Neogene fluvial deposits along the south-west coast of South Africa understanding the palaeoclimate through proxies

Branched glycerol dialkyl glycerol tetraether (GDGTs) membrane lipids have been used as a new proxy for the reconstruction of terrestrial palaeoclimates. These biomarkers (or molecular ‗fossils‘) in conjunction with palynology, have been effective in the novel analysis of Miocene organic-rich sediments from three South African west coast sites at Rondeberg, Noordhoek and Langebaanweg. Lastly, a Quaternary south coast site at Rietvlei, South Africa, was also studied to further elucidate the extent of use of this new proxy. The fluvial peat and organic-rich deposits of the Elandsfontyn Formation (Sandveld Group) were investigated at Noordhoek, Langebaanweg and Rondeberg to provide new evidence for the climate and vegetation patterns during Miocene in this region. Drill-core and quarry samples from all four sites were freeze-dried, powered, and prepared for biogeochemical and palynological analyses. The methylation index of branched tetraethers (MBT) and cyclisation ratio of branched tetraethers (CBT) proxies were used to calculate the mean annual air temperature (MAAT) and pH values of the organic-rich horizons at time of deposition. The Branched versus isoprenoid index of tetraethers (BIT) was used to assess the relative contributions of marine archaeal and terrestrial bacterial tetraethers, and thereby assess the validity of the MBT, CBT and calculated palaeoenvironmental factors. The results presented in this thesis suggest that the use of the MBT/CBT proxy has significant potential in southern Africa, and may complement previously attempted palaeoclimatic and palaeoecological studies of Neogene-aged South African sediments. This type of research has the capacity to provide palaeoenvironmental information where other proxies may be absent. Results indicate that all sites yielded branched tetraether membrane lipids with the exception of Rondeberg, where GDGTs were below detection as a result of poor preservation conditions. Palynological investigation confirmed proxy derived temperatures. Furthermore palynomorph analyses supplemented earlier studies of the Noordhoek site and were piloted for the Rondeberg site, reaffirming alternating sequences of tropical and subtropical palynofloras. The MAATs, likewise, show variability and pronounced trends through time at the Langebaanweg and Noordhoek sites, generally corresponding with the variation and diversity of the pollen population. The terrestrial MAAT results appear to compliment Southern Hemisphere sea level changes associated with Antarctic glaciations. Additionally, this data shows a pattern similar to the Southern and Northern Hemisphere marine isotope records of relative fluctuations in the global climate and sea level change from the early to middle Miocene. The application of these past climate change indicators have been proved to be useful in the reconstruction of South Africa Miocene palaeoclimates, and may aid in understanding the consequences of climate change in the Cape region

Position of the Triassic-Jurassic boundary in South Africa and Lesotho : a multidisciplinary approach aimed at improving the chronostratigraphy and biostratigraphy of the Elliot Formation, Stormberg Group

The continental red bed succession of the main Karoo Basin in South Africa and Lesotho, the Elliot Formation (Stormberg Group, Karoo Supergroup), is a significant stratigraphic unit for the regional and global understanding of the Late Triassic - Early Jurassic evolution of terrestrial vertebrate faunas, however, the temporal resolution of its biostratigraphy is inadequate for detailed regional and global correlations. The main aim of this dissertation is to build a more comprehensive chronostratigraphic framework of the Late Triassic - Early Jurassic Elliot Formation by combining and constraining its biostratigraphy with new results obtained using magnetostratigraphic techniques. This dissertation presents magnetostratigraphic data from ten measured stratigraphic sections in the Elliot Formation across the main Karoo Basin in South Africa and Lesotho

The sauropodomorph biostratigraphy of the ElliotFormation of southern Africa: Tracking the evolution ofSauropodomorpha across the Triassic–Jurassic boundary

The latest Triassic is notable for coinciding with the dramatic decline of many previously dominant groups, followed by the rapid radiation of Dinosauria in the Early Jurassic. Among the most common terrestrial vertebrates from this time, sauropodomorph dinosaurs provide an important insight into the changing dynamics of the biota across the Triassic–Jurassic boundary. The Elliot Formation of South Africa and Lesotho preserves the richest assemblage of sauropodomorphs known from this age, and is a key index assemblage for biostratigraphic correlations with other similarly-aged global terrestrial deposits. Past assessments of Elliot Formation biostratigraphy were hampered by an overly simplistic biozonation scheme which divided it into a lower “Euskelosaurus” Range Zone and an upper Massospondylus Range Zone. Here we revise the zonation of the Elliot Formation by: (i) synthesizing the last three decades’ worth of fossil discoveries, taxonomic revision, and lithostratigraphic investigation; and (ii) systematically reappraising the stratigraphic provenance of important fossil locations. We then use our revised stratigraphic information in conjunction with phylogenetic character data to assess morphological disparity between Late Triassic and Early Jurassic sauropodomorph taxa. Our results demonstrate that the Early Jurassic upper Elliot Formation is considerably more taxonomically and morphologically diverse than previously thought. In contrast, the sauropodomorph fauna of the Late Triassic lower Elliot Formation remains relatively poorly understood due to the pervasive incompleteness of many key specimens, as well as the relative homogeneity of their diagnostic character suites. Our metrics indicate that both Elliot Formation and global sauropodomorph assemblages had greater morphological disparity within the Early Jurassic than the Late Triassic. This result is discussed in the context of changing palaeoclimatic conditions, as well as macroevolutionary events associated with the end-Triassic extinction

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

.

The Late Sinemurian ichnofossils from Mampoboleng (Upper Moyeni), Lesotho

.

Subeng vertebrate tracks: digital archive of a historic Upper Triassic palaeosurface (lower Elliot Formation), Leribe, Lesotho

Here we present the results of our sedimentological, stratigraphic and ichnological investigations at a historic ichnosite in NE Lesotho that is among the first documented vertebrate track-bearing palaeosurfaces in southern Gondwana. <br><br>Contains the Subeng Agisoft 3D model (and associated photographs) in addition to the CloudCompare model and rendered palaeosurface figure

Sedimentology and ichnology of the Mafube dinosaur track site (Lower Jurassic, eastern Free State, South Africa): a report on footprint preservation and palaeoenvironment

Footprint morphology (e.g., outline shape, depth of impression) is one of the key diagnostic features used in the interpretation of ancient vertebrate tracks. Over 80 tridactyl tracks, confined to the same bedding surface in the Lower Jurassic Elliot Formation at Mafube (eastern Free State, South Africa), show large shape variability over the length of the study site. These morphological differences are considered here to be mainly due to variations in the substrate rheology as opposed to differences in the trackmaker’s foot anatomy, foot kinematics or recent weathering of the bedding surface. The sedimentary structures (e.g., desiccation cracks, ripple marks) preserved in association with and within some of the Mafube tracks suggest that the imprints were produced essentially contemporaneous and are true dinosaur tracks rather than undertracks or erosional remnants. They are therefore valuable not only for the interpretation of the ancient environment (i.e., seasonally dry river channels) but also for taxonomic assessments as some of them closely resemble the original anatomy of the trackmaker’s foot. The tracks are grouped, based on size, into two morphotypes that can be identified as Eubrontes -like and Grallator -like ichnogenera. The Mafube morphotypes are tentatively attributable to large and small tridactyl theropod trackmakers, possibly to Dracovenator and Coelophysis based on the following criteria: (a) lack of manus impressions indicative of obligate bipeds; (b) long, slender-digits that are asymmetrical and taper; (c) often end in a claw impression or point; and (d) the tracks that are longer than broad. To enable high-resolution preservation, curation and subsequent remote studying of the morphological variations of and the secondary features in the tracks, low viscosity silicone rubber was used to generate casts of the Mafube tracks

Magnetostratigraphy across the Triassic-Jurassic boundary in the main Karoo Basin

The end-Triassic mass extinction and the transition and explosive diversification of fauna over the Triassic-Jurassic boundary is poorly understood and poorly represented in the rock record of the Southern Hemisphere. This is despite the rich diversity in both body and trace fossils of Triassic-Jurassic age in southern Africa, which is not found in coeval Northern Hemisphere localities. We report here the first palaeomagnetic polarity zonation of the Upper Triassic-Lower Jurassic continental red bed succession (Elliot Formation; Stormberg Group) in southern Africa. The results from 10 partially overlapping sections, with a composite thickness of ~ 280 m, provide a magnetic polarity chronology of the main Karoo Basin in South Africa and Lesotho. Palaeomagnetic analyses reveal that heating samples to between 150 °C and ~ 300 °C removes the secondary, moderately inclined (~ 48°) normal-polarity component of remanent magnetization. This component overlaps with the present-day field and is comparable to the overprint direction expected from Lower Jurassic Karoo dolerite intrusions. In contrast, a likely primary, high unblocking temperature component, of dual polarity, consistently is of steeper inclination (~ 63°). This characteristic remanence passes the reversals test, except where means are based on small sample populations. There are only two resulting polarity zones for the ~ 200 m thick lower Elliot Formation (LEF) with potential for a thin 3rd magnetozone in the uppermost part. The upper Elliot Formation (UEF), in contrast, which was sampled over a thickness of ~ 80 m, has five polarity zones. The failure of the reversal test for the UEF and combined Elliot Formation (LEF + UEF) indicates that the normal polarity samples may be biased by a younger overprint of either the Jurassic normal polarity of the Karoo Large Igneous Province or present day field. The separate poles calculated for the four sites in the LEF and ten sites in the UEF overlap with the Late Triassic and Early to Middle Jurassic Gondwana poles, respectively. The combined Elliot Formation and UEF pole positions are better constrained than the LEF and therefore considered more reliable. Overall the LEF shows considerable overlap with the Late Triassic Apparent Polar Wander Paths (APWP) poles.Research funds received from African Origins Programme of the National Research Foundation (Grant no. 77782 and 82606) of South Africa (by EB as principal investigator; MdK, FK as co-investigators) are gratefully acknowledged. LS would also like to acknowledge the support of the NRF/DAAD doctoral scholarship, and DST-NRF Centre of Excellence in Palaeosciences (CoE in Palaeosciences) postdoctoral fellowship and the UCT Postgraduate Publication Incentive (PPI) award.Peer reviewe

Basal sauropodomorph locomotion: ichnological lessons from the Late Triassic trackways of bipeds and quadrupeds (Elliot Formation, main Karoo Basin)

Using modern ichnological and stratigraphic tools, we reinvestigate two iconic sauropodomorph-attributed tetradactyl ichnogenera, Pseudotetrasauropus and Tetrasauropus, and their stratigraphic occurrences in the middle Upper Triassic of Lesotho. These tracks have been reaffirmed and are stratigraphically well-constrained to the lower Elliot Formation (Stormberg Group, Karoo Basin) with a maximum depositional age range of <219–209 Ma (Norian). This represents the earliest record of basal sauropodomorph trackways in Gondwana, if not globally. Track and trackway morphology, the sedimentary context of the tracks, and unique features (e.g., drag traces) have enabled us to discuss the likely limb postures and gaits of the trackmakers. Pseudotetrasauropus has bipedal (P. bipedoida) and quadrupedal (P. jaquesi) trackway states, with the oldest quadrupedal Pseudotetrasauropus track and trackway parameters suggestive of a columnar, graviportal limb posture in the trackmaker. Moreover, an irregularity in the intermanus distance and manus orientation and morphology, in combination with drag traces, is indicative of a non-uniform locomotory suite or facultative quadrupedality. Contrastingly, Tetrasauropus, the youngest trackway, has distinctive medially deflected, robust pedal and manual claw traces and a wide and uniform intermanus distance relative to the interpedal. These traits suggest a quadrupedal trackmaker with clawed and fleshy feet and forelimbs held in a wide, flexed posture. Altogether, these trackways pinpoint the start of the southern African ichnological record of basal sauropodomorphs with bipedal and quadrupedal locomotory habits to, at least, c. 215 Ma in the middle Late Triassic