4:15pm - 4:45pmSession Keynote
Joining up the Dots: Regional Geology Insights from the Arabian Plate and the Black Sea
Halliburton, United Kingdom
One of the many attractions of geoscience is the necessity to make predictions. That it is to say, to take observations made at a certain locality and extrapolate the inferences into areas where there is little or no data. For example, consider the Black Sea, a basin with limited data over an area that covers 423,000 km2, and that contains a sedimentary thickness of up to 14 km. Data from the margins of the basin, for example from the Pontides or the Caucasus, can be used to determine the timing and nature of the sedimentary fill, but to do so, the context of regional geology is needed. Similarly, much of the geology of the Arabian Plate is known from outcrops mostly on the margins of the plate, and subsurface penetrations. Once again, a methodology is required to join this data together and predict between datapoints.
Two aspects of regional geology are key. Firstly, an understanding of the tectonic evolution of the region in question. This can be obtained from an integration of a geodynamic plate model with observations from the rock record. Deep seismic records also help elucidate tectonic history. Secondly, the application of a biostratigraphically-constrained sequence stratigraphic model that provides a high-resolution framework for correlation and implies a predictable stratigraphic architecture. Using such tools, geoscientists can utilise and integrate all the data at their disposal to make predictions into the unknown. These can be expressed as palaeogeographic maps with consequent application in the search for resources and carbon repositories.
4:45pm - 5:00pm
The Pleistocene sediments of the Palaeoatbara in eastern Sudan as an archive for the evolution of the Nile river system
1Institute of Applied Geosciences, Technische Universität Berlin, Ernst-Reuter-Platz 1, 10587 Berlin, Germany; 2Museum für Naturkunde, Invalidenstrasse 43, 10115 Berlin, Germany; 3PACEA, CNRS/Université de Bordeaux, Allée Geoffroy Saint-Hilaire 33615 Pessac CEDEX, France; 4Leibniz Institute for Applied Geophysics, Stilleweg 2, 30655 Hannover, Germany; 5Faculty of Minerals and Oil, International University of Africa, 11121 Khartoum, Sudan; 6Department of Anatomy, Western University of Health Sciences, Pomona, CA 91711, USA; 7Faculty of Petroleum and Minerals, Al Neelain University, 11121 Khartoum, Sudan
Geological evidence and geodynamic modelling suggest that the Nile river system has been largely stable since its origins ~30 Ma. The Nile could have provided a long-term migration route for vertebrates including hominins between Eastern and Northern Africa. However, other geological data contradict such an old stabilisation of the course of the Nile. Fieldwork along the middle stretches of the Atbara River, the last tributary to the Nile before it crosses the Sahara, provides evidence for a complex fluvial history during the last 450 ka, with several periods of fluvial re-establishment that differ markedly in their fluvial style and hydrodynamics. While some rivers were dominated by gravelly and sandy braid bars, others had prominent fine-grained point bars, and some were perennial, while others showed high discharge variance, with significantly varying catchment areas. The fine-grained floodplain deposits contain different types of paleosols, but predominantly evidence seasonal and semi-arid conditions. The changes in river style, discharge dynamics and catchments can be attributed to Pleistocene climatic changes and to tectonic processes. The riverine landscapes of the Palaeoatbara were colonised by a diverse fauna including hominins which are represented by fossils and stone tool remains. The study of the sediments, fossils and archaeology along the middle Atbara, together with high-resolution age dating, provide new insights into the history of the Nile river system, and has implications for our understanding of early hominin migrations and the formation of modern ecosystems in Africa.
5:00pm - 5:15pm
Large regional structures from puzzle pieces - the hidden Triassic rift on the western flank of the Eichsfeld-Altmark-Swell
1Landesamt für Geologie und Bergwesen Sachsen-Anhalt, Germany; 2Georg-August-Universität Göttingen, Germany; 3Deutsche Geologische Gesellschaft – Geologische Vereinigung e.V.
The incorporation of regional geologic knowledge is essential to solve multiple geological questions in any defined research area meaning that small-scale observations must fit with general regional interpretations as well as the tectonic and sedimentary setting. Conversely, in areas with sparse subsurface information, a conceptional knowledge of the observed area must be developed by incorporating and combining small-scale indications into a sound regional geologic model.
In this contribution, we collect some of these small-scale “puzzle pieces” observable along the western flank of the Eichsfeld-Altmark-Swell in Central Germany. This structure is assumed to form a roughly NNE-SSW-trending Permo-Triassic sedimentary high, which is constrained by reduced thickness, facies changes and unconformities in Late Permian to Late Triassic strata. In parts it is accompanied by areas where Zechstein is directly overlain by shaly to evaporitic Upper Buntsandstein/Middle Muschelkalk while several hundred meters of sandy Lower and Middle Buntsandstein are missing. We combine local observations published in cross-sections, outcrop situations, few boreholes and reflection seismics, which occur along a some 200 kilometres long strip in central Germany and attempt to put them in a regional geologic context. Our results for the spatial relationship of sedimentary basins and bordering normal faults as well as associated salt structures indicate that the western flank of the Altmark Swell was affected by huge sub-horizontal, decoupled movements (up to 5 km extension) along ramp-flat normal faults involving two evaporite detachments. Although sparse, some indications are available for gently dipping basement faults that accommodated these movements below the Zechstein salt.
5:15pm - 5:30pm
Aeolianites of the Detfurth Formation (Middle Buntsandstein, Lower Triassic) in the Hessian Depression: spatial distribution and stratigraphic affiliation with regard to modern stratigraphic concepts and use in applied geosciences
Hessian Agency for Nature Conservation, Environment and Geology (State Geological Survey), Germany
This talk focusses on the Detfurth Formation of the Hessian Depression and aims to point out a modern way of subdividing the sedimentary record, serving as a profound basis in applied geoscientific disciplines such as geothermal exploration, hydrogeology, or 3D modelling. Particular attention is paid to aeolian sediments, as they have different rock properties compared to fluvial sediments.
Aeolian sediments are widespread along the western margin of the Hessian Depression, locally building up the entire Detfurth Formation. Towards the central Hessian Depression, they interfinger with aquatically deposited sediments of the Detfurth Formation, yet are widely traceable in its lower part. Interestingly, similar aeolianites regionally also occur above the Detfurth Claystone unit, and then usually were assigned to the Hardegsen Formation, following the fining-upward principle of the Buntsandstein “Folgen” – with some doubts remaining (Dersch-Hansmann et al. 2013, SDGG).
Based on detailed sedimentological recordings of core drillings, a facies model of aeolian and alluvial sand plains, braided rivers, deltas, and the central playa lake system is proposed (Hug-Diegel 2021, ZDGG). The correlation scheme also illustrates that spatial relationships of the Detfurth subformations in the Hessian Depression clearly deviate from a “layer-cake geometry”. For geogenetic reasons and due to their special rock properties, the aeolianites should be combined in a separate subformation, but assigned to the Detfurth Formation. This is consistent with the idea of a dual subdivision of the Buntsandstein into both regional geochronologic units (allostratigraphic “Folgen”; Lutz et al. 2005, Newsl. Strat.) and – independent – lithofacies-stratigraphic units (formations).
5:30pm - 5:45pm
Climate, volcanoes, and tectonic activity - Their influence on the lower to middle Eocene paleoenvironment on the Sprendlinger Horst (Southwest Germany)
1TU Darmstadt, Germany; 2Senckenberg Forschungsinstitut und Naturmuseum, Germany
The Sprendlinger Horst represents the northern extension of the Odenwald basement which is flanking the Upper Rhine Graben to the northeast. Several small, isolated basins filled by lacustrine sediments of Eocene age are known from the area. Most of them represent the filling of maar-type volcanic structures, such as the lakes at Messel, Offenthal and Groß Zimmern. Only Lake Prinz von Hessen near Darmstadt represents a small pull-apart basin. High resolution palynological analyses of drill cores from these four nearly coeval lake basins allows to reconstruct the vegetation during the last natural greenhouse system in Central Europe.
Quantitative palynological data from the deposits of the four lakes prove that the vegetation generally shows the same succession with a recolonization phase at the beginning, followed by a recovery and a terminal climax phase. The record may be incomplete for some of the lakes, but an extensive data set including nearly 1000 samples shows that each basin has its unique story to tell. For example, in Messel the undisturbed record of about 600.000 years reveals the influence of orbital forcing on the climate and the composition as well as on the diversity of the climax vegetation during the early middle Eocene. In contrast, at lakes Prinz von Hessen and Groß Zimmern regional tectonic and seismic activity had a more pronounced influence on the paleoenvironment than orbitally controlled climate change.