the main Karoo Basin. At this stage, it remains difficult to establish the exact cause of the regional palaeo-slope changes during the deposition of the Karoo Supergroup in the Tuli Basin. It is probable that foreland system tectonics, which affected the lower part of the Supergroup (Basal Unit and Middle Unit?), were replaced by incipient continental extension and rift related tectonic movements in the Middle and Upper Units, and Clarens Formation

Proceedings of the 2nd International Conference of Continental Ichnology (ICCI 2017), Nuy Valley (Western Cape Winelands), 1–8 October 2017

The 2nd International Conference of Continental Ichnology (ICCI 2017) was held in Nuy Valley (Western CapeWinelands) and followed by a field trip across South Africa to Lesotho from 1st to 8th of October 2017. The conference was dedicated to the study of continental trace fossils, and delegates presented research that focused on investigating various ichnofossils such as burrows, nests, tracks and trails. These are important not only for detailed characterization of past depositional environments, recognition of unconformities, prospecting for hydrocarbon resources, and biostratigraphic subdivisions, but also for the direct link they provide to ancient animal behaviour. The conference was organized by Dr Emese M. Bordy and the postgraduate students of her Sedimentology–Palaeontology Group at University of Cape Town (UCT), and was attended by 50 international delegates from Canada, U.S.A., Uruguay, Argentina, France, Germany, Sweden, Switzerland, Russia, Spain, U.K., Italy, Poland, South Africa and Lesotho (Fig. 1). This proceedings volume reflects the calibre and experience of the ICCI 2017 attendees, who appeared to be an ideal mix of senior and junior scientists. One third of the delegates were postgraduate students, and about of quarter of them were international students. We hope that all of you will enjoy the scientific content of this proceedings volume, which, among others, aims to showcase some of the best continental ichnological work globally and demonstrate why southern Africa is not only an exquisite geological and palaeontological wonder but also a world class ichnological research destination. The abundance and often uniqueness of the continental trace fossils in southern Africa are in stark contrast with the slow and punctuated development of ichnology in the region, even though the recognition and utilization of animal traces have been actively practiced here since prehistoric times. Cave paintings from the pre-1800s indicate that the indigenous hunter-gatherer San people, who have legendary neoichnological expertise, developed an early interest in the rich palaeoichnological record of the region and attempted to interpret ancient trace-making organisms (Ellenberger et al. 2005). Fascination with trace fossils and the identification of the producers by layman have also been recorded, among others, in the Western Cape (South Africa), where local farmers interpreted some Ordovician eurypterid tracks as footprints of ancient tortoises (Fig. 2A – Braddy & Almond 1999). The incorrect identification of trace fossils, which seems to be one of the most persistent traits of ichnology, is also associated with the first written record of a southern African trace fossil (later named Plagiogmus, a vermiformmetazoan trace – Fig. 2B) originally reported as impressions of fossil eels by H. Lichtenstein in his diary in 1803 (Macrae 1999; Master 2010). The first published record of invertebrate ichnofossils appeared in press nearly 70 years later as ‘trails of worms and tracks of Crustacea’ found in the Permian Ecca Group on Schietfontein farm (near Carnarvon) (Dunn 1872). Although vertebrate tracks were recorded in southern Africa in the late 19th century (?Dicynodon tracks in South Africa by Holub 1881; bird or lizard trackways in Lesotho by Dieterlen 1885 and Christol 1897), the first mention of invertebrate ichnofossils (Spirophyton) as fairly reliable stratigraphic markers has only been published in southern Africa in the early 20th century (Rogers 1905), after the ‘Age of Fucoids’ and well into the ‘Period of Reaction’ in European history of trace fossil studies. In these early days, Spirophyton was attributed to fucoids (remains of marine algae) or inorganic processes (Rogers 1905; Hatch & Corstorphine 1905) and impressions of seaweed of screw-like form(Schwarz 1912). Its first acceptable interpretation was given almost half of a century later as fossil traces of burrowing worms (Du Toit 1954). Following a slow start, ichnology in southern Africa only developed into an established discipline that links geology, sedimentology and palaeontology during the early 1970s and 1980s. This period is marked by the publication of the first detailed ichnofossil descriptions, ichnotaxonomic treatments and ichnologically based biostratigraphic and palaeoecological reconstructions. This golden era of southern African ichnology is primarily featured in internationally acclaimed contributions by Ann Anderson (Palaeozoic invertebrate ichnofossils, South Africa), Paul Ellenberger (Mesozoic vertebrate tracks, Lesotho), and Gerald Germs (Precambrian and Cambrian invertebrate ichnofossils, Namibia and South Africa). These active years also led to pioneering application of ichnofossils (in conjunction with lithofacies assemblages) to sedimentary facies analysis and interpretation (e.g. palaeobathymetry, marine vs non-marine settings) and incorporation of neoichnological studies in trace fossil interpretations (see works by D.K. Hobday, T.R. Mason, R. Shone, R.M.H. Smith, I.G. Stanistreet, I. Rust, B.R. Turner). The sluggish progress of ichnology in southern Africa, possibly due to geoscientific preoccupation with Karoo vertebrates and economically important Archaean rocks (Mason 1985), appears to be transformed by renewed interest in ichnological research in recent decades. We trust that the transformation has been spurred on by ICCI 2017, which injected even more rigour and enthusiasm into our local research community and offered all attendees opportunities to share and exchange ideas and to foster networking among potential collaborators. Once again, enjoy reading this proceedings volume of Palaeontologia africana! On behalf of the organizing committee: Emese M. BordyPalaeontological Scientific Trust; Geological Society of South Africa; International Association of Sedimentologists; National Research Foundation, South Africa; DST-NRF Centre of Excellence in Palaeosciences; University of Cape Town; Society for Sedimentary GeologyJN

Early Jurassic dinosaur ecosystems in southwestern Gondwana: steps towards refining its palaeoecology

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Quantification of morphological variation in Late Triassic to Early Jurassic theropod tracks of southern Africa

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Swimming and related traces of a Late Triassic freshwater community from the lower Elliot Formation, South Africa

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Possible trace fossils of putative termite origin in the Lower Jurassic (Karoo Supergroup) of South Africa and Lesotho

Complex structures in the sandstones of the Lower Jurassic aeolian Clarens Formation (Karoo Supergroup) are found at numerous localities throughout southern Africa, and can be assigned to five distinct architectural groups: (1) up to 3.3-m high, free-standing, slab-shaped forms of bioturbated sandstones with elliptical bases, orientated buttresses and an interconnecting large burrow system; (2) up to 1.2-m high, free-standing, irregular forms of bioturbated sandstones with 2-cm to 4-cm thick, massive walls, empty chambers and vertical shafts; (3) about 0.15-m to 0.25-m high, mainly bulbous, multiple forms with thin walls (<2 cm), hollow chambers with internal pillars and bridges; (4) about 0.15-m to 0.2-m (maximum 1-m) high, free-standing forms of aggregated solitary spheres associated with massive horizontal, orientated capsules or tubes, and meniscate tubes; and (5) about 5 cmin diameter, ovoid forms with weak internal shelving in a close-fitting cavity. Based on size, wall thickness, orientation and the presence of internal chambers, these complex structures are tentatively interpreted as ichnofossils of an Early Jurassic social organism; the different architectures are reflective of the different behaviours of more than one species, the history of structural change in architectural forms (ontogenetic series) or an architectural adaptation to local palaeoclimatic variability. While exact modern equivalents are unknown, some of these ichnofossils are comparable to nests (or parts of nests) constructed by extant termites, and thus these Jurassic structures are very tentatively interpreted here as having been made by a soil-dwelling social organism, probably of termite origin. This southern African discovery, along with reported Triassic and Jurassic termite ichnofossils from North America, supports previous hypotheses that sociality in insects, particularity in termites, likely evolved prior to the Pangea breakup in the Early Mesozoic