Conference Agenda

The early Permian Tambach Formation has been extensively studied as the host of the Bromacker vertebrate lagerstätte within central Pangea. Two research boreholes and extensive multidisciplinary field work accompanied a five-year paleontological open-science excavation at this site.

Deposition of the Tambach Formation follows an episode of erosion within the Thuringian Forest Rotliegend succession which resulted in a low-angle unconformity. Sedimentation was initially largely controlled by paleorelief inherited from volcanism in the east and began through change in an (as yet unknown) base level. The basal Bielstein-Konglomerat (clasts composed exclusively of Rotliegend rhyolites) was deposited by perennial braided streams, sourced in a volcanic plateau east of the basin. It forms a continuous fining-upward cycle with the overlying Tambach-Sandstein, formed in sandy fluvial channels sided by an episodically inundated floodplain. Granitic pebbles in the Bromacker-Sandstein mark the onset of a new coarsening-upward cycle. Shale-lined reactivation surfaces with mudcracks within fluvial channels indicate periodic desiccation of the fluvial system. The trend towards more episodic fluvial transport continues in the Finsterbergen-Konglomerat, deposited by ephemeral distributary fluvial systems. The overall trend towards a more seasonal climate is accompanied by influx of granitic and metamorphic clasts within the Bromacker-Sandstein and Finsterbergen-Konglomerat from the Northwest, linked to tectonic relief building within parts of the Mid German Crystalline High.

A thin tuff layer right above the vertebrate lagerstätte in the Bromacker-Sandstein dates these climatic and tectonic events to the late Asselian (294.1 ± 0.4 Ma). Cyclostratigraphic analysis of both cores suggests that they occurred within approx. 2.1 Myr.

The Eichsfeld-Altmark swell (EAS) is a regional, elongated, NNE-trending basement arch originally defined by reduced Zechstein and Buntsandstein thicknesses. Its western flank coincides with an en-échelon array of (mostly normal) faults and salt structures. Many of these structures show a similar combination of stratigraphic and structural features: Km-wide (in E-W-direction) areas of reduced or absent lower to middle Buntsandstein are underlain by strongly thinned Zechstein salt and overlain by Keuper depocenters. These are commonly flanked to the east by salt diapirs or normal faults associated with salt rollers in their footwalls. The underlying, gently west-dipping basement is unfaulted or at best offset by much smaller faults than those affecting the sedimentary cover. Two scenarios might explain the associated thinned Buntsandstein and thickened Keuper: (1) Stepped normal faults of Keuper age with bedding-parallel segments soling into a basal Zechstein detachment transporting detached Upper Buntsandstein and Muschelkalk on Zechstein and creating hanging-wall half grabens with thick Keuper infills or (2) wide salt pillows rising passively during Buntsandstein deposition, arrested during late Buntsandstein and Muschelkalk times and reactivated in Keuper time to evolve into diapirs with deep peripheral sinks. Scenario (1) cannot explain structures that have only small gaps in the Muschelkalk whereas scenario (2) raises the question of why salt rise ceased temporarily before resuming later. Both scenarios suggest substantial, E-W to NE-SW-directed, thin-skinned extension. Where the basal detachment roots into basement faults is yet another, unanswered question.

Schleswig-Holstein lies within the North German Basin, which is characterised by complex salt tectonics. The mobilisation of thick Permian Rotliegend and/or Zechstein evaporite sequences has resulted in the formation of numerous salt domes and diapirs. While these structures are primary targets for energy storage and hydrocarbon traps, they also act as 'geological windows', enabling us to study the deep subsurface.

During the halokinetic process, salt migrates upwards, cutting through and displacing kilometres of overlying Mesozoic and Cenozoic strata. This vertical transport brings deeply buried lithologies nearer to the surface or within reach of standard drilling depths, which would otherwise remain inaccessible beneath several kilometres of overburden.

This study investigated the Elmshorn and Quickborn salt dome structures, which are both known for their geohazardous activity, such as sinkhole formation. A total of 583 metres of cuttings and drill core were collected from six shallow holes (end-of-hole depths <110 metre) with Permian cap rocks already being intersected between 20 and 50 metres. The cuttings and drill core were described petrographically, and selected samples were analysed using geochemical, mineralogical, and isotopic methods to reveal the formation and alteration history of the two salt domes.

Preliminary results suggest that both salt domes have complex formation histories, with significant variations occurring within a single dome over a distance of just a few hundred metres. However, some Zechstein strata are identical at both sites. There is also evidence of the influence of meteoric water, which causes karst formation and hydrates primary sulphates, at both sites.

Within the quaternary Eifel Volcanic Field there are some rare occurrences of Tertiary volcanic rocks, with unknown affinities to the nearby Hocheifel (HEVF) and Siebengebirge-Volcanic-fields (SVF) [1, 2]. These lavas were associated with the extension of the Upper Rhein Graben since the Eocene [3]. The Tertiary volcanic rocks occur in the Brohltal region of the East-Eifel and were previously suggested to represent the southernmost extent of the late Oligocene and early Miocene SVF. However, currently, geochemical data for lavas from the Kahlenberg supporting this idea are inconclusive [2].

We present updated bulk rock major element (XRF), trace element (TQ-ICP-MS), and new radiogenic Hf, Sr, and Nd) isotope data (MC-ICP-MS to characterise the alkali basalts from Kahlenberg and two further basanites of the Brohltal region previously related to the HEVF. Major element compositions confirm basaltic and basanitic lithologies with a low degree of differentiation, consistent with the other Tertiary volcanic fields (HEVF, SVF) of the Rhenish Massif [2]. Hafnium-Nd isotope ratios of the Kahlenberg lava flow, are slightly more radiogenic than those expected of the SVF but Nd compositions overlap compositions of the HEVF. The Multi-element patterns don't correlate perfectly with those expected of both volcanic fields. These results question previous notions of a genetic relationship between the Kahlenberg and the SVF, better constraining the spatial extent of the respective volcanic fields [2]. These preliminary results will be supplemented with pending and Sr isotope data.

1 Schmincke, (2007)

2 Kolb et al., (2012)

3 Fekiacova et al., (2007)

Eruptive recurrence and spatiotemporal clustering in continental intraplate fields are critical for assessing controls on mantle melting, magma ascent, and venting. Here, we apply zircon U-Th-Pb and (U-Th)/He dating of crustal xenoliths entrained during magma ascent, preserved in proximal maar and scoria cone deposits in the West and East Eifel volcanic fields (WEVF and EEVF). In combination, these data reveal deep crustal structures and, importantly, refine eruption ages that are otherwise difficult to obtain in deposits from explosive volcanism in continental settings.

Zircon U-Th-Pb crystallization ages distinguish metaigneous and metasedimentary xenoliths from the Palaeozoic basement of the Rhenish Massif, and reveal previously unrecognized magmatism during the Permian, Paleogene and Middle Pleistocene. Zircon (U-Th)/He eruption dating for WEVF volcanoes identified two volumetrically dominant clusters at c. 25 ka (Daun maars, Pulvermaar, Wartgesberg, Facher Höhe) and 75 ka (Meerfelder Maar, Mosenberg), coinciding with deposition of the Eltville and Rocourt tephras, respectively. The eruption of Oberwinkler Maar (195±7 ka) falls into a previously inferred volcanic hiatus for the WEVF, coinciding with a major eruptive episode in the EEVF, with several basanitic scoria cones (Fornicher Kopf, Eppelsberg, Tönchesberg, Rothenberg, Hummerich, Karmelenberg) yielding analytically indistinguishable (U-Th)/He eruption ages of c. 200 ka.

Zircon (U–Th)/He dating of pyrometamorphic crustal xenoliths thus provides a robust chronological framework that identified field-wide eruptive pulses in close temporal succession in the WEVF and EEVF. New evidence for eruptive pulsing calls for a re-evaluation of previously postulated climatically modulated eruptive activity in non-glaciated intraplate volcanic fields such as the Eifel.

Geothermal energy is an important climate and environmentally friendly energy source. Detailed and comprehensive information of the geology and structures of the subsurface are essential for geothermal projects. Therefore, the Geological Survey of North Rhine-Westphalia (GD NRW) publishes geological model data, digitalized legacy data and newly acquired data in the geothermal online-portal of NRW.

For the past 20 years, the online portal “Geothermie in NRW” has been successfully used for shallow geothermal projects. In early 2023, it was expanded to include intermediate and deep geothermal systems through a comprehensive data update, initially covering the Rhineland and northern margin of the Rhenish Massif. The following update in 2025 included the Ruhr region and Central Münsterland. In the most recent update, subsurface models were updated and expanded to include the Münsterland, Ostwestfalen-Lippe, the entire Rhenish Massif and the Northern Rhineland. The remaining parts of NRW will be included progressively in future updates.

Four potential geothermal reservoir horizons were modelled in NRW: Upper Cretaceous limestones, the Lower Carboniferous “Kohlenkalk”, the Upper and Middle Devonian “Massenkalk” and the Lower Triassic Buntsandstein. Recently, a layer for ATES (Aquifer Thermal Energy Storage) was added, based on sandstones of the Tertiary Grafenberg Formation and further Tertiary formations. All models integrate both legacy and new data from 2D seismic surveys and drillings, as well as geological sections. Initiated by the ministry of economic affairs, industry, climate action and energy of NRW, the project “Explorations- und Bohrprogramm NRW” will continue to acquire and integrate new data until 2028.