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Large tridactyl dinosaur tracks from the Early Jurassic of southern Gondwana : uppermost Elliot Formation, Upper Moyeni, Lesotho

Abrahams Miengah, Sciscio Lara, Reid Mhairi, Haupt T’nielle, Bordy Emese M.

Annales Societatis Geologorum Poloniae

2020

Vol. 90, No. 1

1--26

A new ichnosite in southwest Lesotho (Upper Moyeni; Quthing District) is located within the uppermost part of the highly fossiliferous Elliot Formation, ~35 m below the conformably overlying Clarens Formation and ~65 m above the world-renowned Lower Moyeni ichnosite. While the Lower Moyeni site preserves diverse Early Jurassic ichnofossils, the ichnites at the Upper Moyeni comprise one vertebrate burrow and ~50 tridactyl tracks with footprint lengths between 15 and 51 cm. Many of the tracks preserve digital pad impressions, claw marks and displacement rims, all related to substrate conditions. The morphometric parameters of the Upper Moyeni tracks are consistent with Grallator, Eubrontes and Kayentapus. Several larger tracks with footprint lengths > 40 cm are Kayentapus-like and Eubrontes-like, and are comparable to previously described very large theropods tracks with lengths > 50 cm from the uppermost Elliot and Clarens formations. On the basis of sedimentological and ichnological evidence, the Upper Moyeni ichnofossils were formed in a palaeolandscape with small rivers and shallow lakes by burrowing tetrapods and a variety of bipedal dinosaurs (theropods), some of which were up to 7–8 m in body length. The Upper Moyeni tracks, together with the other very large tracks from coeval locations in southern Africa, collectively highlight the tendency towards increasing diversity in size of tridactyl tracks and by extension theropod trackmaker body size body size, which runs in tandem with the increasing diversity of non-sauropod, sauropodomorph body fossils in the Sinemurian-Pliensbachian of southern Gondwana.

Dinosaur behaviour in an Early Jurassic palaeoecosystem – uppermost Elliot Formation, Ha Nohana, Lesotho

Rampersadh A., Bordy E. M., Sciscio L., Abrahams M.

Annales Societatis Geologorum Poloniae

2018

Vol. 88, No. 2

163--179

The Ha Nohana palaeosurface in southern Lesotho preserves tridactyl and tetradactyl tracks and trackways attributable to Early Jurassic bipedal, theropod-like dinosaurs. Complementary sedimentological and ichnological observations along the palaeosurface and in the strata below and above it allow detailed interpretations of climatically driven changes in this southern Gondwana palaeoecosystem. Sedimentological evidence suggests trackmaking under a semi-arid climate with heavy storms and episodic flash flooding that induced ephemeral, unconfined sheetwashes. The palaeosurface is overlain by rhythmically bedded, organic-matter rich mudstones that formed in a deep, stratified lake indicative of a longer and wetter period in the history of the site. The unique morphological details of the Ha Nohana tracks help refine the properties of the substrate during track making, the ichnotaxonomic affinities of the footprints and the interpretation of the foot movement relative to the substrate. Two footprint morphotypes, ~ 300 m apart, are defined on the palaeosurface. Tracks of morphotype I are tridactyl, shallow, contain digital pad impressions and were impressed on a firm, sand rippled substrate that underwent desiccation. Conversely, tracks of morphotype II are tetradactyl, deep, and have an elongated posterior region. These tracks are preserved on the surface of a massive sandstone and are associated with soft sediment collapse structures related to the animal’s foot sinking into the water-saturated, malleable sediment layer. Morphotype II tracks show that as the animal waded across the substrate, the liquefied sediment lost its cohesive strength and could only partially support the weight of the animal. In so doing, the animal’s foot sunk deep enough into the sediment such that the impression of the metatarsal and digit I (hallux) are now visible. Thus, the palaeosurface was walked on by small-to-medium sized theropods that traversed over ripple marks in firmer moist sand, as well as a larger theropod that tottered through water-logged sand.

Magnetic and Electromagnetic Signatures around Polile Tshisa Hot Spring in the Northern Neotectonic Belt in the Eastern Cape Province, South Africa

Madi K., Nyabeze P. K., Gwavava O., Sekiba M., Zhao B.

Acta Geophysica

2016

Vol. 64, no. 4

943--962

Finding productive boreholes in the Karoo fractured aquifers has never been an easy task. Fractured Karoo aquifers in the neotectonic zones in the Eastern Cape Province can be targeted for groundwater exploration. The Polile Tshisa hot spring is located in a seismo-tectonic region beset by neotectonics. Hot springs are indicative of circulation of groundwater at great depths along fault zones, and accordingly of neotectonics. The characterisation of hot springs by means of magnetic and electromagnetic methods can help infer the occurrence of structures which are favourable for groundwater potential. The Polile Tshisa hot spring is characterised by faults, fractures, and dolerite dykes. All these structures make the hot spring a good case study for groundwater exploration.