The Mesoarchaean West Rand Group displays a layer-cake stratigraphy with lithostratigraphic units correlatable on a basin-wide scale. The ~5 km thick succession consists of fluvial braidplain and shelf deposits, which range from shallow inner shelf marine orthoquartzites, outer shelf argillites to starved shelf iron-formations. Three major sequences are present: Sequence I (Hospital Hill Subgroup), Sequence II (Government Subgroup) and Sequence III (Jeppestown Subgroup).

Sequence I was deposited during a period of highstand of sea-level, sequence II during a period of relative lowstand, and sequence III during a period of relative highstand coupled with high rates of sediment supply. Isopach, depofacies and palaeocurrent analyses indicate that strata in the western to northwestern parts of the basin were deposited under more proximal sedimentary conditions compared to those in the central or southeastern parts. Little relationship between the present outline of the basin and the distribution of depofacies suggests that the original sedimentary basin was significantly larger in areal extent.

Depofacies and thickness distribution, as well as synsedimentary deformation of strata, indicate that the basin was most probably of flexural tectonic origin. These findings support deposition in a wide, shallow, and rather stationary foreland basin, with an axial zone towards the west/northwest and low amplitude peripheral bulge to the east/southeast. Such shallow foreland basins, with abundant sediment bypassing, are thought to be associated with windward-facing orogenic fronts. High rates of erosion along such fold-thrust belts lead to ineffective loading and advancement of the orogenic front, as well as an oversupply of sediment.

The Bromacker Project (https://bromacker.de/) investigates the “Ursaurier” vertebrate Lagerstätte of the same name in Early Permian redbeds of the Tambach Formation. Its geologic-paleontologic subproject contributes key parameters such as paleoecology, paleoclimate, paleogeography, and depositional environments to the reconstruction of the Tambach Basin.

Two research boreholes were drilled in 2022 and 2023 to complement information from outcrops and several legacy boreholes near the Bromacker site. Forschungsbohrung (Fb) Altenbergen 01/2022, located in the northwest of the basin, cored 250 m of the Tambach Formation and terminated in the basal Bielstein Conglomerate Member. Fb Tambach-Dietharz 01/2023 in the southeast of the basin terminated at 199 m depth in the pre-Tambach Rotterode Fm. The Bielstein Conglomerate Member is correlated between both boreholes; it consists of well-rounded volcanic clasts of a braided river setting. In the Altenbergen borehole, fluvial deposits of the Tambach Sandstone Member consist of massive mudstones interbedded with laminated shale in fluvial floodplain settings interspersed with temporary ponds and paleosols; whereas this member is present as gravelly fluvial-channel sandstone facies in the Tambach-Dietharz borehole. Fluvial channel deposition is terminated by prograding alluvial fan sedimentation represented by the Finsterbergen Conglomerate Member present in both cores. The influx of fluvial sandstones bearing plutonic and metamorphic clasts, observed in both boreholes, marks the exposure of the Ruhla Crystalline Complex to the west.

Especially the Tambach Sandstone Member shows different sedimentary facies throughout the core on a distance within the basin of around 4 km, showing also a clear distinction between habitats within the Tambach Basin.

A common tool in provenance studies of clastic sedimentary rocks is the geochemical composition for identification and differentiation of potential catchment areas. However, not only source rock lithologies but also for instance sorting, alteration, leaching or new mineral formation influenced by the climate during erosion, transport and deposition or by diagenesis during burial influence the geochemical provenance signal (Augustsson et al., 2023). Therefore, the consideration of the genetic and diagenetic changes of the deposits, i.e. their development over time, plays an important role for a meaningful interpretation of geochemical data for provenance studies.

To test this, we investigate Permo-Carboniferous terrestrial sandstone and conglomerate. The units represent changing palaeogeographic and climatic conditions. In addition, the deposits underwent diagenetic changes during deep burial and partial uplift to present-day borehole depths of 1500-2500 m. We use polarization, cathodoluminescence, and scanning electron microscopy, microprobe analyses, XRD, XRF, and ICP analyzes. Initial results indicate correlations of the Chemical Index of Alteration and K₂O/Na₂O with the preservation state of detrital feldspar and the diagenetic clay minerals kaolinite and illite. Th/Sc and Y/Zr correlate with lithoclast composition (felsic versus mafic igneous and metamorphic) and the intergranular components (matrix versus cement). This allows the separation of Carboniferous and Permian samples. It is a result of changing climatic and diagenetic conditions.

Reference: Augustsson, C., Aehnelt, M., Olivarius, M., Voigt, T., Gaupp, R., & Hilse, U. (2023). Provenance from the geochemical composition of terrestrial clastic deposits-a review with case study from the intracontinental Permo-Triassic of European Pangea. Sedimentary Geology, 106496.

The Triassic Skagerrak Formation in the Central Graben of the North Sea is a fluvial-lacustrine succession that is historically difficult to subdivide in the subsurface into lithostratigraphic units, and to correlate between different wells and licence blocks. The formation consists of various sandstone members interspersed by mudstone members with relatively poor age constraints. Raman spectroscopy of heavy minerals in combination with chemostratigraphy is an effective tool to identify lithological differences and to reconstruct provenance of the individual members. The lower parts of the Skagerrak Formation (Judy Sandstone Member) are generally characterised by ultra-stable heavy mineral assemblages, indicating multi-recycling of nearby Palaeozoic cover units, while the directly underlying Bunter Sandstone additionally has several unstable mafic heavy mineral species, probably derived from local basement highs (e.g., Forties Montrose High). Up-section within the lower parts of the Joanne Sandstone Member there is a switch to more immature apatite-rich heavy mineral assemblages, likely related to a source change to Fennoscandian basement at the Norwegian margin. A mafic marker horizon within the upper Joanne Sandstone indicates input from contemporaneous volcanism at the Carnian-Norian boundary, and may represent a significant basin-wide unconformity.

The present-day hyperarid Sahara is the largest hot desert in the world, but its development in deep time is largely unknown. The inception of persistent Northern African aridification has been variously linked to the onset of Northern Hemisphere glaciation at the beginning of the Pleistocene. However, eolian bedforms and dust records, reinforced by modelling studies, indicate transient periods of aridity have started North Africa already in the latest Miocene during times of Northern Hemisphere cooling. For the globally warm Pliocene epoch intermittent aridity is suggested for the western Sahara by dust records from the Canary Islands. In contrast, onshore evidence of contemporary North African climate is missing, because of the lack of well-dated Neogene sections in the Sahara.

Here we present a thoroughly sedimentological, paleoenvironmental and geochronological investigation of the Neogene continental Wadi El Natrun Formation in the northern fringe of eastern Sahara (Wadi El Natrun, northern Egypt). We differentiate seven sedimentological facies types, each distinguished by characteristic palaeobiota. These are in an ascending order: braided river and overbank facies, which contain abundant fluvial and riparian vertebrates; a lacustrine black shale facies rich in phytoclasts; a lacustrine limestone facies with characean algae; a marine limestone facies with planktonic foraminifera and marine molluscs; a playa lake facies with a thalassosaline ostracod and gastropod fauna; an ephemeral stream facies with Skolithos and Ophiomorpha ichnofabrics; and finally an eolian dune facies with polydomic ichnofabrics.

These changes in sedimentological facies indicate the long-term temporal progression of desertification in Northern Africa well before the Quaternary.

Deep-time reconstruction of palaeoenvironments is of great importance for many geoscientific and life science disciplines. Various geoarchives provide information on ancient dust fluxes that affect climate and biodiversity and which also hold clues to palaeogeography. Furthermore, "rates" are integral to almost all related research questions, requiring the use of state-of-the-art dating techniques on various materials that act as dust traps.

Intercontinental dust fluxes, such as those from the African deserts to South America cause large-scale geo-bio interactions. Such wind-blown particles fertilise the vibrant ecosystems of the Amazon rainforrest, where the dust is rapidly metabolised or bioturbated by countless organisms. Saharan dust transported to Europe is also difficult to trace back through time, as single events rarely result in detectable deposits. This calls for alternatives to conventional drilling or outcrop studies. Datable dust archives containing detrital heavy minerals provide snapshots of dust transport in a high spatio-temporal resolution. Therefore, analyses like LA-ICP-MS U-Pb age determination on detrital zircon or SEM-EDX chemical characterisation on large numbers of individual terrestrial dust particles are applied.

However, even the most advanced techniques for exploiting new geoarchives are of limited benefit without information on the original dust sources and their availability over time. For this reason, the evolution of drainage systems through time is studied in particular, as rivers are often the primary source of desert sediments. This whole approach involves compilation and processing of large datasets, e.g. a circum-Atlantic zircon age database (N>5000, n>275000). Initial results are very encouraging and go beyond the proof-of-concept stage.