The Tibetan Plateau (TP), often referred to as the “Third Pole” and “Asian Water Tower”, serves about two billion people downstream with its water resources; thus, investigations of past climate changes on the TP have significant socio-economic implications for both the scientific community and governmental concerns. Numerous lakes on the plateau provide valuable archives to carry out paleoenvironmental change studies on different time scales by drilling sediment cores. With the support of the ICDP (NamCore project, Expedition 5073) and other funding, we accomplished a drilling campaign in a high-altitude, deep lake (Nam Co, 4718 m) on the Tibetan Plateau in the summer of 2024. In total, ~950 m of cores was recovered from seven holes at one site, with a deepest drilling depth of 510 m b.l.f., making NamCore a great success among ICDP lake drilling projects in the past several decades with respect to its altitude and maximum penetration depth. These achievements enable us to study past climate changes in this area potentially back to ~1 Ma and their linkages with other regions globally. Three core opening and sampling parties of the NamCore project have been organized in Beijing, where the cores were stored, to complete the splitting of all cores. Core descriptions, magnetic susceptibility scanning of the entire sequence combined with other analyses (e.g., grain size, organic/inorganic carbon content, biomarkers and pollen, etc.) on core catcher samples have revealed sediment variations, which can distinctly show the fluctuations between glacial and interglacial cycles, although the chronology using various approaches is still challenging. The results show four major lithologies throughout the drilled cores including calcareous mud, non-calcareous mud, sand and calcareous mud with ferric staining. Calcareous mud dominates the upper ~120 m and ferric-stained mud mainly appear in the sections deeper than ~320 m. Many sand layers with different thickness occur in the entire sequence but mostly in the middle part. Nothing has been retrieved in a section greater than 30 m in thickness in the lower part, which probably indicates a remarkable change in the sedimentary environment associated with a glacial period. Time series analysis on the magnetic susceptibility data shows two prominent cycles at 10.1 m and 21.4 m, which potentially correspond to the orbital precession and obliquity forcing of 21 ka and 41 ka, respectively. This cyclostratigraphic approach will be helpful to constrain the chronology and, by comparison with stalagmites in monsoonal areas and ice cores in polar regions, plays an important role in discovering the different drivers of climate change from low and high latitudes. However, more efforts are still needed to obtain absolute ages to establish a precise timeframe for these cores.

How to cite: Wang, J., Adolph, M.-L., Cidan, Z., Zhu, L., Haberzettl, T., Vogel, H., Clarke, L., Henderson, A., Spiess, V., Ju, J., Ma, Q., Kou, Q., and Daut, G.: Scientific Drilling on the Third Pole: achievements of the highest ICDP lake drilling project on the Tibetan Plateau (Nam Co, 4718 m.a.s.l), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7514, https://doi.org/10.5194/egusphere-egu26-7514, 2026.

Ostracods from sediment cores of the ICDP NamCore drilling project were analysed to document their distribution, abundance, and preservation, and to explore their potential for reconstructing past lacustrine conditions on the central Tibetan Plateau. Selected core catcher samples covering sediment depths from ~8 to 470 m were investigated for their microfossil content. Sediment samples (10–15 g each) were wet-sieved at 63 µm and 200 µm, and the >200 µm fraction was examined under a stereomicroscope. Ostracods were assessed semi-quantitatively and assigned to five abundance categories (absent, 1-10, >10, >100, >1000 valves per sample). Preservation states were evaluated qualitatively, and taxonomic identifications were based on established regional faunal keys.

Ostracods represent the only fossils observed in the sand-sized fraction of the analysed samples. Their abundance varies strongly, ranging from complete absence to more than 1000 valves per sample, with approximately half of the samples containing more than 100 valves. Preservation is generally good, although weakly etched, fragmented, compacted, or deformed valves occur, particularly below ~180 m core depth. Assemblages are of low diversity, with a maximum of five species per sample. At least six ostracod taxa were identified, including Leucocytherella sinensis, ?Leucocythere dorsotuberosa, ?Leucocythere postilirata, Ilyocypris ?bradyi, a smooth Ilyocypris species of uncertain taxonomic status, and juvenile Candona spp. The taxonomic assignment of ?Leucocythere dorsotuberosa and the smooth Ilyocypris species is the subject of ongoing investigations.

Variations in ostracod abundance, species level assemblage composition, and variable preservation suggest changes in depositional and post-depositional conditions through the core. While the presence of ostracods throughout most sections is consistent with predominantly lacustrine settings, intervals with low abundances or poor preservation may reflect a range of factors, including lake-level changes, sedimentation dynamics, or taphonomic overprinting. Further quantitative analyses, improved taxonomic resolution, and integration with independent proxies are required to refine palaeoenvironmental interpretations.

How to cite: Schmitz, O., Frenzel, P., Pint, A., Adolph, M.-L., Clarke, L., Henderson, A., Vogel, H., Wang, J., Zhu, L., Höhle, M., Wrozyna, C., and Haberzettl, T.: Ostracods from sediment cores of the ICDP NamCore drilling project provide insights into long-term lacustrine evolution on the Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13464, https://doi.org/10.5194/egusphere-egu26-13464, 2026.

A central objective of the NamCore ICDP project is to understand Quaternary biotic dynamics—specifically species diversity, distribution, and evolution—in relation to Asian monsoon variability and orbitally driven climate change. Lacustrine ostracodes are therefore ideal indicators to assess (1) whether Nam Co served as a glacial refugium for cold-adapted species during glacial periods, (2) how biota responded to glacial–interglacial environmental transitions, and (3) whether the lake exhibits a high ecological resilience to environmental change.

To address these objectives, a multi-scale analytical approach was applied. Ostracode valve analyses were conducted on 43 core catcher samples spanning depths from 8 m to 470 m b.l.f., corresponding to a stratigraphic resolution represented by intervals of 3–35 m, to provide an overview of broad-scale changes in ostracode distribution and abundance. To obtain higher-resolution data on species distribution and morphological variability, additional samples from core sections within the upper 33 m b.l.f. were analyzed at 16 cm intervals. Morphometric analyses of valve outline shape and size are intended to identify either gradual or abrupt changes in morphological variability. Environmentally driven morphological responses are expected to manifest as gradual shifts in size and/or shape, whereas re-colonization from other lakes may produce distinct morphological signatures, resulting in discontinuous variation in size or shape.

Preliminary results indicate that ostracode abundance and species composition are highly variable, with ostracodes absent below 470 m b.l.f. In total, ten species were identified, with a maximum of five species per sample. Generally, samples from the uppermost 30 m contain four species that are absent in the lower sections of the record. Although Leucocytherella sinensis and ?Leucocythere dorsotuberosa represent the most abundant taxa, no species occurs continuously throughout the sedimentary record.

Detailed analyses of species composition, combined with morphometric investigations, are expected to elucidate whether the discontinuous ostracode distribution pattern reflects repeated lake colonization events associated with, e.g. glacial–interglacial cycles. Such findings would have significant implications for understanding the role of the Tibetan Plateau as a biodiversity refugium during Quaternary climate oscillations and for reconstructing paleoenvironmental conditions from ostracode assemblages in high-altitude lake systems.

How to cite: Wrozyna, C., Hoehle, M., Adolph, M.-L., Frenzel, P., Schmitz, O., Clarke, L., Henderson, A. G., Vogel, H., Wang, J., Zhu, L., and Haberzettl, T.: Lacustrine ostracodes from Nam Co (Tibetan Plateau) indicate biotic responses to Quaternary climate change (NamCore ICDP project), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5230, https://doi.org/10.5194/egusphere-egu26-5230, 2026.

The mineral abundance, their properties and geometrical arrangement on small spatial scales directly affect the physical characteristics of the continental crust at large scales. Consequently, the mineral assemblages determine to a large extent how geophysical methods respond to these rocks. Determining the mineral volume fractions is an essential first step for modelling and interpreting geophysical data, constraining crustal structure, and understanding the evolution of the Earth’s lithosphere. In this study, we develop a Bayesian inversion framework that integrates petrophysical information from downhole well logs and multi-sensor core logging data with X-ray fluorescence (XRF) data to estimate continuous mineral fraction profiles along two ICDP-DIVE boreholes (Greenwood et al. 2026) drilled through the exhumed lower continental crust of the Ivrea–Verbano Zone (IVZ) with almost 100% core recovery. The framework involves two schemes: (1) an overdetermined inversion of relative sparse XRF oxide weight fraction data from powdered rock samples combined with core density logs, and (2) a severely underdetermined inversion of potassium, magnetic susceptibility, and core density logs, conducted by groups derived from a cluster analysis of these logs. The latter scheme is constrained by the first scheme, which allows to retrieve a continuous mineral fraction estimates along both boreholes from the limited number of 3 petrophysical logs. An ensemble Markov Chain Monte Carlo algorithm (Cheng et al. 2022) is adapted to recover the posterior mineral fraction distributions while quantifying uncertainties. An essential input is the prior knowledge of the minerals present and their chemical formula, which may require supplementary measurements, especially for minerals such as amphibole, whose chemical formula is difficult to determine. The results show that the XRF Oxide–density inversion approach provides robust mineralogical estimates that are consistent with independently obtained modal estimates from section observations. The constrained inversion of the petrophysical logging data successfully captures mineral fractions across most lithologies despite the underdetermined nature of the problem. The study demonstrates that combining XRF-derived oxide fractions with continuous downhole and core logging data within a Bayesian framework provides a powerful approach for obtaining quantitative, mineral fractions in a range of lower crustal lithologies.

Cheng, L., Jin, G., Michelena, R., & Tura, A. (2022). Practical Bayesian Inversions for Rock Composition and Petrophysical Endpoints in Multimineral Analysis. SPE Reservoir Evaluation & Engineering, 25(04), 849–865. https://doi.org/10.2118/210576-PA

Greenwood, A., Venier, M., Hetényi, G., Ziberna, L., Heeschen, K., Pacchiega, L., Lemke, K., Dutoit, H., Bonazzi, M., Degen, S., Li, J., Secrétan, A., Trabi, B., Tholen, S., Lefeuvre, N., Auclair, S., Mariani, D., Del Rio, M., Černok, A., Bhattacharyya, A., Narduzzi, F., Mansouri, H., Urueña, C., Beltrame, M., Hawemann, F., Velicogna, M., Toy, V., Dominique, J., Longo, A., Tonietti, L., Barosa, B., Brusca, J., Nappi, N., Gallo, G., Esposito, M., Diana, S. C., Bastianoni, A., Eckert, E. M., Confal, J. M., Pondrelli, S., Piana Agostinetti, N., Tertyshnikov, K., Caspari, E., Truche, L., Wiersberg, T., Baron, L., Giovannelli, D., Pistone, M., Zanetti, A., Müntener, O. (2025): Drilling the Ivrea-Verbano zonE: DIVE 1 – ICDP Operational Report, Potsdam: GFZ Data Services, 109 p. doi:10.48440/ICDP.5071.001

How to cite: Li, J., Secrétan, A., Degen, S., Caspari, E., Greenwood, A., Venier, M., Lemke, K., Ziberna, L., Hetényi, G., and Müntener, O.: Integrating Petrophysical Logging and XRF Data for Mineral Fraction Estimation of Lower Crustal Rocks from the ICDP-DIVE Project using a Bayesian Inversion Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11216, https://doi.org/10.5194/egusphere-egu26-11216, 2026.

As part of a multidisciplinary effort to characterize the deep continental crust, two scientific boreholes were drilled in the Ivrea Verbano Zone (IVZ, Western Alps, Italy), one of the few near-complete continental crustal sections exposed on Earth's surface (Pistone et al. 2020). The boreholes were drilled within the Drilling the Ivrea Verbano ZonE (DIVE) project, supported by the International Continental Scientific Drilling Program (ICDP-5071; Li et al. 2024; https://gfzpublic.gfz.de/pubman/item/item_5037328) . Among various well log measurements, time-domain induced polarization (TDIP) logs with two electrode spacings (16″ and 64″) were collected in both wells, from which chargeability data is inferred. The boreholes intersect a wide range of lithologies hosting sulfides and oxides, either disseminated or concentrated along veins and fractures, which represent potential sources of chargeability. A set of eleven samples from these boreholes were analyzed using both scanning electron microscopy (SEM) and micro-computed tomography (μCT). The following mineralogical and microstructural characteristics have been evaluated so far: the type and abundance of metallic minerals (expressed as volume and area fractions); the perimeter-to-area and surface-to-volume ratios and the preferred orientation of these conductive phases. These parameters were compared to the TDIP response signal at the corresponding depths of the borehole, resulting in the following findings:

i) Borehole chargeability is not necessarily proportional to the abundance of metallic minerals;

ii) The total surface area (which is high for fine grain sizes) plays a dominant role over the total volume fraction of metallic minerals;

iii) The shape preferred orientation of conductive phases appears to be a key factor influencing the measured chargeability;

iv) The presence of other mineral phases, such as graphite, may mask or amplify the response of metallic minerals depending on their structural relationship.

While no deterministic relationship has been identified at this stage, this work outlines a potential path to improve the interpretation of TDIP data in mineralized systems and to define complementary yet efficient tools for assessing the economic potential of mineral deposits.

References

Li, J., E. Caspari, A. Greenwood, et al. 2024. “Integrated Rock Mass Characterization of the Lower Continental Crust Along the ICDP‐DIVE 5071_1_B Borehole in the Ivrea‐Verbano Zone.” Geochemistry, Geophysics, Geosystems 25 (12): e2024GC011707. https://doi.org/10.1029/2024GC011707.

Pistone, Mattia, Luca Ziberna, György Hetényi, Matteo Scarponi, Alberto Zanetti, and Othmar Müntener. 2020. “Joint Geophysical‐Petrological Modeling on the Ivrea Geophysical Body Beneath Valsesia, Italy: Constraints on the Continental Lower Crust.” Geochemistry, Geophysics, Geosystems 21 (12): e2020GC009397. https://doi.org/10.1029/2020GC009397.

How to cite: Ventola, I., Caspari, E., Greenwood, A., Hawemann, F., Venier, M., and Virginia, T.: Investigating Borehole TDIP Response in the Ivrea-Verbano Zone (ICDP-DIVE project):Linking Chargeability to Mineral Distribution from SEM and MicroCT Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20662, https://doi.org/10.5194/egusphere-egu26-20662, 2026.

The mobility of sulphur and chalcophile metals through the lithosphere remains poorly constrained, yet it is likely to have a significant impact on metal budgets and the localisation of ore systems that underpin the supply strategic commodities for the energy transition.

Increasing evidence suggests that sulphur and chalcophile metals can be redistributed via multiple, potentially overlapping processes, including sulphide melt migration, fluid-mediated transport, partial melting, and deformation-assisted remobilisation. These mechanisms operate across a wide range of pressure-temperature conditions and may decouple metal transport from large-volume magmatic fluxes, producing complex metal redistribution patterns within the lithosphere.

In this framework, deep mafic-ultramafic cumulates in lower crustal zones act as major reservoirs and transfer hubs where sulphide melts can sequester a large fraction of the metal budget, while being episodically mobilised within melt-bearing cumulate frameworks, enabling upward transfer to upper‑crustal levels (i.e Holwell et al. 2022). A complementary mechanism for enriching and moving sulphur and copper is provided by devolatilization and wall-rock assimilation. Fluids can already effectively mobilise sulphur and copper under subsolidus conditions, enhancing mobilisation that may have already accompanied partial melting and produce Cu-rich sulphide droplets that can attach to fluid bubbles (i.e Blanks et al. 2020) or carbonate melt droplets (i.e Cherdantseva et al. 2024) which can be transported buoyantly within silicate melt (i.e Virtanen et al. 2021). Deformation potentially introduces an additional mechanism of redistribution, which is highly relevant for interpreting sulphide signatures in deep crustal rocks, and metamorphism commonly overprints ore systems, creating favourable conditions for further mobilization of critical metals (i.e Cugerone and Cenki 2025).

Newly acquired continuous drill core from the Ivrea-Verbano Zone provides an exceptional opportunity to investigate these processes in a well-constrained lower-crustal setting. The core samples mafic and ultramafic lithologies across documented igneous, metamorphic, and structural domains, allowing sulphide occurrence, texture, and chemistry to be examined in their primary context, while also distinguishing deep-crustal magmatic processes from later deformation- or fluid-assisted remobilisation.

Borehole 5071_1_A is dominated by gabbroic lithologies, with intercalations of granulite-facies metasediments and pyroxenites, as well as intrusive gabbronorites. We combine (i) XRF elemental mapping on the flat split core surfaces to track core-scale variations and identify sulphide-rich intervals and their structural/lithological controls, with (ii) SEM-EDS analyses to characterise sulphide mineralogy and (iii) LA-ICP-MS trace-element analyses of the major sulphide phases to constrain phase-dependent trace-element budgets and variations among various host lithologies as well as different textures. The sulphide assemblage is dominated by Fe-Ni-Cu sulphides (pyrrhotite-pentlandite-chalcopyrite), occurring both as disseminated interstitial grains and as foliation- and fracture-related networks associated with localised deformation and late-stage fluid pathways. Across these textural populations, trace-element systematics display different variations consistent with sulphide-silicate equilibration as well as later stage remobilisation.

By linking centimetre-scale elemental maps from continuous core to micro-analytical sulphide fingerprints, the ICDP-DIVE record allows us to advance the exploration and resource assessment for critical raw materials in complex crustal systems.

How to cite: Venier, M., Caruso, S., Fiorentini, M., Müntener, O., Ziberna, L., and Toy, V. and the DIVE Science Team: Lower continental crust sulphides from the Ivrea-Verbano Zone (ICDP-DIVE project 5071): textures, trace-element chemistry and mobility, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22443, https://doi.org/10.5194/egusphere-egu26-22443, 2026.

How can rocks obtained by scientific drilling increase our understanding of deformation, stress, and strength in one of Earth’s classic collisional orogenic belts? By integrating scientific drilling data with high-resolution laboratory measurements, this study presents a combined structural, mineralogical and geomechanical characterization of the Scandinavian Caledonides, based on data from the COSC-2 borehole acquired during the ICDP logging campaign in 2022 . From the surface to approximately 1200 m depth, the borehole intersected an extensive Early Phanerozoic sedimentary succession, dominated primarily by wacke, shale and siltstone. Beneath this succession, extending to 2276 m, lies a crystalline basement comprising a volcanic sequence, including porphyry, gabbro and gabbroid rocks, intruded by dolerite dykes. The contact between the sedimentary succession and the crystalline basement is relatively undisturbed, with a thin regolith covering the altered top of the porphyry.

A key objective of our study is to investigate the physical properties and in-situ stress state of the COSC-2 rocks using laboratory tests on selected core samples. Specifically, we examine how stress magnitudes vary with depth, which stress regime dominates the area, how rock stiffness varies with lithology, mineralogy, and depth, and whether laboratory-derived elastic properties are consistent with downhole sonic log measurements (Vp and Vs). To address these questions, a suite of laboratory measurements was conducted on 19 core samples, including Brazilian tensile strength (BTS), uniaxial compressive strength (UCS), P- and S-wave velocities, Poisson’s ratio, Young’s, bulk, and shear moduli, grain and bulk density, and quantitative mineralogical analyses using X-ray diffraction (XRD) and electron microprobe analysis (EPMA). Our findings show that crystalline rocks exhibit in general a higher stiffness and compactness, reflected in elevated wave velocities and elastic moduli, combined with greater densities and lower porosity resulting in greater mechanical strength, both in compression and tension loading. This behaviour is reflected in specific samples, which record some of the highest BTS and UCS values. In contrast, three samples in doleritic and gabbroic rocks display unexpectedly low BTS values (19–20 MPa) and UCS values (180–211 MPa) compared to the other crystalline basement samples. Analysing the mineralogical composition, we found the presence of primary and secondary phyllosilicates in these rocks, which likely weaken the rock fabric and can be responsible for the reduced strength. In contrast, the overlying sedimentary rocks exhibit lower stiffness and strength but greater variability largely controlled by porosity and internal heterogeneity.

Of course, such geomechanical properties are also controlled by the presence of microcracks, open and cemented veins, mineral alignment and the precipitation of secondary minerals reflecting enhanced fluid flow and fluid-rock interaction processes. Especially the occurrence of secondary mineral phases identified through XRD and EMPA further reveal a complex tectono-metamorphic history. Together, these findings provide a solid framework for geomechanical modelling and advance our understanding of the evolution of collisional orogens.

How to cite: Pierdominici, S., Lopera Restrepo, A. P., Kottkamp, W., Schleicher, A. M., Wilke, F. D. H., and Schmitt, D. R.: The influence of geomechanical properties on rock strength in the ICDP COSC-2 borehole, at Are, Sweden, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5610, https://doi.org/10.5194/egusphere-egu26-5610, 2026.

The West Antarctic Ice Sheet (WAIS) is currently experiencing accelerated mass loss and contains enough ice to raise global sea levels by up to five meters if it were to melt completely. The objective of the international and interdisciplinary SWAIS2C project (Sensivity of the West Antarctic Ice Sheet to 2 Degrees Celsius of Warming) is to understand past and present factors influencing WAIS dynamics and to reconstruct WAIS response to warmer temperatures, including those exceeding the +2°C target outlined in the Paris Climate Agreement.

In its third season, the SWAIS2C project targeted the second drilling location Crary Ice Rise Site 1 (CIR), a grounded ice sheet upstream the Ross Ice Shelf. After hot water drilling through ~516 m of ice, rotary coring retrieved a sediment succession of 228 m length comprising different lithological units.

The LIAG Institute for Applied Geophysics and the German Helmholtz Centre for Geosciences (GFZ) are in charge of geophysical downhole logging operations and retrieved the first such dataset below grounded ice. The spectrum gamma radiation (SGR) tool records the natural radiation and its components – the K-, Th-, and U-concentration – of the surrounding sediments. The data indicate distinct boundaries between the main lithological units, but minor variations and ratios of the measured elements indicate smaller differences within the units. Particularly in transitions between major units, patterns in the data may reflect changing paleo-environmental conditions. This data set will be valuable for the ongoing project as it is an in-situ, continuous record of drilled sediment succession with high accuracy depth measurements.

We give a brief overview of the SWAIS2C project, focus on the downhole logging data measured as part of the project and relate the results to other data sets from below/around the Ross Ice Shelf.

How to cite: Ulfers, A., Horgan, H., Patterson, M., Dunbar, G., Kulhanek, D., Levy, R., van de Flierdt, T., Pierdominici, S., and Zeeden, C. and the SWAIS2C Science Team: Characteristics of spectrum gamma radiation (SGR) data from geophysical downhole logging in the SWAIS2C project – West Antarctica , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23159, https://doi.org/10.5194/egusphere-egu26-23159, 2026.

The Middle Miocene represents one of the warmest intervals in Earth’s recent geological history. Understanding the climate dynamics of this period can provide valuable insight into how the climate system may respond to future anthropogenic forcing. The study of tropical regions during the Miocene is particularly important, because these environments are underrepresented in climate records. Since the Miocene, Australia’s climate has undergone substantial changes driven by the northward drift of the continent, its collision with Southeast Asia, and the associated reorganisation of oceanic circulation around the Maritime Continent. Northern tropical Australia is presently influenced by a monsoonal system that forms part of the broader Asian Monsoon; however, the Australian Monsoon remains poorly understood, particularly with respect to its onset and variability. Investigating monsoon dynamics across different climatic states in this region may therefore improve our understanding of how large-scale circulation patterns could evolve under anthropogenically driven climate change. As a result of persistent arid conditions and lack of tectonic subsidence, evidence of fluvial and lacustrine activity has been destroyed, meaning terrestrial records of palaeoclimatic change in Australia are sparse. This study focuses on a marine core: Ocean Drilling Program (ODP) Hole 1195B on the Marion Plateau. Hole 1195B preserves an erosional and oceanographic record extending back to ~21 Ma and provides an opportunity to examine links between climate variability and continental weathering since the Middle Miocene.

This study employs XRF core scanning, GDGT biomarker analysis, and elemental analysis using ICP-OES. The results indicate that the highest delivery of clastic material to the Marion Plateau occurred during the Miocene Climatic Optimum (~17 Ma), coinciding with peak sea surface temperatures. The most pronounced cooling is observed between 11 and 9 Ma and was accompanied by significant changes in sediment input to the site. These changes were likely associated with shifts in Coral Sea circulation, potentially reflecting a strengthening of the East Australian Current. Notably, this regional response occurs ~2 Myr after the global cooling event observed elsewhere at ~13 Ma, suggesting that tropical climate systems may respond independently, or with some delay, in comparison to global climate perturbations. This highlights the importance of understanding climate dynamics in the tropics when considering potential future responses to anthropogenic climate change.

How to cite: McGanity-Smith, B., Clift, P. D., and Petrick, B.: Sediment cycling on the Marion Plateau since the Miocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10351, https://doi.org/10.5194/egusphere-egu26-10351, 2026.

Half-precession cycles (HPs), first identified in the 1980s, have been increasingly recognized as an important driver of tropical hydroclimate variability during the Quaternary. However, continuous long-term proxy records capturing their imprint on monsoon systems remain scarce. Here, we investigate the presence and evolution of HPs signals in a high-resolution inorganic geochemical record from ODP Site 663 (Eastern Equatorial Atlantic). This record provides a continuous perspective on West African Monsoon (WAM) variability over the last 1.2 Myr, spanning the Mid-Pleistocene Transition (MPT). Our results indicate that WAM variability during the MPT does not exhibit clear glacial–interglacial pacing. While this contrasts contemporaneous records from the Mediterranean and North Africa, the influence of the WAM becomes more pronounced after ~600 kyr, with intensified interglacial conditions and weaker glacial phases. In contrast, HPs show a stronger imprint on monsoon variability after the MPT, particularly during interglacial intervals. These findings are consistent with runoff records from the tropical American ICDP sites, suggesting a coherent low-latitude hydroclimate response. We propose that modulation of the Atlantic Meridional Overturning Circulation may provide a mechanistic link between HPs forcing, West African Monsoon variability, and tropical American precipitation.

How to cite: Martinez-Abarca, R., Ulfers, A., Zeeden, C., Westerhold, T., Vinnepand, M., De Vleeschouwer, D., Röhl, U., and Kaboth-Bahr, S.: Half-precession modulation of the West African Monsoon and possible links to continental hydroclimate records since the Mid-Pleistocene Transition., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21573, https://doi.org/10.5194/egusphere-egu26-21573, 2026.

The Trans-Amazon Drilling Project (TADP) provides a unique opportunity to investigate subsurface light-hydrocarbon dynamics in Amazonian sedimentary basins through the integration of continuous real-time gas monitoring during drilling, discrete gas sampling from sediment cores, and laboratory incubation experiments. This study combines gas geochemical data from Cenozoic sediments of the Acre Basin in western Amazonia and the Marajó Basin in eastern Amazonia, to characterize the occurrence, composition, origin, migration of light gaseous hydrocarbons, and potential microbial production of methane (CH₄), within continental siliciclastic successions, contributing to a refined understanding of subsurface carbon cycling.

In the Acre Basin, drilling penetrated a 923-m-thick sedimentary sequence dominated by interbedded claystones, siltstones, and sandstones. Continuous online gas analysis (OLGA) revealed CH₄ as the dominant hydrocarbon throughout the drilled profile, accompanied by recurrent detections of ethane (C₂H₆), propane (C₃H₈), iso-butane (i-C₄H₁₀), and n-butane (n-C₄H₁₀). Elevated concentrations of CH₄, C₂H₆, and C₃H₈ were preferentially associated with sandstone and siltstone layers sealed by claystones, indicating stratigraphic trapping of migrated gas. Bernard parameter values (CH₄/(C₂H₆+ C₃H₈)) range from 2 to 1904, reflecting strong compositional variability and mixing between gas sources. Carbon isotopic signatures of CH4 (δ¹³C- CH4 between −35‰ and −25‰ VPDB) indicate a dominant thermogenic contribution.

In the Marajó Basin, continuous gas monitoring during drilling to 924.3 m depth revealed higher? CH4 concentrations than in the Acre Basin with a general increase toward greater depths. Heavier hydrocarbons (C2–C4) show co-occurring concentration maxima indicating stratigraphically discrete gas migration and accumulation. CH₄ carbon isotopic compositions document a clear vertical transition in gas origin, from microbial hydrogenotrophic methanogenesis in the upper 250 m (δ¹³C- CH4 between −80‰ and −60‰), to mixed microbial–thermogenic gas between 250 and 300 m depth, and dominantly thermogenic gas below 300 m depth (δ¹³C- CH4 approaching −35‰), coinciding with increased C2–C4 concentrations.

Laboratory incubation experiments conducted on core sediment samples from both basins under anoxic conditions reveal a progressive increase in CH₄ concentrations over time, indicating active microbial methanogenesis. Incubation results show higher CH₄ yields in deeper samples, suggesting that, despite the strong influence of migrated thermogenic gas at depth, in situ microbial CH₄ production also contributes to the subsurface methane pool and is modulated by depth, substrate availability, and redox conditions.

Overall, the integrated results demonstrate that light hydrocarbon distributions in both basins are governed by the interaction between upward migration of thermogenic gas from deeper sources, stratigraphic trapping in permeable units sealed by fine-grained sediments, and active microbial processes identified through incubation experiments. The combined use of real-time gas monitoring, isotopic analyses, and incubation experiments provides a robust framework for disentangling gas origin and transformation processes, offering new insights into subsurface carbon cycling in Amazonian sedimentary basins.

How to cite: Martinez, A., Oliveira Sawakuchi, A., Oliveira Sawakuchi, H., Bertassoli Junior, D. J., Wiersberg, T., Tsai, S. M., Azevedo Bezerra, I. S., Noren, A., Guizan Silva, C., Fritz, S., and Baker, P. A.: Characterization of light hydrocarbons in subsurface Cenozoic sediments of western and eastern Amazonia drilled by the Trans-Amazon Drilling Project (TADP), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13841, https://doi.org/10.5194/egusphere-egu26-13841, 2026.

How to cite: Rulff, P., Abels, H., Fulton, P., and Bretaudeau, F. and the extended SEE-MORE team: Towards SEE-MORE - A multi-use borehole for optimisation of Subsurface Energy Exploration and MOnitoring of low-enthalpy geothermal REsources , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10916, https://doi.org/10.5194/egusphere-egu26-10916, 2026.

The C-Drill Core Repository, currently under development at the CNR - Territorial Research Area of Rome 1, is designed to address this gap by establishing a national reference facility for the conservation, management and scientific reuse of continental drilling cores. The repository will accommodate approximately 50–70 km of cores stored in controlled environments (+4 °C, room temperature, −20/−80 °C), supported by high-density mobile racking, automated climate control and continuous environmental monitoring. The facility will also host dedicated laboratories for core splitting and handling, high-resolution and multispectral imaging, XRF scanning, physical property logging (MSCL), wet and dry sample preparation, and microscopy. These capabilities will enable non-destructive characterisation and advanced analytical workflows directly linked to the archived materials.

A fully integrated digital workflow will be implemented, including systematic core digitisation, LIMS-based traceability, a standardised sample request system and interoperability with international data repositories in compliance with FAIR principles (e.g. PANGAEA, EarthChem, mDIS).

Conceived as a modular and scalable infrastructure, C-Drill will ensure high standards of climatic stability, data integrity, safety and user accessibility. The repository will provide services to national research institutes, universities and public agencies; support training activities for early-career scientists and technical staff; and generate interoperable datasets aligned with ICDP/IODP³, EPOS and other international frameworks.

By overcoming the current fragmentation of continental core archives in Italy, C-Drill will harmonise procedures for core acquisition, documentation and access with the best practices of leading European and international repositories. At the same time, it will enhance research efficiency, foster multidisciplinary collaboration and strengthen Italy’s capacity to participate in major international scientific drilling initiatives.

This contribution presents the design rationale, functional requirements, technological solutions and planned user services of the C-Drill Core Repository. The EGU platform will be used to engage potential partners, gather community feedback and refine the development roadmap towards full integration into the international scientific drilling network.

How to cite: Iadanza, A., Tentori, D., Mazzini, I., and Giaccio, B.: A national hub for continental scientific drilling: the C-DRILL core repository at CNR (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12539, https://doi.org/10.5194/egusphere-egu26-12539, 2026.