Large megathrust earthquakes like the 2011 Mw 9.0 Tohoku earthquake (Japan) are followed by numerous aftershocks in the subduction zone forearc overlying the seismogenic fault. The aftershocks in the forearc can include normal-faulting events despite the thrust mechanism of the main shock. Postseismic normal faulting has been explained by stress changes induced by the coseismic stress drop along the megathrust. However, details of stress changes in the forearc and aftershock triggering mechanisms remain poorly constrained. Here we use numerical force-balance models combined with Coulomb failure analysis to show that the megathrust stress drop indeed supports normal faulting, but that forearc-wide triggering of aftershocks is feasible within a narrow range of megathrust stress-drop values and forearc stress states only [for details see Dielforder et al., 2023]. We determine this range for the Tohoku earthquake and show that the associated stress changes explain the aftershock seismicity in unprecedented detail. In particular, our analysis reveals that ~78% of the aftershocks and ~92% of the seismic moment release occurred in areas where the Tohoku earthquake caused a stress increase, and that the detailed aftershock distribution was also governed by spatial variability in fault strength and forearc topography. Our findings provide new insights into aftershock triggering and help to understand where aftershocks occur after great earthquakes at subduction zones.

Dielforder, A., Bocchini, G. M., Kemna, K., Hampel, A., Harrington, R. M., & Oncken, O. (2023). Megathrust stress drop as trigger of aftershock seismicity: Insights from the 2011 Tohoku earthquake, Japan. Geophysical Research Letters, 50, e2022GL101320. https://doi.org/10.1029/2022GL101320

Slow-slip events (SSEs), although widely recorded in various convergent margins globally, only recently have been reported in the Eastern Mediterranean, with one of them triggering the 2018 ~M7 Zakynthos Earthquake along the western Hellenic Subduction System (HSS). Here, we explore the distribution, size and duration of SSEs along the HSS and assess their importance in subduction-related strain accumulation and release. To achieve this, we analyse geodetic timeseries from a dense network of permanent GNSS stations on Western Peloponnese, Crete and surrounding islands that collectively span a time-period of ~10 years. We use greedy linear regression techniques to estimate displacement trajectory models for each station and thus we identify transient displacement signals, associated with aseismic processes at depth. To further constrain the spatial extent and size of the SSEs we invert the GNSS transient displacements for variable distributed slip at depth and we, therefore, discuss likely scenarios of aseismic and seismic strain distribution (and partitioning) within the HSS’s complex plate-interface zone.

Central New Zealand (southern North Island/northern South Island) occupies a complex transition from subduction to strike-slip at the southern termination of the Hikurangi subduction zone. This transition was also the site of the 2016 M7.8 Kaikoura earthquake, which is the most complex earthquake ever recorded, involving rupture of over a dozen faults. I will discuss how this transition from subduction to strike-slip occurs, through a joint interpretation of geologic and geodetic data. Approximately 2 cm/yr of convergence is accommodated at the Hikurangi Trough offshore the southern North Island, which decreases rapidly southward offshore the northern South Island (to a few mm/yr), where the majority of the relative plate motion is transferred onto strike-slip faults within the upper plate. This transfer of slip is facilitated via easterly-trending strike-slip faults (such as the Boo Boo fault in Cook Strait). Although the shallow megathrust offshore the northeastern South Island accommodates low rates of convergence, kinematic models based on geodetic data indicate that a large component of relative plate motion must be accommodated on the subduction interface at depth, down-dip of the major upper plate faults. This, along with geodetic evidence for interseismic coupling on the subduction interface beneath the northeastern South Island has implications for the potential southward extent of subduction interface earthquake rupture in central New Zealand. InSAR and GNSS evidence for large amounts of afterslip on the subduction interface following the Kaikoura earthquake also indicates the subduction zone continues as an important boundary well into the northern South Island.

Flexural bending of a downgoing subducting plate in response to forces from slab pull and topographic load leads to foreland basin development in front of growing mountain belts. Many foreland basins worldwide show along-strike variable basin architecture and subsidence history. Various factors such as lateral variations in slab pull, the presence of lateral crustal heterogeneity, slab breakoff and tear propagation have been suggested as drivers. However, the effects of an oblique continental collision on the evolution of foreland basins are largely ignored. In this study, we use 3D thermo-mechanical numerical models coupled with surface processes (i.e., sedimentation and erosion) to simulate an oblique collision. In the initial model, the continental plate margin is placed at an oblique angle relative to the subduction trench and we vary the following parameters: (1) margin obliquity, (2) convergence velocity, (3) age of the subducting oceanic lithosphere, and (4) presence of pre-existing rigid blocks in the subducting plate. Our results show that models with no obliquity (i.e., straight continental margin) create simultaneous along-strike continental collision and foreland basin subsidence. However, higher margin obliquity (≥ 15° ) causes a delay in the along-strike collision and foreland basin development. Our results suggest that the along-strike propagation of foreland basin development is controlled by the initial margin obliquity and plate convergence velocity. Finally, we discuss the implications of our study on the 3D evolution of the Northern Alpine Foreland Basin (NAFB) and intramountain basins within the Betics where along-strike variations of the sedimentary basin architecture are reported.

The Alps are one of the best studied orogens, but arguably also one of the most disputed ones. Several major geodynamic processes remain unclear, such as the mechanism of (U)HP rock exhumation, for example exhumation during plate divergence or syn-convergent exhumation, or the mechanism of subduction initiation, for example vertically forced initiation by gravitational sinking or horizontally forced initiation due to plate convergence. The Tibetan plateau is currently the highest continental plateau and its first-order geometry is well constrained. Spatial variations in topography and crustal thickness can be used to estimate horizontal forces per unit length from spatial variations in gravitational potential energy per unit area. Knowledge of forces and stresses is essential to understand geodynamic processes. However, maximal magnitudes of differential stresses occuring locally within the crust remain disputed and range from ca. 10 MPa to several hundreds of MPa. Deterministic mathematical modelling based on the fundamental laws of physics is one method to test different geodynamic hypotheses and quantify potential stress magnitudes. Here, we employ 2D petrological-thermo-mechanical numerical simulations to the Alpine orogeny to test the two hypotheses of horizontally forced subduction initiation and syn-convergent exhumation with a single simulation and with petrological and geochronological data. We use 3D mechanical numerical calculations for the Tibetan plateau, to quantify the impact of (i) a realistic double curvature of the Earth’s crust, (ii) the effective viscosity of the crust, (iii) the stress exponent of a power-law flow law and (iv) the plateau’s corner regions on the 3D crustal stress field.

Recent decades have been connected with an impressively accelerating pace in the development and availability of new analytical techniques to earth scientists. Interestingly, the smaller the scale considered, the more heterogeneous an apparently uniform rock sample is. This heterogeneity is not only characterized by variation in chemical composition but also in mechanical properties. The mechanical effects may influence element transport and mineral assemblage in rocks which can, in turn, significantly control the mechanical-chemical coupling rates and mechanisms of various processes in the Earth’s interior.

Considering the interplay of metamorphic reaction and mechanical properties in our quantification approaches is critical for correct interpretation of observations in metamorphic rocks. In my contribution, I will show major applications of the new quantification approaches, the accompanying obstacles and the consequences for our petrological interpretations. New findings from coupled experimental and numerical studies emphasize the necessity of quantifying the stress/pressure distribution before any complex thermodynamic interpretations. In fact, any thermodynamic interpretation of a stressed system must take into account the locally-resolved state of stress during sample deformation.

The grain-scale mechanisms of hydration of mafic lower crustal rocks are investigated on chemical maps of continuous rock sections (20 x 2 cm) of partially amphibolitized samples from the Hustad Igneous Complex in the Western Gneiss Region, Norway. The Proterozoic pyroxenite body and crosscutting dolerite dike enclosed in felsic gneiss that underwent (U)-HP metamorphism show different responses to the exposure to hydrous fluids along fractures formed during late Caledonian extension and exhumation. While the dolerite reaches full amphibolitization in a cm-scale reaction halo with a dm-scale transition zone, the pyroxenite has experienced previous metamorphism and is less affected by this event. Dissolution-precipitation reactions and slightly faster grain boundary assisted flow are identified as the main mechanisms of fluid flow through the rock. Limited element mobility is documented by grain-scale compositional gradients in forming amphibole from magnesiohornblende (Si_6.8, Al_1.6, Mg_3.0) to tschermakite (Si_6.4, Al_2.0, Mg_2.6) at boundaries with plagioclase. Phase diagram calculations yield a P/T-window between 650 – 730°C and 0.4 – 0.6 GPa for amphibolite formation. To better understand the mechanism of hydration, a numerical model of Darcy flow coupled to amphibolitization reactions was formulated based on mass conservation and local equilibrium. The simulations suggest the observed difference in front propagation distance is controlled by the main lithologies. A simple 2D model is employed to demonstrate that the gradual transition from dolerite to amphibolite can be achieved by implementing higher permeability along grain boundaries, supported by the observation that flow along boundaries continues before individual grains are fully replaced.

In the Southern Brasília Orogen (south-eastern Brazil), a nappe system that represents the roots of a magmatic arc records HT-UHT metamorphic conditions in lower to mid-crustal rocks. It is divided into two segments by a major shear zone, of which the northern nappe hosts the most extreme metamorphism and has been targeted for most petrochronological studies. These rocks carry insights into the stages of orogeny, as well as the first direct evidence of the paleo-active margin basement, and time-constraint (1) a metamorphism related to the magmatic arc consolidation on the active margin at 670-640 Ma and (2) an enduring UHT event related to collision and decompression at 630-590 Ma. The southern nappe (Socorro Nappe) hosts felsic and mafic granulites, and migmatites that apparently describe a less extreme pressure-temperature setting and relatively younger ages. We found distinctive patterns pertaining the inner nappe and its outward boundaries (Embu Terrane and São Roque Domain). We present new U-Th-Pb_C monazite data and LA-ICPMS U-Pb and Lu-Hf systematics in zircon retrieved from granulites, migmatites and paragneisses, and partial results on conventional thermobarometry and thermodynamic modelling. Our data plot within the P-T range of upper amphibolite to granulite facies and describe mostly post-peak retrograde clockwise trajectories, with lesser conditions at the nappe boundaries. Temperature, textural context and anatexis are major controls on the preservation of monazite versus zircon records. The outer nappe tends to host prominent 750 Ma-old monazite, whereas in the inner nappe such ages are scarce and most prevalent in the zircon records.

Although the burial of organic carbon in submarine fans and its importance for the carbon cycle have recently received growing attention, our understanding of the mechanisms at play is still lacking compared to other organic carbon storing environments.

Here, we present insights on the distribution of organic carbon throughout marine slope environments from the Arro System, Aínsa Basin (Spain). Evaluation of TOC content by C/S analysis from 82 samples show that there are distinct partitioning patterns of organic carbon between different depositional slope environments and mass transport complexes (MTC). Channel axes are relatively poor in organic carbon (average 0.1% TOC), while overbank deposits are relative enriched (average 0.49% TOC). Intraslope lobes show high variability between their sub-environments. Lobe axis deposits have an average TOC content of 0.13%, lobe fringe deposits 1.21% and the lobe distal fringe deposits 0.55%. Mass transport complexes have an average TOC content of 0.53 %. Integration of Hydrogen Indeces (HI) and T_max, established by RockEval analyses, points towards our samples falling within the range between Type III and Type II kerogen (terrestrial and marine matter), while δC¹³ show a range between 24.5 and 26.5‰, indicating a predominantly terrestrial source.

Our study shows the partitioning of organic carbon across slope environments that are dominated by different depositional processes. The understanding of this variability is important as wrong assumptions about carbon content can be made from studies that ignore spatial differences and potentially lead to false interpretations of climatic/tectonic changes and estimations on carbon budgets.

Provenance studies in the Central European Basin are challenged by the complex geology of source areas. The Variscan orogen represents a puzzle of Cadomian terranes, Variscan-aged domains and Palaeozoic sediments with Baltica-/Gondwana-derived detritus. The Caledonian-Fennoscandian source area comprises the Caledonian Belt, Archean to Neoproterozoic domains (Baltica), Variscan molasse sediments and Permo-Carboniferous igneous rocks.

The low-maturity Schilfsandstein (Stuttgart Formation), composed of first- and second-cycle sands, is an ideal candidate to evaluate provenance tools in a complex setting. Within a basin-scale study, subsurface facies maps, heavy minerals, and U-Pb zircon ages were applied to samples from Germany and onshore UK. Results show that the Schilfsandstein represents variable mixtures of recycled sediments and eroded basement. Heavy minerals are dominated by the Gt-Zr assemblage in North Germany (Fennoscandia), by the Ap-Zr-Ep assemblage in southern NW Germany (Rhenish Massif), and by Gt-Zr, Ap-Zr or Ap-Gt-Zr assemblages in Central and South Germany (Bohemian Massif, Vindelician Land). The clear discrimination of Variscan and Fennoscandian sources based on heavy minerals and subsurface facies maps is less constrained by zircon age spectra. Samples from North Germany either show a mix of Fennoscandian and Variscan spectra or typical Variscan spectra comparable to spectra of samples from Central and South Germany. The statistically identical age spectra of samples from North and South Germany (except UK) suggests mixing of source signals in Schilfsandstein rivers or recycling of Variscan molasse sediments in Fennoscandian catchment areas. The results show that complex source-to-sink settings need integrated approaches, individual provenance tools may lead to ambitious results.

We used original detrital zircon morphology, trace element, and U-Pb age data obtained from Upper Rotliegend II strata (Upper Permian) to reveal sedimentary fluxes within the Central German Basin. Understanding the evolution of such a system is crucial for further studies, given that the North German Basin is storage to vast natural gas resources and may also serve as an intermediary sedimentary repository for younger strata.

The detrital zircon dating results revealed the presence of main age clusters from the Permian, Carboniferous, and Cambrian periods. Additionally, several minor clusters from the Neo-, Meso-, and Palaeoproterozoic eras were also identified. These ages are remnants of the Cadomian and Variscan orogenies and the opening and closure of the Rheic Ocean. Zircon grain morphologies varied from completely unrounded to completely rounded grains across the age range. The heterogeneity of the data obtained from the studied mineral grains is vital to understanding the sedimentary history of the Central German Basin. It suggests that the basin fill is most likely a mixture of repeatedly recycled material and directly derived material from bedrock sources.

The detrital zircon trace element data support these findings, showing a wide range of values indicating different magma sources. These results underline the complexity of detrital zircon, and shed further light on the sedimentary history of the Central German Basin. We also found that the North German Basin is an integral part of a sedimentary recycling system spanning Central Europe, which is active since the Neoproterozoic.

The Paleoarchean Moodies Group (ca. 3.22 Ga) of the Barberton Greenstone Belt (BGB) is the oldest known well-preserved, shallow-water siliciclastic sequence on Earth. Proximal-to-distal textural and petrographic examination of selected units across adjacent terrestrial, coastal, and shallow-marine depositional facies of this strongly deformed unit provides the opportunity to constrain Archean weathering conditions by source-to-sink analysis, complementing previous bulk analyses. We examined conglomerate, sandstone, and shale composition by detailed geologic mapping and facies analysis along progressive downdip sediment routing systems, after excluding regions of syndepositional hydrothermal alteration. The majority of quartz and feldspar grains in the central BGB was sourced from intermediate to felsic intrusives and (sub-)volcanics of the Hooggenoeg Formation of the Onverwacht Anticline (OA). Downdip textural and mineralogical maturation from immature, F-, L- and matrix-rich, coarse-grained debris-flow-style units to texturally and compositionally supermature fine-grained sandstone occurs within a few km; facies belts fringe the OA. Chemical weathering and mechanical disaggregation of latite-dominated clast populations in proximal facies accompanied decomposition of F to clay (now partially preserved as sericite grains) and of intermediate volcanic grains to quartz-sericite-mosaic grains within a few km from their source. Energetic reworking in wide coastal-facies belts winnowed the abundant clay from the sediment and generated supermature sand, possibly aided by high tides. We deduce that Moodies Group sediment generation appears to have occurred in an aggressive weathering environment; in the coastal zone, only sediment which was silicified surficially and pre-compaction escaped transformation to a sedimentary “restite”.

A coordinated and effective use of the subsurface requires in-depth knowledge and easily accessible and uniformly described data. The 2022 Action Plan supports the securing of future investments in the subsurface through the provision of structured and harmonized digital geological data.

The efficient use of geological data in Switzerland is hindered by these factors: 1) Existing data sets are neither completely available in digital form, nor comprehensive, nor harmonized; 2) Uniform access to federal and cantonal data is lacking; 3) Information systems for 3D visualization and analysis of geological and non-specialist (geo-referenced) data are being developed.

In the future, the main benefit of geoinformation will be generated from the improvement of efficiency in the processing of existing data and from increased data quality, not from new products. The action plan starts here and defines these fields of action: Standards, Harmonization, Production and Access. In doing so, it is aligned with various strategies and policy areas. The digitalization called for in the action plan will facilitate the exchange and use of geological data and improve their availability. A coordinated approach with the most important national data owners is in focus, as is the use of new technologies.

The success of the action plan will be measured after completion by the state of digitization of analog archives as well as the achieved standardization, harmonization and completion of geological data and models throughout Switzerland.

The presentation will highlight the background, scope, ongoing implementation and future of the action plan using practical examples.

Der Beginn des systematischen, wissenschaftlichen Sammelns von Mineralen und Fossilien in Berlin ist eng verknüpft mit der Gründung der Berliner Bergakademie durch Friedrich II. Ab 1801 erhielt diese Sammlung die Bezeichnung „Königliches Mineralienkabinett“.

Mit der Gründung der Königlich Preußischen Geologischen Landesanstalt (KPGLA) 1873, der Integration der Bergakademie in jene wurde der systematische Aufbau des Probenarchivs - insbesondere in Zusammenhang mit der geologischen Kartierung Preußens und der Lagerstättenerkundung im In- und Ausland, inkl. der deutschen Kolonien forciert und es begann der Aufbau eines Geologischen Landesmuseums in Berlin. Ihrer Bestimmung nach dienten die Sammlungen in erster Linie als Archiv für das Belegmaterial aus der geologischen Kartierung und der wissenschaftlichen Erkundungsarbeiten. Der geschätzte Gesamtbestand umfasste 1939 ca. 1200 doppelseitige Schränke.

Nach erheblichen Verlusten des Sammlungsbestandes im 2. Weltkrieg, und der Abgabe von großen Teilen der im damaligen Ostteil Berlins befindlichen Sammlungen an das benachbarte Museum für Naturkunde durch die Staatliche Geologische Kommission der DDR hatte sich der Umfang der Sammlungen etwa halbiert. In den Jahren bis 1990 wuchs der Bestand wieder beträchtlich, insbesondere im Rahmen der intensiven und extensiven Rohstofferkundungen im Zentralen Geologischen Institut der DDR (ZGI).

Bei der Übernahme der Sammlungen durch die BGR 1990 lag die Anzahl der Schränke bei ca. 800. Seit 1996 sind die historischen geowissenschaftlichen Sammlungen sehr repräsentativ in Dienstbereich Berlin-Spandau in den ehemaligen Stallungen eines preußischen Kasernenkomplexes untergebracht. Die Digitalisierung und virtuelle Nutzbarmachung des umfangreichen Sammlungsbestandes für Wissenschaft und Öffentlichkeit stehen seither im Fokus der Arbeiten. Stand 2023 sind ca. 65 % des Bestandes online recherchierbar.

The search for saline water springs started in the area of Mecklenburg-Western Pomerania several hundreds of years ago. First drillings to find coals seams were reported from the end of the 18^th century. Mining for brown coal lasted from 1817 until 1960. Three mines produced between 1900 and 1926 potash and rock salt. First oil exploration wells were drilled in the 1920/30s without success. Numerous deep wells drilled between 1950 and 1990 reaching depths up to 8,009 m and about 3,600 seismic lines enabled the detection of several oil deposits. The huge amount of subsurface data allowed to find geothermal resources in the 1980s and is still the base for new scientific investigations and to develop projects of underground uses.

The archive of the Geological Survey of Mecklenburg-Western Pomerania comprises lithology data from 700 deep wells. More than 2,250 well logs exist, most of them are SP and GR logs. 70,000 m of cores from 400 wells document rocks from different eras beginning with the Mesoproterozoic basement of Baltica, covering the Caledonian deformed Ordovician on Rügen and the Devonian to Carboniferous strata of the Variscan foreland as well as the volcanics and sediments filling the North German Basin since the Permian. More than 11,000 rock samples and c. 26,000 thin sections used for petrographic descriptions are preserved. Countless analogue data gained from petrophysical and geochemical analyses still have to be digitized to fulfill the requirements of the Geological Data Act (GeolDG), especially for making geological data available for the public.

The Geological Archives (geoarchives) of State Geological Surveys have an over 150 years old tradition. Since the first geological surveys were funded in the early 1870s State Geological Surveys collected, inventoried and provided samples, maps and reports from geoscientific exploration and analysis. As a result, geoarchives comprise a huge store of knowledge for geologic surveying and further applied questions. Thereby, work tasks in geoarchives have special focusses: (1) In contrast to classical steady-state archives, the inventory must be permanently available and usable for geological surveys and economic companies. (2) All inventory can accurately be georeferenced, i.e. even documents must be assumed to contain geoinformation. (3) Geoarchives contain material, e.g. rock samples, drill cores on the one hand and printed reports, maps and paper rolls on the other hand, with a broad spectrum of requirements on the storage conditions. With the commencement of the Geological Data Act (GeolDG) these tasks were recently expanded to aspects of digitalization and digital provision of geoarchive inventory. Therefore, all material must be completely checked, categorized and indexed with keywords to make the inventory FAIR (findable, accessible, interoperable and reusable). In our contribution we present the historical evolution and relevance of the geoarchive of the Landesamt für Geologie und Bergwesen Sachsen-Anhalt (LAGB) and explain our recent concepts against the background of the GeolDG.

Im Rahmen der geologischen Landesaufnahme werden in Hessen, wie in allen anderen Bundesländern auch, seit weit über 100 Jahren wertvolle Gesteinsproben (Bohrkerne, Handstücke, Fossilien, Mineralien) gesammelt, beschrieben, analysiert und archiviert. So liegen aktuell alleine für das Gebiet Hessens über 45.000 Handstücke, mehrere 1000 Makrofossilien und ca. 700 Bohrungen vor. Der Öffentlichkeit bzw. interessierten Dritten stehen diese Archivalien zwar grundsätzlich zur Verfügung, jedoch stellen die bisher gegebenen Zugangsmöglichkeiten kein niederschwelliges Angebot dar. Im Zuge der digitalen Transformation sollen deshalb auch diese "unüblichen Informationsträger" digitalisiert und als 3D-Objekte funktional, performant und um weiterführende Informationen "angereichert" über das Internet abrufbar sein. Hierzu wird das Hesssische Landesamt für Naturschutz, Umwelt und Geologie (HLNUG) seit 2022 durch das Hessische Ministerium für Digitale Strategie und Entwicklung gefördert. Die Projektarbeiten adressieren sowohl die Erstellung von geologischen 3D-Objekten wie auch deren Visualisierung bzw. Veröffentlichung im Internet. Im Rahmen des Vortrages werden die bisherigen Bemühungen, der nunmehr präferierte methodische Ansatz und erste serienreife Ergebnisse vorgestellt. Dabei handelt es sich sowohl um Handstücke wie auch Bohrkerne. Auch wird das Konzept zur Veröffentlichung der erarbeiteten 3D-Objekte im Internet unter Berücksichtigung diverser Anwendungsfälle vorgestellt. Mit dem Vortrag möchte das HLNUG potenzielle Mitstreiter erreichen, sei es im Kreise der Staatlichen Geologischen Dienste oder auch Universitäten, wo die Digitalisierung der Lehre im Bereich der Grundlagenvermittlung auch und besonders bei den Geowissenschaften eine große Herausforderung darstellt.

Both the sustainable use of our resources and the prevention of geohazards requires reliable information about the spatial distribution of soil and geological properties. Since direct measurements are costly, artificial intelligence (AI) methods are used to estimate these attributes, leveraging a machine learning algorithm which relates laboratory measurements or expert class information to environmental covariates derived, e.g. from relief, geology and climate data. This study evaluates random forest (RF) as an AI technique to predict the occurrence of debris on slopes of the entire Black Forest in 10 m resolution. It also examines whether RF models can be applied to measured geogenic radon potential (GRP) for assessing the risk of possibly harmful radon concentrations inside buildings in Baden-Wuerttemberg.

A suite of 6770 expert class labels indicating whether hillside debris of at least 1 m thickness occurs or not, were associated with main geological classes and various terrain attributes obtained from a LiDAR-based digital elevation model. RF classification showed very good results with an accuracy rate of 86 %. GRP mapping is currently based on 580 radon measurements in soil gas at 1 m depth and a set of covariates comprising soil attributes, climate variables and geological data such as uranium concentrations. Preliminary results indicate that the GRP map generated by using a state-specific RF model is highly useful in identifying municipalities as vulnerable areas for which action is needed to mitigate this particular threat to human health.

The increasing digital provision of geological maps leads to a growing need for data harmonisation in order to make the data usable across borders. An essential prerequisite for this is the harmonisation of the geological general legends. Therefore, the main objective of the ConSent project was to establish interoperability between the existing large-scale geological map series (GK25/50) for the example of the federal states of Baden-Württemberg and Bavaria. Furthermore, the project is about the automated derivation of small-scale from large-scale geological maps. First, the geological general legends of the GK25/50 of Baden-Württemberg and Bavaria were implemented as hierarchical vocabularies in the thesaurus management system of BGR (RDF-enabled using standardised vocabularies based on semantic web concepts). The next step was to identify the greatest common denominator of the geological legends of the two federal states. This was done by an overarching geological general legend (OGL). Subsequently, the geological general legends of the two map series were linked semantically to the OGL using the SKOS vocabulary. Then, a merged GIS dataset of the GK25/50 was created containing the original geometries of both federal states. The polygons are attributed with both the original terms and the harmonised terms of the OGL. The harmonised map is publicly accessible via the project web application at BGR. Finally, the map was successfully generalised into three superordinate map scales (GK250, GK500, GK1000). The project shall be extended to other geological surveys.

The high-energy processes during the Elsterian glacial stage have formed a diverse relief of the base Quaternary with buried tunnel valleys, which are cut between a few tens of meters up to 400 m into the Tertiary bedrock sediments (Kuster & Meyer 1979). The Quaternary deposits host large groundwater reservoirs and are an important source for mining sand and gravel. The buried tunnel valleys also help to predict the erosion depth of future glaciations in the context of finding a site for a repository for radioactive waste in Germany. Therefore, it is crucial to provide a comprehensive geological model of the base Quaternary in order to support planning strategies in sustainable resource extraction and land use.

Kuster & Meyer (1995) published a contour map of the base Quaternary in Lower Saxony. Since then a vast number of new datasets were obtained. We started modelling a 3D surface based on these new datasets and the original contour map by Kuster & Meyer (1995) using SKUA-GOCAD™ (AspenTech). Here, we are presenting the first completed sub-region of this model, pointing out both the major advances that we achieved by integrating new borehole and seismic data (2D/3D) as well as the challenges of data harmonization. We were able to identify tunnel valleys that were unknown before and to revise the geometry and depth of known subglacial channels. The depth of the base Quaternary was adjusted by up to 150 m in certain areas.

Mapping the Quaternary base is required for various processes. Accordingly, it serves as a necessary horizon for set-up of 3D geological models of the subsurface, as well as a database for engineering geological processes. The most important field of application in Brandenburg considers hydrogeological questions such as the separation of the freshwater/ saline-water level in aquifers. Reliable and detailed working basis are needed for sophisticated modelling and to ensure the integration of all different data and information leading to area-wide maps.

At the geological survey of Brandenburg data of more than 200 000 drillings (from the beginning of 1900 until today), seismic profiles (average profile density of 0.7 km/km²) and gravimetric measurements (average point distance of c. 5 km) are available. In recent years maps of the Quaternary base were constructed independently by specific tasks and requirements. As a consequence, ten different maps were produced in the period from 1970 to 2014. Scaling varies between 1:10 000 to 1:1 000.000, while those with the higher resolution cover only parts of Brandenburg. The aim of this study is to combine all datatypes to create a holistic model, which can be used interdisciplinary. The varying quality and quantity, as well as the large age range of the incoming data pose a challenge being solved with different modelling approaches and geostatistical methods.

The Geological Data Act (GeolDG) came into force on June 30, 2020. It has replaced the Mineral Law (LagerstG) and has lead to a comprehensive new legal regulation in the field of recording, archiving and publishing geological data. The primary objectives of the Act are to safeguard geological data and make it available to the public, to ensure the sustainable use of the geological subsurface, and to be able to identify and assess geohazards.

Therewith it also affects clients of geological investigations and those commissioned to carry them out, e.g. drilling companies, etc. There is an obligation to notify the competent authority of all geological investigations at least two weeks before they begin. Data transmission and public provision is also regulated by means of deadlines. The term "geological investigation" includes all general geological, raw material geological, engineering geological, geophysical, mineralogical, geochemical, pedological, geothermal, hydrogeological and geotechnical measurements and recordings of earth's surface, geological subsurface, of ground or groundwater, obtained by means of prospecting, drilling, field or borehole measurements and other exploration methods such as remote sensing, as well as the processing of the data obtained in this way, as well as analyses and evaluations of these data, e.g. in the form of expert reports, surveys, and reports.

With the contribution here the law is presented fundamentally and for the execution of the law announcement procedures in the countries as well as processes of data transmission and administrative procedures for data supply.

Over the past 30 years, our knowledge of Cretaceous stratigraphy and timescale has expanded exponentially. This has been based partly on the greater refinement of biostratigraphy, including the utilisation of groups of fossils previously poorly known or ignored (microcrinoids, inoceramid bivalves, diverse microfossil groups) and also the development of geochemical and geophysical stratigraphies, most notably stable carbon isotope- and magnetostratigraphy. These two methodologies have enabled previously impossible correlations to be made, independent of facies and sometimes in the absence of biostratigraphical evidence. The identification of orbital cycles in Cretaceous sediments, integrated with new radiometric dates, now provides a high-resolution timescale for intervals of the Cretaceous. Work continues apace to extend and refine the timescale and integrate this with new stratigraphical data. Additionally, data generated primarily for the purpose of correlation, such as stable carbon isotope curves, provide direct evidence of the Cretaceous carbon cycle and allow a better understanding of palaeoenvironmental changes.

Until very recently, it was generally assumed that the marine flooding of the Saxonian Cretaceous Basin (SCB) was largely related to the naviculare Transgression of the early Late Cenomanian. However, based on the detailed investigation of 39 Cenomanian sites at surface and subsurface, and considering new macrobiostratigraphic data and existing palynological facts, a completely revised integrated stratigraphic framework and palaeogeographic reconstructions of the lower Elbtal Group are presented (Niebuhr & Wilmsen 2023, ZDGG 174, DOI: 10.1127/zdgg/2023/0376). Demonstrably, Cretaceous sedimentation started already in the early Early Cenomanian, indicated by the contemporaneous onlap of non-marine (Niederschöna Formation) and marine strata (Oberhäslich Formation). The Cenomanian transgressions advanced from the north, at first following the course of roughly south–north-discharging palaeovalleys of a fluvial palaeodrainage system. Sequence stratigraphic analyses demonstrate the presence of four complete, unconformity-bounded Cenomanian depositional sequences (DS) and a fifth one, DS Ce-Tu 1, which started in the mid-Late Cenomanian and lasted into the Early Turonian. The depositional sequences comprise five major transgressive phases that overstepped each other, culminating in an earliest Turonian climax of the 2^nd-order Cenomanian transgressive hemicycle. The maximum thickness (100–120 m) equates to the accommodation generated by eustasy and regional subsidence during the entire 6-myr-long Cenomanian age (sedimentation rate ≤20 m/myr). Thickness changes within the lower Elbtal Group can quite simply be related to pre-transgression topography and sequence stratigraphic onlap patterns. Thus, the new stratigraphic and palaeogeographic framework of the lower Elbtal Group also demonstrates that tectonic inversion in the SCB was essentially a post-Cenomanian process.

The Oxfordian period is characterized by a long-term (ca. 6 Myrs) trend of increasing stable carbon isotope values, punctuated by three short-lived (ca. <1 Myrs) carbon isotope excursions (CIEs) at the Callovian/Oxfordian boundary, in the lower Oxfordian (Quenstedtoceras mariae ammonite zone), and in the middle Oxfordian (Gregoryceras transversarium ammonite zone), also known as the MOxE. This pattern is evident worldwide in both organic and inorganic carbon (δ¹³C_org and δ¹³C_carb) in terrestrial and shallow marine environments, indicating recurrent global carbon cycle disturbances affecting the entire ocean-atmosphere system. However, previous sedimentological and chemostratigraphic studies on Oxfordian strata in the Lower Saxony Basin (LSB) of northern Germany, have failed to identify the three CIEs cited above, hindering their correlation with the global carbon isotope record. In this study, we provide, for the first time, a high-resolution δ¹³C_carb record revealing the MOxE expressed in a positive CIE of 3.8‰. We collected data from drilling core samples of the Korallenoolith Formation in the Konrad 101 borehole, located in the southwestern part of the LSB. This exploration drilling is biostratigraphically well constrained, unlike many other sections in the LSB that are characteristic of shallow tropical marine depositional settings. This particularity enables us to compare the Konrad 101 δ¹³C_carb pattern with other localities distributed worldwide incl. Europe, western Asia, and the Gulf of Mexico. Our high-resolution δ¹³C_carb reflects a major synchronous change in the exogenic carbon cycle, with no satisfying explanation so far for the triggering mechanisms, in the context of already published datasets.

The biostratigraphy of the Jurassic system has made many advances in recent years. We can distinguish over 50 successive faunal horizons in the Callovian, which corresponds to a resolution of perhaps 75,000 to 100,000 years. The distribution of the ammonite genus Kepplerites in space and time has been extensively studied. This example illustrates the importance of a precise stratigraphy for paleontological and sequence-stratigraphic questions.

The beginnings of the ammonite genus Kepplerites can be traced back to the Subboreal sea of NW Canada in the late Bathonian (Middle Jurassic). Thereafter the evolution can be followed over Greenland, the Russian platform over the Caucasus to Central Europe, up to its abrupt extinction at the beginning of the Callovian. Only a small population survived, probably in what is now the Caucasus. From here, a few specimens reached Central Europe and the Russian platform, where new species emerged (genetic drift). At the beginning of the Koenigi Zone, a species migrated from Russia via the Caucasus to Central Europe, where they mixed again. From this, separate lines developed in England and Central Europe (gradualism), the seas of Greenland were also settled again. At the end of the Koenigi Zone, Russian species immigrated again and replaced the weakened populations in Central Europe and England. By the end of the Early Callovian, all sea straits were open and a unified Subboreal faunal province of NW Europe, Greenland and the Russian Platform was established. This scenario was controlled by sea level rises and falls and short-term climatic changes.

Aalenian sedimentary deposits in southern Germany have accumulated in a shallow-marine, epicontinental shelf environment. These accumulations are dominated by thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top. Aalenian sediments are likely to represent a relatively complete stratigraphic record, however, the sedimentary evolution and paleoclimatic significance of these typically poorly exposed deposits remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany to identify Transgressive-Regressive cycles during the Aalenian stage. Results are based on three scientific drill cores of 200 – 250 m length that have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval (10 keV, 500 µA). Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework for the thick and largely homogenous lower Aalenian Opalinuston Formation.

In Central Europe, the about 1 km thick Buntsandstein was deposited in the large intracratonic Central European Basin (CEB). The Buntsandstein sedimentary succession displays a striking cyclicity of varying magnitude. The most obvious cycle is the 10 to 20 m thick small-scale cycle (wet-dry cycle) that is ascribed to changes in lake level (base-level) and assumed to be controlled by astronomical forcing of climate.

Combined with wireline logs, these cycles can be mapped over large parts of the Central European Basin providing a high-resolution cyclostratigraphic framework. Hence, the cycles represent basin-wide events. The isochronous character of this framework has been proven by magneto- and biostratigraphic means. The detailed magnetostratigraphy spans the upper Zechstein to lowermost Muschelkalk. Compared with available radioisotopic ages for the base and top of the marine Early Triassic, a Buntsandstein duration of about 6 Ma is derived.

Within the more central part of the CEB, the synchronous character of the cyclostratigraphic framework has been proven by magnetostratigraphic and biostratigraphic means. Based on an integrated comparison, radioisotopic ages obtained from Tethyan sections, have been referred successfully to the Buntsandstein cyclostratigraphy, substantiating the hypothesis that the pronounced small-scale cycles correspond to solar-induced ~100 ka eccentricity cycles. Hence, the duration of the Buntsandstein has been calculated to span some 6 Ma. The Buntsandstein cyclostratigraphy offers good potential to constructing a reliable astronomically calibrated Early Triassic geomagnetic polarity timescale.

Time indications in the Rotliegend Group of Germany are integrated and presented in a new way (Menning et al. 2022, ZDDG 173: 3–139). (1) U-Pb CA-ID-TIMS radio-isotopic age determinations from the Thüringer Wald (Lützner et al. 2021, Int. J. Earth Sci.), (2) the recalculated Rb-Sr age for the Donnersberg-Formation of the Saar-Nahe Basin (Menning et al. 2022) utilizing the recently revised ⁸⁷Rb decay constant (Villa et al. 2016, Geochim. Cosmochim. Acta), (3) the newly calculated mean age for the U-Pb SHRIMP data of Breitkreuz & Kennedy (1999, Tectonophysics) of 298.6 ± 1.9 Ma for the Central European Basin (CEB), which reduces the time span for the Altmark Subgroup volcanic succession from 302–290 Ma to ≈ 300.5–296.5 Ma, (4) the Re-Os age of 257.3 ± 1.1 Ma for the Kupferschiefer (base Zechstein Group), (5) the age of ≈ 265 Ma of the Illawarra Reversal of the Earth´ magnetic field, and (6) highly different palaeomagnetic properties of the sediments of the underlying Müritz Subgroup and the hanging Havel Subgroup are significant evidence for an extensive stratigraphic gap or a very gap-rich time span (≈ 295/293.5–266 Ma = Middle Rotliegend). In Central Europe, this gap forms part of the longest Phanerozoic time span without significant marine layers (≈ 311 Ma to ≈ 257.3 Ma = ≈ 54 Ma). The gap is most probably related to the amalgamation and the associated immense uplift of Pangaea in Central and Western Europe and thus termed the ‘Pangaea Gap’.

The Global Time Scale of the International Commission on Stratigraphy includes subdivisions of systems down to stages but substages can be recognized once all stages are ratified. Devonian substage progress slowed down since the inevitable Pragian/Emsian boundary revision has not yet been achieved. Formal substage definitions are urgent since variable versions are used widely, in different regions, and by different authors. This hampers the precise correlation of climatic changes, sea-level fluctuations, geochemical cycles, rates of evolution, and extinction/radiation events. Precise and unequivocal time-scales are the pre-condition for advances in multidisciplinary Earth System research and geological mapping. Our recent studies led to progress in the case of Givetian to Tournaisian substages, which all shall be placed close to 2^nd/3^rd order global events, which importance is often hidden by their timing within stages.

The future Upper Givetian base shall be placed at the top of the global Taghanic Crises (base of hermanni Zone) while the Lower/Middle Frasnian boundary should coincide with the anoxic Middlesex Event. The best boundary marker, Ancyrodella nodosa, provides correlation with the Alamo Impact of Nevada. Revision of the controversial conodont scale at Martenberg, a potential GSSP, confirmed the semichatovae Transgression (nasuta Subzone) as the best Upper Frasnian base. Other Rhenish sections are suitable for the definitions of the Middle (base marginifera Zone, Beringhauser Tunnel), Upper (Lower Annulata Event, Effenberg), and Uppermost Famennian (e.g. Oese, base ultimus ultimus Zone). The anoxic Lower Alum Shale (base crenulata Zone) should re-define a Middle Tournaisian substage following the classical Belgium chronostratigraphic scale.

The distinction between sedimentary and tectonic processes in the formation of chaotic rock units is especially difficult in orogenic belts, where sedimentary structures are usually strongly overprinted by tectonic deformation (e.g. Fiesta et al. 2019). This also applies to the chaotic rock units, which are widespread in the allochthonous domain of the Harz Mountains. For these units, it has been assumed that their chaotic rock fabric was initially sedimentary in origin and was merely tectonically overprinted by subsequent Variscan deformation (e.g. Schwab & Ehling 2008). In contrast, it could be shown, that tectonic processes were crucial for the formation of the chaotic rock fabric (Friedel et al. 2019). This is particularly evident in the structural characteristics of Devonian limestone blocks.

In chaotic units, blocks of (hemi)pelagic condensed limestone of different Devonian age are widely incorporated in a slaty-clayey matrix. So far, the blocks were mostly regarded as olistoliths and thus considered as clear evidence for a sedimentary origin of the chaotic rock units (olistostromes). However, our investigations show that the limestone blocks are fault-bounded, folded and internally imbricated stacks of limestone strata, whose final fragmentation and isolation occurred subsequently to tectonic folding.

Such blocks of fault-bounded imbricate stacks of rock strata are a diagnostic field-criterion to identify a strong tectonic overprint or even a tectonic origin of chaotic rock fabrics. Since such blocks are regionally distributed, they support, together with other structural features, a predominantly tectonic origin of these units and argue against widespread submarine mass-flow deposits.

References:
Fiesta et al. 2019, Gondwana Research, 74, 7-30
Friedel et al. 2019, Intern. Journal of Earth Science, 108, 2295-2323
Schwab & Ehling 2008, Karbon, 110-140; in Bachmann et al. (Hrsg.) Geologie von Sachsen-Anhalt, Schweizerbart

The Rhenish Slate Mountains are one of the classical outcrop areas for stratigraphic research in Devonian and Carboniferous strata. Lithostratigraphic mapping of German parts of the Rhenish Slate Mountains has been performed systematically for over 100 years starting with a mapping campaign implemented by the Prussian Geological Survey in the 1920s. Today, geological mapping is performed by the Geological Survey of North Rhine-Westphalia and published in an output scale of 1 : 50 000. Results are made available via a modern geodata infrastructure for the use by digital map display. We present sedimentological facies models for the time spans of the Middle to Upper Devonian and the Mississippian. On the one hand the lithostratigraphic lexicon LithoLex is the data source of definitions of lithostratigraphic units and on the other hand results of field mapping are needed to classify lithostratigraphic units that are not yet implemented in the lexicon. Our models can work as links between results of field mapping of the northern Rhenish Slate Mountains east of the river Rhine and help to classify lithostratigraphic units, where it is still needful.

Regular stratigraphic alternations in lower Paleoproterozoic iron formations (IFs) from South-Africa and Western Australia were recently linked to Milankovitch forcing (1, 2). Hence, valuable information may potentially be obtained from these ancient marine deposits about early Solar System dynamics and astronomical-forced climate change when Earth System was operating in fundamentally different ways compared to present-day and the Phanerozoic. In particular, the dominant imprint of long-period eccentricity observed in the Kuruman IF from South-Africa (2) implied a primary influence of climatic precession, while clear precession-scale variations were unfortunately not encountered in this unit. A clear and consistent expression of precession and eccentricity, however, is essential to investigate the climatic-environmental response to the precessional forcing directly, and to determine the precession frequency as to potentially constrain past Earth-Moon dynamics. Here we report results of cyclostratigraphic analysis and high-precision U-Pb dating of the 2.46-Ga Joffre Member of the Brockman IF, Western Australia, revealing exceptionally regular precession- and eccentricity-scale alternations identified in both outcrop and core. Based on the thickness ratio between the precession- and short eccentricity-related alternations seen in outcrop, we estimate a significantly shorter precession period at the time of deposition of the Joffre Member, translating to a shorter Earth-Moon distance and length-of-day (3). In addition, based on detailed geochemical analysis and modelling of the precession-related cycles identified from core, we present a first-order climate interpretation with possible implications for the redox evolution of the ocean-atmosphere (4).

(1) de Oliveira Rodriguez et al. 2019; (2-4) Lantink et al. 2019; 2022; 2023.

This talk presents a multi-method approach to construct a conclusive new correlation model for Neoproterozoic glacial units of southern Namibia. Therefore, ten different sections and a variety of samples were studied and analysed with respect to field relationships, whole-rock geochemistry, zircon U-Pb dating and Th-U ratios, Hf isotope measurements and zircon grain size analyses, combined with LA-ICP-MS U-Pb dating of cap carbonates.

Our analyses show that (1) sediments deposited during four Neoproterozoic glacial events in southern Namibia all have very similar detrital zircon characteristics, allowing the interpretation of continuous recycling of the same material over the most part of the Neoproterozoic, which is also supported by the whole-rock geochemical analyses, (2) cap carbonates can be analysed for their U-Pb isotope ratios and provide valuable age determinations, if reset and overprinted areas are recognised and avoided for laser ablation, (3) proving the Sturtian and the Marinoan age for the Numees Fm and the Namaskluft Mbr by U-Pb dating their overlying carbonate sequences was finally possible, (4) the Witvlei Grp sedimentation ends at 579 ± 52 Ma, which is the age of the stromatolites of the Okambara Mbr, representing the uppermost deposits of the Witvlei Grp, and this leads to (5) the onset of the Nama Grp sedimentation for southern Namibia is no earlier than 579 ± 52 Ma.

Mud-rich successions can be challenging to interpret accurately, since sedimentary structures such as cross-bedding and ripple marks are often scarce or absent. This makes it difficult to determine the exact environmental and depositional parameters. In order to gain a better understanding of the conditions of such environments, this study aims to compare two of the most important roofing slate deposits in Europe: The Devonian-age “Mosel Slates” and the Ordovician-Silurian-age Truchas Domain.

Until 2019, Rathscheck Schiefer mined the “Mosel Slates” from the Katzenberg mine in the SE Eifel, while companies such as Samaca actively exploit roofing slates near Valdeorras, making Spain one of the largest exporters of roofing slate. These slate mines provide a unique opportunity to gather new insights into the geology of the areas of Mayen (Rhenohercynian Basin) and Valdeorras (Truchas Basin). Both of these areas contain sediments which were deposited in marine shelf settings, although the precise mechanisms of deposition and the precise depositional environment are poorly understood.

This study presents the results of high-resolution facies analyses, both above and below ground, geochemical analyses, including XRD, XRF and CNS measurements, and micro-CT measurements of framboid populations. In both settings, deposition occurred in a low-energy regime on a passive continental margin. Sediments were derived and reworked from the Laurussian and Avalonian continents, respectively. Background sedimentation and density flows were the main mode of deposition. The water column was oxygenated and anoxia was restricted to the sediment in the “Mosel Slates” and to dysoxic episodes in the Spanish slates.

Milankovitch forcing exerts a major control on climate that is recorded in the sedimentary rock record. However, its influence on hyperpycnal flow sedimentation is largely unknown. Hyperpycnites, sediments resulting from hyperpycnal flows, which are related to climate through flood frequency and magnitude, may be valuable tools for understanding aspects of Earth’s paleoclimate. Their origin and distinctive layering have been explained by various mechanisms, including frequency of river breaches, sudden increase in the global hydrological cycle, sea-level fluctuations, and variations in sediment supply. Their potential link to paleoclimate variations commonly remains unexplored in detail. Here we use cyclostratigraphic analysis combined with published high precision U-Pb dating to investigate the influence of Milankovitch forcing on their deposition. A continuous drill core of the ~125-million-year-old Early Cretaceous Laiyang Formation (eastern China) reveals well-defined cyclic hyperpycnal flow patterns. The radioisotopic dating and magnetostratigraphy constrains the formation’s average sedimentation rate, and links the observed cycles to precession, obliquity and mainly orbital eccentricity cycles. Orbital parameters most likely paced the delivery of the hyperpycnal flow sediments mainly by river- and delta-supplied currents from non-marine basin immediately; we conclude that Milankovitch cycles exerted a primary control on hyperpycnal flow sedimentation. Sediment accumulation rates determined from 400 kyr cycle age model show a trend of decreasing and then increasing throughout the Laiyang Formation, which was synchronized with the evolution of sedimentary environment controlled by tectonic activity. This study shows that orbitally-induced climate change can also acted as principle driver on deep-marine terrigenous sediment accumulation within a tectonically active basin.

The expression “Rock+Acid+Water -> Clays+Ions+Bicarbonate” may seem simple, but it encompasses many complex processes working in the Earth’s Critical Zone (CZ). The SE United States Calhoun CZ Observatory (O) has been observing the CZ for decades, leading to new understanding of how geological and human factors impact landscape evolution and management. The distribution of clays in the CZO is linked to the response of land to various factors that influence soil formation. These factors include vegetative cover (such as crops, regenerative pines, and old-growth hardwoods), interfluve order (old ridge-crests versus young legacy sediments), underlying geology (felsic versus mafic rocks), climate change (wetter versus dryer seasons), and denudation rates (erosion rates ranging from 1 to 1000 m/Ma).

Through observations, we have found that plant cover and rooting depth affect soil gas (CO₂ and O₂) distributions, which in turn affect clay mineral hydrolysis and redox reactions. We have also found that clay mineral signatures show increasing indices of chemical alteration along increasing interfluve orders. Additionally, felsic rocks weather more deeply into the CZ than mafic rocks under similar biota, climate, relief, and time conditions. Furthermore, we have found that the chemical signatures captured in clays may not reflect average conditions, but rather specific points in soil moisture states. Finally, we have observed that rates of material transport within the CZ vary greatly depending on the chronometer used. The CZ constitutes a small volume of the Earth’s clay budget however it is an important clay factory in exogenic cycles.

Deeply weathered soils are iconic components of the tropical critical zone. Being short of exchangeable nutrients, physical features beyond sheer depth determine more than elsewhere the provision of life-sustaining resources. Biogeochemical models can hardly capture tropical fluxes, due to them being mainly developed and validated for temperate zones, focusing more on topsoil processes. To overcome this systematic bias, pedotransfer functions are regionally adapted for modeling soil water movements and then used for tropical biogeochemical modeling. However, soil texture based on single grain size distribution neglects the impact of actual soil structures in the field and leads to pronounced discrepancies between field measurements and model predictions for tropical soils. A prominent example of this mismatch is overestimated N₂O emissions.

Now, scientific efforts are being made to correct this systematic bias in predicting soil functioning. A well-known characteristic of tropical soils, potentially responsible for the systematic error, are water-stable aggregates called pseudo-sands. In the field, they are perceived as sand, but in the lab measured as clay and silt. The simple assumption that pseudo-sands act just like sands in the field seems to work satisfactorily for certain hydrological predictions. We pursue the hypothesis that, biogeochemically, pseudo-sands do not simply act like sands. We provide evidences why pseudo-sands cannot be simply treated neither like “regular sand” nor like the sum of its units. The long-term goal is to develop tropical biogeochemical model versions related to the properties of pseudo-sands that will lead to improved models of the critical zone of the tropics.

This contribution uses a recently published global clay mineral inventory of the critical zone to assess how well clay mineral assemblages reflect climate. The relative abundance of the main clay mineral groups (the 1:1, 2:1 and 2:1:1 hydrous phyllosilicates are used to evaluate a Clay Mineral Alteration Index (CMAI), which is compared with current latitudes and the Köppen-Geiger climatic zones. This CMAI relationship is defined as:

CMAI = (2:1LE + 2:1:1LE) – (1:1LE + 2:1HE)

(physically weathered – newly formed)

where, LE = Low to no expandability, HE = high expandability and CMAI values range between -100 (warm tropical) and +100 (cold polar).

For selected soil types, such as the alfisols, some general correlations exist between CMAI values and distance from the equator. However, the database indicates that lithological controls on clay mineral assemblages introduce a large degree of heterogeneity to the system. This makes a direct interpretation based on numerical indices difficult to implement. Improved correlations can be achieved by selecting consistent soil types developed on the same host lithologies (e.g. soils on Silurian shales). Following this procedure, very good correlations can be attained as long as the climatic parameters of temperatures and rainfall are both considered. A refined correlation between the CMAI and current climatic conditions is put to the test on palaeosols and shales from the geological record.

The depth of the critical zone, the zone that spans from the canopy to the weathering front in the subsurface, is mostly unknown due to its inaccessible nature. To identify the depth of the critical zone and infer its assumed control by water flow we conducted four drilling campaigns in granitoid rock along a climate gradient in the Chilean Coastal Cordillera. The drilled cores differ in the depth of the weathering front between arid, semi-arid, mediterranean, and humid climate. The arid study site is located at the southern end of the Atacama Desert and the drill core is hydrothermally overprinted. No chemical top-down weathering or physical disintegration of the granitic rock is found. The semi-arid drill core reveals multiple weathering fronts along fractures and shows top-down chemical weathering in the uppermost 10 m. In the mediterranean study site, we found the deepest weathering front with saprolite to a depth of ~45 m, followed by bedrock with wide fractures. The physical disintegration is stronger than chemical mass losses due to weathering. The humid study site is characterised by a shallow weathering front at ~10 m depth. Even though sufficient water is available to form a deep weathering zone, the formation of clay and other secondary minerals inhibits further advance of the weathering front by clogging pore space thus preventing water flow. We conclude while the of degree of (chemical) weathering is set by climate, the depth of the weathering front depends on the abundance and width of tectonic fractures.

In times of accelerated global change, integrated tools are urgently needed that allow process-based, quantitative assessment of how climatic drivers interact with land cover, soil water conditions and hydrogeology to control the inter-relationships between water fluxes and storage in the Critical Zone (CZ). These dynamic relationships determine the availability and quality of water resources during droughts at multiple spatial and temporal scales. This talk will present approaches to investigate the relationships between water fluxes through and storage in the CZ, together with the associated water ages and residence times. The focus will be on groundwater recharge, as groundwater levels have been dramatically affected by the recent extreme droughts in large parts of Central Europe. Multiple ecohydrological processes and transformations within the CZ are influencing groundwater recharge by partitioning incoming precipitation into green (i.e. evaporation and transpiration) and blue (i.e. groundwater recharge and streamflow generation) water fluxes.

Water stable isotopes help to constrain ecohydrological process understanding in the CZ. Incorporating isotopes into tracer-aided ecohydrological models allows water flux, storage and age dynamics to be quantified in both plot und catchment scale modelling. Using such novel analysis of the spatio-temporal interactions of water flux-storage-ages in the CZ improves understanding of the sensitivity and resilience of catchment functionality to hydroclimatic perturbations, and provides science-based evidence on which land management techniques have the potential to modify green water fluxes and to conserve soil water storage, to guide decision-making and build resilience to future droughts.

Streams are integrators over all biogeochemical reactions taking place in the Critical Zone. The resulting export of dissolved elements from a watershed is commonly used to infer chemical weathering fluxes. Yet, this approach rests on the assumption that the mass of a given element released from primary minerals that was not incorporated into secondary solids is quantitatively transferred into the stream in the dissolved form. The comparison of element-specific solute stream fluxes with chemical weathering fluxes determined in the residual solids shows that this is often not the case. An imbalance persists even after correcting for a bias potentially introduced by changes in water flow over these entirely different timescales.

To explore causes for imbalances between short-term and long-term weathering fluxes, described by their ratio in form of a “Dissolved Export Efficiency” (DEE), we sampled six Critical Zone water compartments for one year in the Conventwald (Black Forest, Germany). We found deficits in the dissolved load, which emerged in the deep saprolite. For Si, Al, and Fe the deficit can be attributed to an export pathway that includes a “hidden” Critical Zone compartment or pool of unsampled colloids that are exported preferentially during flushing events. In contrast, deficits found for nutritive elements (Ca, K, Mg, P) can be explained by deep nutrient uptake followed by nutrient retainment in re-growing forest biomass or export in form of biogenic particulates. Given the collective evidence for these imbalances the deep Critical Zone warrants attention towards a complete budget of element cycles.

Silicate weathering sequesters CO₂ from the atmosphere and stabilizes Earth’s climate over geologic timescales. In turn, weathering of accessory carbonate and sulfide minerals is a geologically relevant CO₂ source. Rock-uplift and -erosion is the primary mechanism by which fresh minerals are exposed to weathering at Earth’s surface. Therefore, the global inorganic carbon cycle is sensitive to mountain uplift and erosion. However, quantifying this sensitivity is complex, because existing data do not consider weathering of all relevant mineral phases, and because co-variation of multiple environmental factors obscures the role of erosion. Here, we analyze the sensitivity of silicate, carbonate, and sulfide weathering fluxes to erosion in solute chemistry from four small mountain streams that span well-defined erosion-rate gradients in relatively uniform metasedimentary lithologies. Across all datasets and 2-3 orders of magnitude of erosion rate, we find that silicate weathering fluxes are almost insensitive to erosion at rates >10^-2 mm yr^-1. In contrast, weathering fluxes from sulfide and carbonate minerals increase sub-linearly with erosion. By fitting a weathering model to these data, we show that the contrasting sensitivities of silicate, carbonate, and sulfide weathering produce a distinct CO₂-drawdown maximum at moderate erosion rates of ~0.1 mm/y. Below this maximum, mineral supply limits silicate weathering. Above the maximum, silicate weathering fluxes plateau and CO₂ emissions from coupled sulfide oxidation and carbonate weathering increasingly dominate the carbon budget. Overall, uplift of metasedimentary lithologies to moderate relief can substantially bolster Earth’s CO₂ sink whereas further uplift may decrease, or even reverse, CO₂ sequestration rates.

Ferricretes are hard iron layers forming in semi-arid to subtropical environments. We can observe them in i.e. Africa, Australia or Brazil. They are an important part of regional geomorphology, capping hills and protecting landscapes. Climatic dependance is very high. Ferricrete formation occurs under strongly seasonally contrasting climates with precipitation and dry cycles. During wet seasons, transport and accumulation of elements happens while during dry seasons, precipitation and hardening dominate. It is also known that ferricretes form in tectonically “quiet” environments, and approximately need 1 Myr to form meter thick layers.

There are two ferricrete formation hypotheses, the hydrological hypothesis and the laterite hypothesis.

Recently, we developed a numerical model for ferricrete formation based on the laterisation hypothesis. 33% of land surfaces are covered by laterites today. The thickest lateritic profiles evolved for millions of years and are found in the centre of tectonically inactive areas. Weathering is the main process responsible for laterisation, transforming bedrock into regolith. A typical lateritic profile is divided into multiple stages from the weathering front to the surface, starting with a coarse grained and then fine grained saprolite, a mottled zone and at the top, a ferricrete.

In our model, we assume that as the regolith ages, it undergoes a process of transformation that leads to hardening and compaction. Material is constantly eroded away from the regolith, thus making the model dependant on a constant material input for example through uplift. This is necessary to reach sufficient laterisation levels for ferricrete formation.

Land-ocean interactions in the coastal zone are of particular interest regarding the exchange of substances, like nutrients, carbon, sulfur, metals, and water. The rising sea level is and will enhance the pressure of salty solutions on previously fresh water ecosystems. Currently coastal areas in the North Eastern part of Germany under increasingly rewetted by the connection with the brackish Baltic Sea. We present results on the isotope biogeochemistry of a modern rewetted wetland, at the southern Baltic Sea, the Huetelmoor, that is under impact by event-type flooding by brackish seawater. These events lead to an enhancement of sulfate availability for microbial carbon transformations. Sediment cores on transects within the wetland were investigated for the pore water and soil composition, together with selected ground water wells and surface waters from the channeling system. Different fractions of the soils were analyzed for the elemental composition, mineral micro-textures, and the stable sulfur (and oxygen) isotope composition of different sulfur fractions to understand the water and biogeochemical carbon-sulfur-metal cycles and the geochemical signatures in authigenic mineral phases and organic matter. Adding sulfate creates space for mineral authigenesis and organic matter sulfurization. The soils are impacted by different intensities in sulfur cycling as reflected by isotope and textural signals. Further mechanistic investigations consider the role of DOS upon changing sulfur substrate availability. Results allow for a transfer of proxy information to other modern and past coastal organic-rich peatlands.

Acknowledgement for support by DFG Research Training Group BALTIC TRANSCOAST, ERASMUS, and DAAD