Deep geological repositories for radioactive waste rely on geological barriers to isolate waste and impede or limit radionuclide migration over long geological timescales or until radioactivity has decreased to natural radiation levels. This study summarises the main geological evidence and arguments for the containment-providing rock zone (CRZ), including the host rock Opalinus Clay, as effective geological barriers for Switzerland’s deep geological repository. The information and data are part of Nagra’s comprehensive safety case within the framework of the general licence application. The geological assessment basis contains an integrated multi-scale site characterisation, covering data from 3D-seismic investigations and nine deep boreholes from the latest exploration campaign. Highlights of the geological data include: 1) high-resolution 3D-seismic datasets that image the subsurface structure, including undisturbed structural domains, key stratigraphic horizons, and the geometry of faults; 2) a comprehensive field and laboratory dataset that demonstrates that the hydraulic conductivities of the Opalinus Clay and remaining CRZ units are extremely low, that solute transport is diffusion-dominated, and that key properties have high vertical and lateral continuity; 3) independent natural-tracer profiles that developed over millions of years and confirm slow, diffusion-dominated transport across the CRZ; 4) a laboratory-derived mechanistic understanding and field evidence of self-sealing processes in the Opalinus Clay that show that fracture transmissivities decrease relatively rapidly after mechanical perturbation; 5) a systematic abstraction approach that groups geological units with similar properties and provides a modelling framework for evaluating safety- and performance-relevant processes; and 6) broad-ranging evidence that demonstrates the long-term geological stability of the Opalinus Clay with respect to the expected tectonic, geomorphological and hydrological changes during glacial-interglacial cycles over the next one million years. The synthesis presented here demonstrates how the geological data and its abstraction provide a robust and internally consistent basis for the safety assessment supporting the Swiss general licence application.

This study investigates the influence of currents on the sedimentary dynamics and geological processes within the Laurasian Seaway during the Middle Jurassic in Northern Switzerland. Using seismic, core, and log data, we identify and characterize a previously undocumented coral reef bearing platform, termed the & laquo;Herrenwis Unit & raquo;, within the region's predominantly siliciclastic strata. Contrary to earlier interpretations that attributed sediment transport primarily to storm activity and thickness variations to tectonic activity, our findings reveal that marine currents were the dominant force shaping the sedimentary architecture and reef development in this area. Strong evidence for current activity is provided by several depositional features. First, an elongated, mounded body within the underlying silty claystone unit forms the foundation of the oval-shaped Herrenwis reefal platform. Second, during the growth of the platform a moat establishes along the platform, separating the platform from the mounded basinal sediment. Finally, moat and mounded drift geometries are observed in the overlying strata, indicating continuous current influence during the Late Jurassic. The pronounced presence of contourite drifts, and the distinct oval morphology of the reef, aligned with prevailing currents, underscore the significant influence of these currents on sediment deposition and reef ecology. The transition from aggradation to progradation within the reef and the presence of an iron-rich hardground at its top further highlight the role of shifting hydrodynamic conditions in the reef's eventual demise. This study offers new insights into the complex interplay between marine currents and sedimentary processes in the Jurassic epicontinental seas, challenging existing paradigms on coral reef formation in low-relief, current-dominated environments.

Throughout the Pleistocene, valley glaciers repeatedly advanced into the forelands of the European Alps. However, the corresponding geological record is highly fragmentary and the regional glaciation history, especially prior to the last glacial maximum, is still poorly documented. We explored the archives of the Lower Aare Valley in the confluence area of the Aare river with Reuss and Limmat, focusing on the overdeepened Gebenstorf-Stilli Trough. In four scientific boreholes, ∼350 m of drill cores were recovered, and complemented with investigations of outcrops and reflection seismics in the nearby glaciofluvial Habsburg-Rinikerfeld Palaeochannel. The integrative interpretation of these data provides new insights into the local landscape evolution: We identified two generations of glacial basin infill in the Gebenstorf-Stilli Trough that are overlain by glaciofluvial gravels, and two distinct glaciofluvial gravel bodies in the neighboring paleochannel. In this specific local setting, gravel petrographic compositions and their statistical analysis prove to be powerful tools to identify inputs from the confluent catchments, to aid in lithostratigraphic classification, and to interpret the depositional and landscape histories. We suggest that it is mainly the penultimate glaciation, characterized by three separate ice advances, that shaped the present-day study area, and whose deposits are preserved in the Middle Pleistocene archives.

The safety assessment of radioactive waste repositories requires scenarios and forecasts of the erosional, climatic, and tectonic future evolution. One of the major challenges in the assessment of long-term landscape evolution for safety is that the relevant processes, models and model parameters are subject to a range of significant uncertainties. Assessments should provide the full range of conceivable developments using the best available scientific knowledge. Here, we present an assessment framework for future erosion with a rigorous uncertainty management. The approach anticipates erosion from fluvial, hillslope, and glacial processes over a timescale of 105-106 years. Uncertainties are addressed in a hybrid way, using probabilistic methods in combination with a scenario approach, whereby the chosen scenarios cover a wide range of possibilities. A protocol was followed to derive model parameter uncertainties that respect individual estimates of experts. The entire process is accompanied by a sensitivity analysis. We used the workflow to assess erosion in Northern Switzerland over the next million years. The results serve as input to site a deep geological repository for nuclear waste in Switzerland and to demonstrate its long-term safety.

Grain size variability in fine-grained sediments is a critical factor influencing the physical, geomechanical, geochemical, and hydrological properties of sedimentary rocks. Even small changes in grain size can significantly alter rock behavior. Despite many decades of research on fine-grained sediments in different depositional settings, studies focusing on the comparative and quantitative calibrated analysis of grain size variations in finegrained Mesozoic sediments are scarce. This study provides the first integrative, quantitative, comparative, and comprehensive analysis of grain size variability in the detrital fraction of the Opalinus Clay from northern Switzerland (Stadel-2 core), which serves as the designated host rock for radioactive waste disposal. The analyses include 2D image analysis, X-ray micro-computed tomography, laser particle size analysis, and sieving/decantation analysis, alongside mineralogical (X-ray diffraction, XRD) and geochemical (X-ray fluorescence, XRF) analyses. Strong correlations between grain size and elemental ratios (Si/Al, Ti/Al, Zr/Al, Zr/Rb) suggest that these ratios can serve as effective proxies for grain size variations in the Opalinus Clay, primarily controlled by the presence of quartz and phyllosilicates. Results evidence the dominance of silt-sized particles in the Opalinus Clay. Distinct trends of grain size coarsening and fining are observed based on XRF-derived grain size proxies, providing the base for further studies on sediment transport processes, including sediment provenance, flow strength, and current dynamics associated with the Opalinus Clay. Results highlight the importance of calibrating grain size variations in fine-grained sediments before their application in the understanding of rock properties and sedimentary processes.

The He-4/U-Th dating method can be used to estimate the residence time of pore waters in low-permeable rocks and consolidated sediments, serving as a proxy for sediment deposition time. This residence time is inferred from the accumulation time of radiogenic He-4 measured in the pore water being produced by the local decay of U and Th in the sediment matrix. We applied the He-4/U-Th method to date the pore waters of unconsolidated sediments from a glacial overdeepening in the Swiss Plateau (northern Alpine Foreland), where prior studies suggested sediments older than Marine Isotope Stage (MIS) 6 (191-130 ka). We show that compact and fine-grained (glaci)lacustrine sediments provide low-permeability conditions that allow 4 He to accumulate in the pore water and be preserved in the pore space. The He-4/U-Th dating indicates that the sediments between 40 m and 140 mare 606 +/- 122 ka. The dated infill was deposited in a glacial overdeepening eroded by a foreland glaciation larger than that of the Last Glacial Maximum (LGM). The results reveal extensive foreland glaciations and intense glacial overdeepening erosion during the early part of the Chibanian (i.e., Middle Pleistocene). This work highlights the potential of the He-4/U-Th method for dating sediments in similarly favorable hydrogeological settings.

Fine-grained sediments, including clay mineral-rich sediments, are essential for radioactive waste storage due to their sealing properties and low permeability. The Opalinus Clay in Switzerland and Opalinuston-Formation in Germany, summarized as Opalinus Clay, plays a key role in this context. Despite its apparent homogeneity, its depositional history remains complex. This study examined 20 drill cores using sedimentary petrography, grain size analyses, and revised thickness data from 477 drill cores across Switzerland, Germany, and France. Three lithological facies associations (FA) were identified: FA-1 (clay mineral-rich dominated), FA-2 (silt dominated), and FA-3 (silt/clay mineral-rich dominated with mainly calcareous beds). The Opalinus Clay shows overall poor to very poor sorting but with a dominant well-sorted silt fraction. Paleo-current velocity calculations based on the sortable silt fraction indicate lower values in more clayey subfacies (25 cm/s) and higher values in silty subfacies (27-32 cm/s). Multiple coarsening-and fining-upward trends are identified indicating a fluctuating current environment. The Opalinus Clay reveals thickness variations with the thickest deposits located in the central part of the Opalinus Clay Basin and thinner deposits towards the margins. The combination of sedimentary facies, grain size analyses and thickness variations suggest that the succession represents a shallow-water contourite drift formed by dominant north-to-south flowing currents. Hydrodynamic conditions changed through time and space, with strengthening of the current system towards the top of the succession and stronger currents in the south (Switzerland) compared to the north (Germany). Continuous current dynamics resulted in predictable trends in facies evolution with relatively few small-scaled facies variations. This uniformity is essential for the effectiveness as a geological barrier and its suitability for radioactive waste disposal.

A complex picture of the Pleistocene glaciation history of northern Switzerland has been identified over the last three decades. To gain further insights into the long-term landscape evolution, numerical dating is required. In the absence of alternative dating techniques, luminescence dating is the key method for establishing chronological constraints of past glaciations. However, this is presented with complex challenges, especially in regard to the resetting of the luminescence signal prior to deposition, the components contributing to the signal as well as the signal intensity and stability. In this study, the luminescence properties of glacially sourced deposits from northern Switzerland are assessed using single aliquot (SA) and single grain (SG) measurements of feldspar (F) and quartz (Q). While no obvious connection between bleaching and distal or proximal deposition in relation to the proposed ice margin is observed, most samples seem to reveal a partially bleached signature in F SG De measurements. This appears to be masked in the respective F SA measurements even though only few grains emit luminescence signals. In addition, comparisons between fading corrected infrared stimulated luminescence (IR) and post-infrared infrared stimulated luminescence (pIR) De values appear to be unreliable indicators of bleaching, even though these signals bleach at different rates. Hence, it is recommended to conduct both IR and pIR investigations in combination with Q measurements on a SG level. The dating potential of the investigated deposits remains rather limited, yet, in the sedimentologic context the presented results reveal that several glacial advances occurred prior to the Last Interglacial in the study area.

Glacially overdeepened basins are a common landform of subglacial erosion. However, the controlling erosional-depositional processes and their age remain poorly understood on a global scale. Terminal overdeepenings near the former glacier margins are critical for the understanding of subglacial processes and their development over time. This study examines the geomorphology and sedimentology of buried terminal overdeepenings eroded below the Rhein Glacier and adjacent lobes in the distal northern foreland of the European Alps. The evolution of erosion and infilling in the overdeepened troughs over time is investigated using high-quality drill cores ( 1463 m of core in total) that were logged for lithofacies, petrophysical, geotechnical and compositional properties. The drill data is integrated with 2D-reflection seismics ( 41 km in total) and supplementary subsurface data. This extensive dataset reveals that the studied overdeepened basins include twelve typical facies associations (partially emplaced in characteristic sequences) and characteristic architectural elements. These categories serve as effective tools to reduce the high facies variability and facilitate easier comparison and correlation of the valley fill. Our analysis shows that the formation of terminal overdeepenings on soft sedimentary bedrock (Molasse) is the result of a combination of erosional processes. Subglacial water erosion and evacuation are the dominant processes and active during periods of glacier-bed decoupling and flushing. Direct subglacial erosion occurs during glacier-bed coupling and is documented by bedrock glacitectonites. The valley fill architecture shows that the studied overdeepenings typically undergo a multiphase evolution, with several phases of overdeepening erosion, deposition and partial re-erosion (or re-activation). The combined dataset (including geochronological data) suggests that the overdeepenings were eroded during many, if not all, extensive glaciations during the Middle-Late Pleistocene that reached the distal foreland. These are findings relevant for the large number of overdeepenings known from the Northern Alpine foreland and overdeepened features worldwide. They corroborate the importance of overdeepenings as archives for the paleoenvironmental change and landscape evolution during the Quaternary.

The Opalinus Clay, a silty to sandy claystone formation, Early to Middle Jurassic (Toarcian and Aalenian) in age, has been selected as the host rock for deep subsurface disposal of radioactive waste in Switzerland. Over the past thirty years, numerous geotechnical, mineralogical, and sedimentological studies have been conducted on the Opalinus Clay within the framework of the Nagra (National Cooperative for the Disposal of Radioactive Waste) deep drilling campaigns and the Mont Terri Project, an international research program dedicated to the study of claystone. The present study aims to unravel the variability of the lateral and vertical facies of the Opalinus Clay in central Northern Switzerland and to place this variability in a regional and basinal context. Analyses of new cores drilled in central Northern Switzerland, including petrographic, mineralogical (X-ray diffraction, multi-mineral interpretation), geochemical (X-ray fluorescence), statistical (non-metric multidimensional scaling analysis), and bedding dip and azimuth data, shed new light on the depositional facies and the spatial and temporal variability of the Opalinus Clay. Petrographic descriptions encompass nine new drill cores using a revised subfacies/facies classification scheme based on texture (colour, grain size, bedding) and composition (mineralogy). Particularly, one new subfacies (SF6) is described and interpreted as mass-wasting deposits. The drill cores are correlated laterally using specific marker horizons. This correlation is achieved by combining thorough facies investigations with lithostratigraphy, biostratigraphy, and chemostratigraphy. Six to seven small coarsening-upward cycles and two long-term coarsening-upward sequences can be interpreted as regressive trends. The observed trends are influenced by the interplay between sediment supply, eustatic sea level change, synsedimentary subsidence, but also the palaeogeographic configuration in an epicontinental sea, provenance and delivery of sediments, current dynamics and climate change. Finally, combined results show that the current dynamics in the Opalinus Clay has been underestimated until now and new depositional models, including the occurrence of drift deposits, are discussed.

Following the extinction event at the Triassic - Jurassic boundary and during the Pliensbachian - Toarcian events, coral reef builders were severely affected, and the number of reef domains during the early Middle Jurassic was at an all-time low. However, new and updated data seem to show that corals were more widespread than previously thought, particularly during the Bajocian (170-168 Ma), but biostratigraphic markers are lacking to constrain the precise timing of reef evolution of this interval. A recently discovered 40 m-thick carbonate unit in northern Switzerland, on the northern Tethys margin, documents this rapid growth. Two cores from this unit display a reef with a high number of specimen but a low coral diversity, dated as Bajocian, which likely grew at a considerable water depth (upper limit of the mesophotic zone or 20-30 m). Additionally, it developed on top of clay mineral-rich accumulation characterised by low relief. Twelve different coral genera were identified, with a strong predominance of Periseris, Isastrea, Thamnasteria and Dendraraea. In the absence of other biostratigraphic markers, palynomorphs were used to provide accurate dating, which shows that palynology is a powerful tool for dating reef deposits. The results show reef growth during the early Bajocian, in the Sauzei and Humphriesianum ammonite zones, based on the palynological data, yielding similar ages to other Bajocian reef localities in the Eastern Paris Basin in France and Luxembourg dated simultaneously. These results indicate that the Middle Jurassic and more specifically the last two ammonite zones of the early Bajocian were periods suitable for coral reef builders, and that global regrowth of coral reefs occurred more rapidly than expected. A new Bajocian reef distribution is presented, showing no reefs at latitudes below 15(degrees). This distribution pattern is probably due to the fact that water temperature was too elevated (> 25 C-degrees) towards the equator for corals, which prevented reef growth. This would tend to favour a scenario in which the global climate, in particular temperature, is a determining factor for coral reef growth.

In the Alpine region of Central Europe, terrestrial Early Pleistocene deposits with preserved faunal and botanical remains are rare. The predominantly gravelly Hohere Deckenschotter (HDS) deposits of northern Switzerland and adjoining south-western Germany are considered the oldest Quaternary sediments in the northern Alpine Foreland, linked with the first extensive Quaternary Alpine glaciations. This multidisciplinary study investigates the Hasli Formation (HF), a unique silty unit with well-preserved biological remains within an HDS sequence at the Irchel Plateau north of Z & uuml;rich, providing new climatic and environmental data for these exceptional deposits, as well as crucial information about their age. Systematic mapping of the HF, in addition to the underlying and covering gravel units, has been coupled with sedimentary logging and biostratigraphic analysis at several sites. The HF is present over an area c.4 by up to 1.4 km, and where studied is 1.6-6.2 m thick. The sediments and biological material are indicative of overbank deposits accumulating within the damp floodplain of a large meandering river. The recovered small mammal remains are from eight arvicolid species or genera, including Mimomys pliocaenicus, M. reidi/tigliensis and Clethrionomys cf. kretzoii, which became extinct c.1.8 Ma, and Pliomys episcopalis/ simplicior, which first appeared c.2 Ma ago. The over 75k identified molluscs, include c.72k coming from 89 terrestrial species and over 3k from 28 aquatic taxa. The molluscan faunas from all locations where the HF has been studied share important biostratigraphic marker species, and indicate analogous climatic and environmental conditions. The marker species include several that became extinct during the Early Pleistocene, of which Clausilia stranzendorfensis and Cochlostoma salomoni, present throughout the HF, are the most important as they disappeared c.1.8 Ma. Many marker species have modern or palaeo-distributions that lie far to the west, south and east of the Swiss Plateau, showing that the climate was much warmer than today, typical for the Tiglian warm stage. The alluvial floodplain was covered by rather dense, mature woodland. Amino acid (AA) analysis shows that molluscan remains from the HF are among the oldest of the Quaternary shell material studied from across the Swiss Plateau. Palaeomagnetic data shows a change from reversed to normal polarity within the upper part of the HF. When combined, the small mammal and molluscan remains, palaeomagnetic measurements, AA geochronology and sedimentary data, suggest an age of 2.1-1.8 Ma for the HF. Recently produced cosmogenic dates bracket the age of the HDS gravels beneath the HF to depositional periods between 2.6 and 0.9 Ma, with the youngest ages being in disagreement with our findings. The abundance and diversity of the molluscs from the Irchel Plateau, with several rare extinct species, together with a notable small mammal assemblage, make this a key palaeontological site and an important reference point for European Quaternary biostratigraphy.

The Opalinus Clay (OPA), a claystone to silty claystone formation deposited during the latest Toarcian to mainly Early Aalenian, has been selected as the host rock for the disposal of radioactive waste in Switzerland. To establish which of the proposed repository sites is the best, Nagra (National Cooperative for the Disposal of Radioactive Waste) has drilled nine additional deep boreholes in Northern Switzerland, covering the complete Lower to Middle Jurassic successions. The present study compares these new boreholes with five existing drill cores, covering a distance of around 50 km. This extensive underground recovery allows a detailed and unique investigation of the Early to Middle Jurassic period. To establish a high-resolution chronology in the Jurassic successions, we combined carbon-isotope chemostratigraphy with ammonite and palynomorph biostratigraphy, as well as detailed lithological correlation of individual calcareous beds. The metre-step sampling for C-isotope chemostratigraphy for both carbonates and organic matter provides sufficiently distinct negative and positive trends to establish a high-resolution correlation between the drill cores. The geochemical data also support the lateral correlation of six calcareous beds or horizons within the OPA, identified as Bed-I to Bed-VI. The high-resolution C-isotope data can be correlated with existing data from Northern Switzerland, Southern Germany (e.g. Dotternhausen), France (e.g. Le Brusquet), and other European successions. The major perturbation in the carbon cycle observed in the Toarcian Rietheim Member confirms previous findings of the negative C-isotope excursion (CIE), which can be linked with the Toarcian Oceanic Anoxic Event (T-OAE). Additionally, a newly identified negative CIE (Opalinum nCIE) in the lower Opalinum Subzone of the Opalinum ammonite Zone can be correlated across all Nagra boreholes in Northern Switzerland. This nCIE follows almost the horizon with the calcareous concretions located approximately 10 m above the base of the OPA (Bed-I). In the uppermost Opalinus Clay, a positive CIE (Bifidatum pCIE) was documented within Bed-VI, which can be tied by ammonites and palynomorphs to the Bifidatum Subzone of the Opalinum Zone. Bed-VI can be interpreted as a sequence boundary possibly related to global sea-level variations. The integration of the C-isotope chemostratigraphy, biostratigraphic data, and lithological observations enables the establishment of a detailed chronostratigraphic framework.

Here we develop an amino acid chronology to help establish a dated sequence for the important Early Pleistocene Höhere and Tiefere Deckenschotter lithostratigraphic units, as well as other Quaternary deposits from the Swiss Plateau. Age discrimination is possible between the Quaternary sites from the Swiss Plateau in six different biominerals: Bithynia opercula, shell fragments from Fruticola, Arianta and Cepaea, slug plates and worm granules. This chronology is compared with new and existing dating information derived from palaeomagnetic data, pollen, lithostratigraphy and numerical dating methods (such as optically stimulated luminescence; OSL), as well as biostratigraphic data derived from a study of Early to Late Pleistocene molluscan faunas from the Swiss Plateau. In general, the stratigraphy has been validated, with some new chronological insights at some of the few sites.

The Deckenschotter is a fluvial to glaciofluvial gravel unit in northern Switzerland and southern Germany. The deposits are considered the oldest preserved glacial to interglacial Quaternary deposits in the northern Alpine foreland and are thus important geomorphological markers for landscape evolution. Nevertheless, the age of the deposits is only approximately known and subject to controversial debates. This study presents the results of an extensive palaeomagnetic investigation carried out on intercalated fine-grained sediments at 11 sites of the Höhere Deckenschotter (HDS) and at 5 sites of the Tiefere Deckenschotter (TDS). The HDS show reversed and normal magnetisations, indicating deposition > 0.773 Ma, while the TDS exhibit only normal directions. Age constraints for the different sites are discussed in the light of evidence from other studies. The study therefore clearly supports the efforts to determine the age of the Deckenschotter. As data from previous palaeomagnetic studies on the HDS and TDS have not been published or preserved, this is in fact the only data-based palaeomagnetic study available.

In northern Switzerland, Middle Muschelkalk evaporites (Zeglingen Formation) were deposited under arid conditions in the southernmost part of the epicontinental Central European Basin during times of reduced inflow of sea water from the Tethyan realm. Because of their marginal position in the basin, direct and detailed correlation of Muschelkalk sediments of northern Switzerland with equivalent strata in interior parts of the basin is not straightforward. Based on detailed sedimentological logging of 640 m of drill cores from ten wells in northern Switzerland, 22 lithofacies and 10 lithofacies associations were distinguished for the Middle Muschelkalk evaporites. High-resolution regional correlations of gamma-ray logs record substantial thickness variation of the evaporites. Locally, dissolution was recognized by visual core examination that could be dated to Middle Triassic times and that was likely related to subsurface fluid flow along deeper seated faults. In combination with the regional thickness variation, the dissolution phenomena suggest a tectonically active depositional setting in the Middle Triassic. Middle Muschelkalk evaporites consist of nine types of mainly auto-cyclic shallowing- or brining-upward mini-cycles which form a correlatable succession of five distinct 4th order cycle-sets. Despite the tectonically active depositional environment, most lithofacies encountered appear to have nearly flat bounding surfaces. Thus, marine transgressions flooded wide areas nearly simultaneously. The corresponding deposits serve as reference levels to tie the peripheral facies of northern Switzerland into the supra-regional context.

While timing and ice extent of the last glacial maximum are generally well known, the courses of earlier glaciations have remained poorly constrained, with one of the main reasons being the scarcity of sedimentary archives. This study introduces a new palaeolake record from a Mid-Pleistocene glaciofluvial channel system in the Lower Aare Valley (Northern Switzerland). The record of Rinikerfeld comprises a >40 m long succession of Quaternary deposits that are targeted by multi-method sedimentological analysis. Sedimentary facies together with geochemical and geotechnical parameters, pollen content, as well as luminescence ages allow the reconstruction of the establishment, evolution and infilling of the early Marine Isotope Stage 6-aged Rinikerfeld Palaeolake. A drastic change in lake sediment composition and structure indicates cessation of the initial glacially derived input, which is explained by landscape modification and drainage rerouting during the Penultimate (Beringen) Glaciation. Geochemical and palynological data further reveal cold, initially periglacial but slightly ameliorating, climate conditions, while the lake was progressively filled up by local runoff, before being buried by periglacial colluvial diamicts, and potentially overridden by ice. It is therefore concluded that the onset of the Beringen Glaciation was an environmentally as well as geomorphically dynamic time period in the Northern Alpine Foreland.

The morphology of glaciofluvial terrace staircases is controlled by the interactions of fluvio- and geodynamic factors. Prerequisites for their formation are periodically aggradating rivers (e.g. associated with Quaternary cold periods), in combination with tectonic uplift (e.g. Bridgland & Westaway, 2008). Glaciation can thereby remarkably pronounce this effect where the end of a glacial cycle is typically associated with immediate incision. Abandoned plains represent then a morphologic snapshot, covering a very short period of time. Consequently, they can be highly suitable to act as a morphostratigraphic marker for climatic and geodynamic processes. Especially in this context, regional scale systematic analyses appear very promising and have so far not been subject to intense research. We present a GIS-based morphostratigraphic method and toolset, using the R programming environment. The toolset can be used to project the full elevation information of a high-resolution digital elevation model (DEM) of a river channel (incl. full valley flanks and/or unconfined outwash plains), to 2D (paleo-) river long-profiles, together with other geodata, if available (e.g. existing terrace maps and outcrop information). DEM data is displayed semitransparently in the profile view, making terrace-tops stand out as more or less dark and flat lines. This allows plausibility/quality analysis of existing maps, as well as mapping procedures. Furthermore, on the basis of the projected data, DEM pixels of corelated terraces can be statistically evaluated and models (regression functions) fitted, which allows the reconstruction and measurement of parameters of paleo-riverbeds (e.g. relative height above local base-level, local slope, concavity). We applied this method in the North Alpine Foreland to an extensive terraced landscape, representing a large age span until up to Early Pleistocene age, as well as abundant data on terrace stratigraphy (i.e. from geological mapping, drilling campaigns and relative and absolute age constrains), including high resolution digital elevation models. Despite the long history of Quaternary research in the region, a consistent stratigraphic model of the Quaternary period is currently missing. In fact, the last mountain range scale model was proposed more than 110 years ago by Penck and Brückner (1909). Local findings by geologic surveys (Switzerland, Germany and Austria) unveil strong inconsistencies and an updated model is highly needed. Based on a new code in the R programming environment we evaluate existing stratigraphic models and show how glacio- and geodynamic implications can be statistically derived from terrace hypsometry. References: Bridgland, D., Westaway, R. (2008): Climatically controlled river terrace staircases: A worldwide Quaternary phenomenon. Geomorphology 98, S.285-315. Elsevier. doi:10.1016/j.geomorph.2006.12.032 Penck, A., & Brückner, E. (1909): Die Alpen im Eiszeitalter. Leipzig: Tauchnitz.

Fluvial and glaciofluvial sediments in the Northern Alpine Foreland record detailed history of the Quaternary glaciations and climatic changes. These sediments and associated landscapes have been typically classified using the Penck and Brückner’s concept for four terrace levels; the so-called Niederterrasse, Hochterrasse, Tiefere Deckenschotter and Höhere Deckenschotter. Sediments of Niederterrasse and Hochterrasse were dated using quartz and feldspar luminescence dating, however, older sediments (Tiefere and Höhere Deckenschotter) are beyond the upper limit of the method and are difficult to date. In this study we tested the feasibility of quartz electron spin resonance (ESR) dating using the Ti centre for sediments from northern Switzerland.Eight samples were used in this work; these are two modern river sands from a bank (GRUE1) and a sand bar (GRUE0) of the River Thur at Grüt, fluvial-lacustrine (BER6) and fluvial-fluviglacial (BER3) sediments from Beringen, which have OSL dates of ~25 and ~150 ka, Tiefere Deckenschotter from Hungerbol (HUNE2), and Höhere Deckenschotter from Irchel Hasli (HASE1, HASE2) and from Irchel Steig (STEE2). Quartz ESR dating was conducted using the single aliquot regenerative dose protocol using three aliquots each for the Ti-Li and Ti-H centres. Dose recovery tests were also performed using two young samples (GRUE1 and BER6) by adding ~1000 Gy on top of the natural aliquots. Dose recovery ratios were satisfactory for both samples and for both Ti-Li and Ti-H centres. The apparent ages of samples from Tiefere and Höhere Deckenschotter are in stratigraphic order, ranging from 530 to 890 ka for the Ti-Li centre. However, the residual dose obtained from modern and young samples were significant, with a mean of ~750 Gy for the Ti-Li centre and ~200 Gy for the Ti-H centre. These residual doses are corresponding to ~70 % and ~40 % of the natural equivalent dose of the Deckenschotter samples, which makes the evaluation of actual burial dose very difficult. Ages corrected for the residual dose obtained from modern and young samples result in unreasonably young ages between ~150 and ~320 ka.

The Opalinus Clay, an argillaceous to silty claystone formation, is known in Switzerland as being the selected host rock for deep geological disposal of high-, intermediate- and low-level radioactive waste. Since the 1990s, various properties of the Opalinus Clay have been studied within the framework of the Nagra (National Cooperative for the Disposal of Radioactive Waste) deep drilling campaigns and the Mont Terri Project (international research program dedicated to the investigation of claystone). The Opalinus Clay succession was deposited during the Late Toarcian to Early Aalenian in an epicontinental sea covering central Europe. Although the Opalinus Clay is relatively homogeneous at formation-scale compared to other Mesozoic formations in northern Switzerland, significant lithological variations occur at lower scales. Besides m-scale lithofacies variations, high, intra-facies lithological variability occur at dm- to cm-scale. The facies diversity is primary attributed to regional differences in depositional, environmental and diagenetic conditions. In order to harmonize petrographic descriptions in an objective and quantitative way within all fields of research related to the Opalinus Clay, a subfacies classification scheme has been developed (SF1 to SF5, applied mostly on Mont Terri drill cores). The subfacies are distinguished by parameters such as texture (grain size, bedding, fabric and colour) and composition (nature and mineralogy of components). The five subfacies types can be further refined by additional attributes and sedimentary characteristics (biogenic, diagenetic, structural). Subfacies descriptions are crucial to understand the lateral and vertical facies variability at regional scale. Moreover, accurate petrographic descriptions are a crucial prerequisite to many geotechnical studies and the prediction of petrophysical properties. The main goal of the present study is to define a subfacies classification model covering the entire Opalinus Clay succession of the Mont Terri rock laboratory and successions deposited further to the east. Nagra is currently investigating three potential sites for radioactive waste storage within the Opalinus Clay in northern Switzerland. Nine new drill cores are used to apply the subfacies classification scheme. If necessary, the subfacies classification scheme will be adapted considering regional facies heterogeneities. Based on the new subfacies classification, depositional models for the Opalinus Clay will be refined.