International Ocean Discovery Program (IODP) conducted a series of expeditions between 2014 and 2016 that were designed to address the development of monsoon climate systems in Asia and Australia. Significant progress was made in recovering Neogene sections spanning the region from the Arabian Sea to the Japan Sea and south to western Australia. High recovery by advanced piston core (APC) technology has provided a host of semi-continuous sections that have been used to examine monsoonal evolution. Use of half APC was successful in sampling sand-rich sediment in Indian Ocean submarine fans. The records show that humidity and seasonality developed diachronously across the region, although most regions show drying since the middle Miocene and especially since ~4 Ma, likely linked to global cooling. The transition from C3 to C4 vegetation often accompanied the drying, but may be more linked to global cooling. Western Australia, and possibly southern China diverge from the general trend in becoming wetter during the late Miocene, with the Australian monsoon being more affected by the Indonesian Throughflow, while the Asian Monsoon is tied more to the rising Himalaya in South Asia and to the Tibetan Plateau in East Asia. The monsoon shows sensitivity to orbital forcing, with many regions having a weaker summer monsoon during times of Northern Hemispheric Glaciation. Stronger monsoons are associated with faster continental erosion, but not weathering intensity, which either shows no trend or decreasing strength since the middle Miocene in Asia. Marine productivity proxies and terrestrial environmental proxies are often seen to diverge. Future work on the almost unknown Paleogene is highlighted, as well as the potential of carbonate platforms as archives of paleoceanographic conditions.

How to cite: Clift, P., Betzler, C., Clemens, S., Christensen, B., Eberli, G., France-Lanord, C., Gallagher, S., Holbourn, A., Kuhnt, W., Murray, R., Rosenthal, Y., Tada, R., and Wan, S.: A Campaign of Scientific Drilling for Monsoon Exploration in the Asian Marginal Seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1509, https://doi.org/10.5194/egusphere-egu22-1509, 2022.

Together with amphibole and garnet, epidote-group minerals are one of the three most important heavy minerals found in orogenic sediments (Garzanti and Andò, 2007). Their chemical composition and optical properties vary markedly with temperature and pressure conditions, and thus provide useful information in provenance analysis on the metamorphic grade of source rocks.

The aim of this study is to devise an efficient and quick method, with micrometric resolution to distinguish among the different species of the epidote group during routine point-counting of heavy-mineral slides, which can be applied on a vast ranges of grain-sizes from fine silt to medium sand.

The geochemical variability of epidote-supergroup minerals from different source rock collected in different sectors of the Alpine orogenic belt was first investigated by coupling Raman Spectroscopy, Scanning Electron Microscopy, and Energy-dispersed X-ray Spectroscopy (SEM-EDS). The geochemical composition, optical properties, and Raman fingerprints of these standard epidote grains were described and in-house database of Raman spectra was created, combining geochemical data and Raman response in the low wavenumbers region and OH stretching bands. A program, written in Matlab® language, has been established which allows to obtain a quick estimate of the amount of iron from the Raman spectra in the clinozoisite-epidote series.

Raman spectra of detrital epidotes contained in turbiditic sediments of the Bengal Fan (IODP Expedition 354) were next compared with Raman spectra of epidote-group standards to determine their composition. The identification and relative amount of detrital epidote, clinozoisite and zoisite in silt- and sand-sized deep-sea sediments contribute to constrain the metamorphic grade of Himalayan source rocks, reconstruct the erosional evolution of the Himalayan orogen, and provide information on climate change and strengthening of the Indian Ocean monsoon throughout the Neogene and Quaternary.

Key words: epidote, provenance, Himalaya, Raman spectroscopy, Microprobe analyses, optical microscope.

Garzanti, E., Andò S., 2007. Plate tectonics and heavy-mineral suites of modern sands. In: Mange, M.A., Wright, D.T. (Eds.), Heavy Minerals in Use, Developments in Sedimentology Series, 58. Elsevier, Amsterdam, pp. 741-763.

How to cite: Limonta, M., Andò, S., Bersani, D., France-Lanord, C., and Garzanti, E.: Raman identification of epidote-group minerals in turbiditic sediments from the Bengal Fan (IODP Exp. 354): a complementary tool to better constrain metamorphic grade of source rocks., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6161, https://doi.org/10.5194/egusphere-egu22-6161, 2022.

The Main Zone of the Bushveld Complex in South Africa is the most voluminous but least studied part of the world’s largest igneous intrusion. Modal layering is poorly developed compared with the units above and below (Upper and Critical Zones, resp.), and most of the ca. 3000 meter-thick Main Zone consists of monotonous gabbronorite, occasionally grading into norite and anorthosite. An exception is the ultramafic “Pyroxenite Marker” near the top of the Main Zone, which is present regionally in the complex and represents a major event of magma recharge into the chamber. However, studies of drillcore through the Main Zone in the Bushveld Northern limb (Ashwal et al., 2005; Hayes et al., 2017) found evidence for layering by periodic variations in rock density at vertical length-scales of 40 to 170 m. This implies there were many more episodes of magma recharge than previously thought.

Our study in the Eastern Limb of the complex tests if cryptic layering in the Main Zone is a local phenomenon or is regionally developed like the Pyroxenite Marker. The first step, reported here, was a vertical profile of bulk density data (Archimedes method) for a 1450 m section of the upper Main Zone below the Pyroxenite Marker. Samples were taken at 1 to 5 m intervals and the results show several intervals of density variations at length-scales of 30 to 120 m, comparable to those previously described in the Northern Limb. Periodicity in density changes is not so well developed as in the earlier study, and we identified several 50 to 75 m intervals where density variations are below 0.05 g/cm³. The second step of the study will use multispectral and laser-induced breakdown spectroscopy (LIBS) scanning to provide modal mineralogy profiles of the same drillcore samples used for density measurement. After cryptic modal layering is documented in this way, follow-up petrologic-geochemical studies at the layer boundaries will aim to characterize the composition and temperature of the magmas involved.

For this project the Bushveld Complex Drilling Project (BVDP) provided access to the BH7771 borehole, donated by Impala Platinum’s Marula mine.

References:

Ashwal, L..D., Webb, S.J. and Knoper, M.W. (2005) S. Afr. Jour. Geol., 108, 199-232.

Hayes, B., Ashwal, L.D., Webb, S.J. and Bybee, G.M. (2017) Contrib. Mineral. Petrol., 172, 13.

How to cite: Trumbull, R. B., Veksler, I. V., Nikonov, W., and Rammlmair, D.: How was the Bushveld Complex assembled? A search for cryptic layering in ICDP drillcores from the Main Zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8339, https://doi.org/10.5194/egusphere-egu22-8339, 2022.

A 6-meter drill core from Merensky Reef, Bushveld Complex, South Africa, was scanned in detail with a drill core scanner based on Laser Induced Breakdown Spectroscopy (LIBS). The purpose of the investigation was to visualize variations in the chemical composition along the core, and following a mineral classification of the LIBS data, of variations in the mineral chemical composition, e.g. of Fe/Mg, Cr/Al, and Ca/Na ratios, as well.

The LIBS technology is based on atomic emission spectroscopy, in which the excitation of the atomic species occurs in-situ on the sample surface. The excitation source was a pulsed 50 mJ 1064 nm Nd:YAG laser, and the emitted light was collected with a high-resolution wide-range echelle spectrograph with CCD detector. This approach for measuring mineral chemical ratios such as Mg/Fe, Cr/Al, and Ca/Na, is based on the strength of LIBS in detecting chemical variations using intensity ratios within a single matrix, which in this application is one single particular type of mineral phase. For validation purposes, selected samples were analysed with bulk chemical analysis and electron probe microanalysis as well.

Distinct trends could indeed be extracted from the 6 m core section through the Merensky Reef. From a saw-cut core surface without further preparation, a continuous record could be extracted consisting of Mg/Fe of orthopyroxene, Ca/Na of plagioclase, bulk chemical patterns, modal composition, and direct neighbourhood. The data can be used to highlight the presence of unusual patterns and to relate them to Ni, Cu, PGE or other mineralization. When applied to different core sections, it may become an important tool for comparing lateral variability of diagnostic horizons in vertical sequences in layered intrusions such as Merensky Reef and UG-2.

How to cite: Meima, J., Rammlmair, D., Junge, M., and Nikonow, W.: Continuous measurement of Mg/Fe and Ca/Na ratios with scanning Laser Induced Breakdown Spectroscopy in 6 meter of drill core through Merensky Reef, Bushveld Complex, South Africa , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7513, https://doi.org/10.5194/egusphere-egu22-7513, 2022.

The Oman Ophiolite is the largest and best-investigated piece of ancient oceanic lithosphere on our planet. This ophiolite was target of the Oman Drilling Project (OmanDP) within the frame of ICDP (International Continental Scientific Drilling Program) which aimed to establish a comprehensive drilling program in order to understand essential processes related to the geodynamics of mid-ocean ridges, as magmatic formation, cooling/alteration by seawater-derived fluids, and the weathering with focus on the carbonatisation of peridotites.

Over two drilling seasons, the OmanDP has sampled the Samail Ophiolite sequence from crust to basal thrust. The total cumulative drilled length is 5458 m, with 3221 m of which was at 100% recovery. These cores were logged to IODP standards aboard the Japanese drilling vessel Chikyu during two description campaigns in summer 2017 and 2018. 

Here we present the main results of the working groups of the Universities Hannover and Kiel, focusing on the magmatic accretion of the Oman paleoridge. During 5 field campaigns these groups established a 5 km long profile through the whole crust of the Oman ophiolite by systematic outcrop sampling, providing the reference frame for the 400 m long OmanDP drill cores. The profile contains 463 samples from the mantle, through gabbros up to the dike/gabbro transition. Identical samples have been analyzed by several methods (bulk rock geochemistry, mineral analysis, Isotope geochemistry, EBSD analysis).

The results allow implication on the mechanism of accretion of fast-spreading lower oceanic crust. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast-spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on-axis at very high temperatures.

How to cite: Koepke, J., Garbe-Schönberg, D., Mock, D., and Müller, S.: A profile through fast-spreading oceanic crust in the Oman ophiolite: reference frame for the crustal drillings within the ICDP Oman Drilling Project , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10040, https://doi.org/10.5194/egusphere-egu22-10040, 2022.

DeepStor-1 is the exploration well to the Helmholtz research infrastructure "DeepStor". DeepStor focuses on the investigation of high-temperature heat storage at the rim of the fromer oil-field „Leopoldshafen“. It is located about 10 km north of the city of Karlsruhe (Germany). The DeepStor-1 well is planned to reach the Pechelbronn group at 1‘460 m, i.e. it includes nearly the entire Oligocene sediments at the site. Seismic investigation reveal a structurally undisturbed section that below 200 m depth covers the Landau, Bruchsal, Niederrödern and Froidefontaine Formations. Cores will be taken from the entire section below 820 m. In addition to coring, the logging program is planned to include besides technical logging, a caliper-, self-potential-, temperature-, dual latero-, natural gamma spectrometry-, neutron-gamma porosity-, sonic-, elemental capture spectroscopy-, as well as image-logs in the sections 215-820 m as well as 820-1460 m. Drilling of DeepStor-1 is planned between 2022 and 2023.

How to cite: Eva, S., Bauer, F., Steiner, U., Frieg, B., and Kohl, T.: DeepStor-1 exploration well at KIT Campus North (Upper Rhine Graben, Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-640, https://doi.org/10.5194/egusphere-egu22-640, 2022.

The Late Miocene deposits in the Sorbas Basin (Spain) have been of an extreme importance in the understanding of the Messinian Salinity Crisis (MSC) events (5.97-5.33 Ma). They consist of four formations. The pre-crisis Abad marls topped by the evaporitic Yesares gypsum member, followed by two non-evaporitic units known as the Sorbas and Zorreras members. Those deposits have been widely explored and studied thanks to the numerous outcropping sections in the basin.

The ‘SaltGiant’ European Training Network held a training school in October 2021 in the Sorbas Basin, where four boreholes (named SG0, 1, 2 and 3) covering most of the Messinian Salinity Crisis sequence, were drilled, cored and logged in this context along an overall thickness of about 175 m. The drillings took place inside and in the vicinity of the Torralba gypsum mine. It allowed for the first time in the scientific non-industrial domain, access to a continuous and non-outcropping succession of the Messinian deposits in the Sorbas basin. In addition to the recovered cores, borehole geophysical data were obtained from the four holes and digital images of the area were collected with a drone. Prior to the drilling, an OBO (Outcrop / Behind Outcrop) workflow was followed, which will allow integrating the outcrop and subsurface data by combining the 3D geometry of geobodies with geophysical information.

Optical borehole wall images provide mm-scale images of the borehole walls, highlighting the sedimentological and structural characteristics of the deposits. Downhole geophysical measurements included acoustic velocity, electrical resistivity and natural spectral gamma ray, which allowed determining the petrophysical characteristics of the penetrated lithologies. In addition to the petrophysical logs, a Vertical Seismic Profiling was performed in holes SG2 and SG3, including a multi-offset VSP survey in hole SG3.

The petrophysical characterization of the Messinian deposits will provide a reference case study for the lithologic characterization of MSC deposits in the subsurface elsewhere. VSP analysis provided an in-field preliminary seismic velocity evaluation in the encountered formations. Preliminary results confirm the astronomical precession-driven cyclicity observed elsewhere in the Messinian gypsum. Further processing and analyses of the large amount of acquired data will lead to identifying the astronomical and possibly higher-frequency cyclicity in the post-evaporitic deposits in the Sorbas member.

How to cite: Raad, F., Pezard, P., Viseras, C., Sierro, F. J., Yeste, L. M., Aguila, J. J., Jerez, P., Schleifer, A., Meneghini, F., Bellezza, C., Lofi, J., Camerlenghi, A., and Aloisi, G.: ‘SaltGiant’ drilling in the Sorbas Basin: Structural, Petrophysical and Geochemical characterization of the Messinian Salinity Crisis deposits, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8952, https://doi.org/10.5194/egusphere-egu22-8952, 2022.

Sulfate reduction is the quantitatively most important process to degrade organic matter in anoxic marine sediment and has been studied intensively in a variety of settings. Guaymas Basin, a young marginal ocean basin, offers the unique opportunity to study sulfate reduction in an environment characterized by organic-rich sediment, high sedimentation rates, and high geothermal gradients (100-958°C km^-1). We measured sulfate reduction rates (SRR) in samples of the International Ocean Discovery Program (IODP) Expedition 385 using incubation experiments with radiolabeled ³⁵SO₄^2- carried out at in-situ pressure and temperature. Site U1548C, outside of a circular hydrothermal mound above a hot sill intrusion (Ringvent), has the highest geothermal gradient (958°C km^-1) of all eight sampling sites. In near-surface sediment from this site, we measured the highest SRR (387 nmol cm^-3 d^-1) of all samples from this expedition. At Site U1548C SRR were generally over an order of magnitude higher than at similar depths at other sites. Site U1546D also had a sill intrusion, but it had already reached thermal equilibrium and SRR were in the same range as nearby Site U1545C, which is minimally affected by sills. The wide temperature range found in the stratigraphic section at each drill site leads to major shifts in microbial community composition with very different temperature optima. At the transition between the mesophilic and thermophilic range around 40 to 60°C, sulfate-reducing activity appears to be decreased, particularly in more oligotrophic settings but shows a slight recovery at higher temperatures.

How to cite: Nagakura, T., Schubert, F., and Kallmeyer, J. and the IODP Exp. 385 Scientists: Biological sulfate reduction in deep subseafloor sediment of Guaymas Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2525, https://doi.org/10.5194/egusphere-egu22-2525, 2022.

A fourth of the global seabed sediment volume is buried at depths where temperatures exceed 80 °C, a previously proposed thermal barrier for life in the subsurface. Here, we demonstrate, utilizing an extensive suite of radiotracer experiments, the prevalence of active methanogenic and sulfate-reducing populations in deeply buried marine sediment from the Nankai Trough subduction zone, heated to extreme temperature (up to ~120 °C). Sediment cores were recovered during International Ocean Discovery Program (IODP) Expedition 370 to Nankai Trough, off the cost of Moroto, Japan. The steep geothermal gradient of ~100 °C km^-1 allowed for the exploration of most of the known temperature range for life over just 1 km of drill core. Despite the high temperatures, microbial cells were detected almost throughout the entire sediment column, albeit at extremely low concentration of <500 cells per cm³ in sediment above ~50 °C. In millions of years old sediment a small microbial community subsisted with high potential cell-specific rates of energy metabolism, which approach the rates of active surface sediments and laboratory cultures. Even under the most conservative assumptions, potential biomass turnover times for the recovered sediment ranges from days to years and therefore many orders of magnitude faster than in colder deep sediment.

Our discovery is in stark contrast to the extremely low metabolic rates otherwise observed in the deep subseafloor. As cells appear to invest most of their energy to repair thermal cell damage in the hot sediment, they are forced to balance delicately between subsistence near the upper temperature limit for life and a rich supply of substrates and energy from thermally driven reactions of the sediment organic matter.

How to cite: Schubert, F., Beulig, F., Adhikari, R. R., Glombitza, C., Heuer, V., Hinrichs, K.-U., Homola, K., Inagaki, F., Jørgensen, B. B., Kallmeyer, J., Krause, S., Morono, Y., Sauvage, J., Spivack, A., and Treude, T.: Microbial survival through high metabolic rates in a deep and hot subseafloor environment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2909, https://doi.org/10.5194/egusphere-egu22-2909, 2022.

International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology (offshore period: 13 April to 1 June 2021; Onshore Science Party: 14 February to 14 March 2022) was designed to test the concept of submarine paleoseismology in the Japan Trench, the area where the last, and globally only one out of four instrumentally-recorded, giant (i.e. magnitude 9 class) earthquake occurred back in 2011. “Submarine paleoseismology” is a promising approach to investigate deposits from the deep sea, where earthquakes leave traces preserved in the stratigraphic succession, to reconstruct the long-term history of earthquakes and to deliver observational data that help to reduce uncertainties in seismic hazard assessment for long return periods. This expedition marks the first time, giant piston coring (GPC) was used in IODP, and also the first time, partner IODP implementing organizations cooperated in jointly implementing a mission-specific platform expedition.

We successfully collected 29 GPCs at 15 sites (1 to 3 holes each; total core recovery 831 meters), recovering 20 to 40-meter-long, continuous, upper Pleistocene to Holocene stratigraphic successions of 11 individual trench-fill basins along an axis-parallel transect from 36°N – 40.4°N, at water depth between 7445-8023 m below sea level. These offshore expedition achievements reveal the first high-temporal and high spatial resolution investigation and sampling of a hadal oceanic trench, that form the deepest and least explored environments on our planet.

The cores are currently being examined by multimethod applications to characterize and date hadal trench sediments and extreme event deposits, for which the detailed sedimentological, physical and (bio-)geochemical features, stratigraphic expressions and spatiotemporal distribution will be analyzed for proxy evidence of giant earthquakes and (bio-)geochemical cycling in deep sea sediments. Initial preliminary results presented in this EGU presentation reveal event-stratigraphic successions comprising several 10s of potentially giant-earthquake related event beds, revealing a fascinating record that will unravel the earthquake history of the different along-strike segments that is 10–100 times longer than currently available information. Post-Expedition research projects further analyzing these initial IODP data sets will (i) enable statistically robust assessment of the recurrence patterns of giant earthquakes, there while advancing our understanding of earthquake-induced geohazards along subduction zones and (ii) provide new constraints on sediment and carbon flux of event-triggered sediment mobilization to a deep-sea trench and its influence on the hadal environment.

How to cite: Strasser, M., Ikehara, K., Everest, J., and Maeda, L. and the IODP Expedition 386 Science Party: IODP Expedition 386 “Japan Trench Paleoseismology”: Mission Specific Platform Giant Piston Coring to track past megathrust earthquakes and their consequences in a deep-sea subduction trench. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1729, https://doi.org/10.5194/egusphere-egu22-1729, 2022.

The Main Marmara Fault (MMF) in NW Turkey south of Istanbul is a segment of the North Anatolian Fault Zone (NAFZ) that constitutes a right-lateral continental transform fault.  Several well-documented strong (M7+) earthquakes indicate that the MMF poses a great risk to the Istanbul metropolitan region. A 150 km long stretch of the MMF has not ruptured since 1766 and the recurrence time of 250 yrs for M7+ events derived from historical records indicate that the fault is overdue. We introduce a new project addressing how the rheological configuration of the lithosphere in concert with active fluid dynamics within the crust and mantle influence the present-day deformation along the MMF in the Marmara Sea region. We test the following hypotheses: (1) the seismic gap is related to the mechanical segmentation along the MMF which originates from the rheological configuration of the crust and lithosphere; (2) variations in deformation mechanisms with depth in response to variations in temperature and (fluid) pressure exert a first-order control on the mode of seismic activity along the MMF, and, (3) stress and strain concentrations due to strength and structural variability along the MMF can be used as an indicator for potential nucleation areas of expected earthquakes. To assess what mechanisms control the deformation along the MMF, we use data from the ICDP GONAF observatory (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) and a combined work flow of data integration and process modelling to derive a quantitative description of the physical state of the MMF and its surrounding crust and upper mantle. Seismic and strain observations from the ICDP-GONAF site are integrated with regional observations on active seismicity, on the present-day deformation field at the surface, on the deep structure (crust and upper mantle) and on the present-day stress and thermal fields. This will be complemented by numerical forward simulations of coupled thermo-hydraulic-mechanical processes based on the observation-derived 3D models to evaluate the key controlling factors for the present-day mechanical configuration of the MMF and to contribute to a physics-based seismic hazard assessment.

How to cite: Scheck-Wenderoth, M., Cacace, M., Heidbach, O., Bohnhoff, M., Nurlu, M., Fernandez Terrones, N., Bott, J., and Gholamrezaie, E.: Deformation mechanisms along the Main Marmara Fault around the ICDP-site GONAF, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3538, https://doi.org/10.5194/egusphere-egu22-3538, 2022.

At the Hikurangi convergent margin the Pacific plate is subducted westward beneath the Australian plate. This margin has been the location of major earthquakes as well as slow slip events related to the ongoing subduction. Drill site U1518 which was drilled during IODP Expedition 375, 73 km offshore Gisborne (New Zealand), targeted the Papaku fault, a splay fault of the major decollement in sediments of the frontal accretionary prism. We selected samples from the mostly hemipelagic, weakly consolidated mudstones in the fault zone, as well as from hangingwall and footwall. In order to investigate localized and distributed deformation in the fault zone, we analysed composition, microstructure and crystallographic preferred orientation (CPO). For that we applied µXRF measurements and optical microscopy, as well as synchrotron texture analysis at DESY in Hamburg.

The samples from hanging- and footwall sediments show a relatively homogeneous microstructure with local compositional layering. While CPO strength in the hangingwall is slightly increasing with depth for all analysed clay mineral phases, the CPO in the footwall samples is in general lower and does not show a clear trend with depth. This might be interpreted as different deformation histories in hangingwall and footwall which is in accordance with previous studies. Fault zone samples show a variety of microstructures, such as mingling of different sedimentary components, locally overprinted by microfaults. CPO strength in the faulted sediments is also variable, with zones showing strong alignment of phyllosilicates and zones showing weak alignment of phyllosilicates. Variations in CPO and variable distribution of sedimentary components indicate a heterogeneous deformation within the fault zone which might be due to local compositional variations.

How to cite: Kühn, R., Greve, A., Kilian, R., Mizera, M., and Stipp, M.: Heterogeneous deformation across the Papaku fault, Hikurangi accretionary prism , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11265, https://doi.org/10.5194/egusphere-egu22-11265, 2022.

The global reservoir of submarine gas hydrates is favored by the cold temperature of oceanic bottom water and the generally low geothermal gradients along passive continental margins. The continental margins of the land-locked Mediterranean basin are a remarkable exception for the lack of evidence of extensive presence of gas hydrates. Using public data of the physics and chemistry of the subsurface available from 44 Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) wells as lithologic logs, downhole temperature measurements, and pore water salinity values, and observed physical characteristics of bottom waters, we model the theoretical methane hydrate stability zone (MHSZ) below the seafloor and in the water column.

We find important positive pore water salinity anomalies in the subsurface indicating the pervasive presence of concentrated brines up to saturation concentration of halite and gypsum (> 300 ‰). The resulting sub-bottom MHSZ is thinner by up to 90-95% with respect to its thickness calculated assuming constant salinity with depth equal to bottom waters salinity. In the Eastern Mediterranean deep basins the thickness of the subsurface MHSZ is largest (up to ~ 350 m) and the anomaly induced by subsurface brines is highest (~ -300 m), while in the Alboran, Western Mediterranean, Tyrrhenian, Sicily Channel, Adriatic and Aegean basins the MHSZ, where present, thins to less than 100 m with mostly negligible anomaly induced by the presence of subsurface brines.

Modelling results suggest that subsurface brines can produce dramatic reductions of the thickness of the MHSZ only where the geothermal gradient is low (Eastern Mediterranean). We have modelled the same brine-induced limiting effect on the thickness of the MHSZ in synthetic cases of high and low heat flow to simulate Western and Eastern Mediterranean subsurface thermo-haline conditions. The salinity effect is attenuated by the thermal effect in the Western Mediterranean that produces the most relevant thinning of the MHSZ.

The distribution of the MHSZ resulting from the modelling coincides well with the distribution of the Late Miocene salt deposits which limit further the possibility of formation of gas hydrates acting as low permeability seal to the up-ward migration of hydrocarbon gases.

This modelling exercise provides a robust explanation for the lack of evidence of widespread gas hydrates on Mediterranean continental margins, with the exception of areas of local methane upward advection such as mud volcanoes, and it outlines a number of local hydrate-limiting factors that make this basin unfavorable to gas hydrate occurrence.

How to cite: Corradin, C., Camerlenghi, A., Giustiniani, M., Tinivella, U., and Bertoni, C.: Legacy DSDP and ODP data suggest a paradigm shift in methane hydrate stability in the Mediterranean Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3793, https://doi.org/10.5194/egusphere-egu22-3793, 2022.

Insights into the climate variability of western Africa during the Pleistocene epoch have thus far been limited by the lack of well-dated, high-resolution terrestrial climate archives. The missing information on the climate evolution of western African hampers our understanding of the proposed pan-African evolution of our species. The ~294 m lacustrine sedimentary sequence raised from Lake Bosumtwi by the International Continental Drilling program in 2004, encompassing the last ~1.1 Ma, offers the best opportunity provide a climatic benchmark record in western Africa. However, the establishment of a chronology for this record has proven challenging. To try and improve our understanding of the climatic evolution during the last ~1.1 Ma in western Africa, we will use the high-resolution downhole logging data (natural gamma ray, GR) and magnetic susceptibility data from core logging from Site 5, which is situated in the centre of Lake Bosumtwi. To maximise the robustness of this record we will try to correlate data from downhole logs with core data. This approach has help improve interpretation of logging signals and environmental reconstructions for other long lake records, such as e.g. Lake Ohrid.

How to cite: Zeeden, C., Vinnepand, M., Kaboth-Bahr, S., Gosling, W., Kück, J., and Wonik, T.: Assessing the well logging data from the Lake Bosumtwi (Ghana), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10406, https://doi.org/10.5194/egusphere-egu22-10406, 2022.

The Izu-Bonin Mariana (IBM) convergent margin is located in the NW Pacific Ocean (12° N to 35° N) and represents, to the best of our knowledge, the only setting where recent episodes of serpentinite mud volcanism took place. The IBM arc-system started to form around 50-52 Ma when the Pacific Plate began to subside below the Philippine Plate and the eastern Eurasian Margin. On the Mariana forearc system, which constitutes the southward region of the IBM, a high number of large serpentinite mud volcanoes formed between the trench and the Mariana volcanic arc. Their origin is linked to episodic extrusion of serpentinite mud and fluids along with materials from the upper mantle, the Philippine plate, and the subducting Pacific plate to the sea floor, through a system of forearc faults. Among them, Fantangisña seamount was drilled during IODP Expedition 366. Cored material comprises serpentinite mud and ultramafic clasts that are underlain by nannofossil-rich forearc deposits and topped by pelagic sediments.

Integrated calcareous nannofossil and planktonic foraminifera biostratigraphy was performed on Sites U1497 and U1498, which are at the top of the serpentinite seamount and on its most stable southern flank, respectively. A total of nine bioevents were recorded in this study, permitting the establishment of a valid age-depth model for Site U1498A which allows for the definition of the latest phase of activity of Fantangisña serpentinite mud volcano. In particular, the emplacement of the mud production was detected between 6.10 (Late Miocene, Messinian) to 4.20 (Early Pliocene, Zanclean). This time interval is defined by nannofossil bioevents LO Reticulofenestra rotaria and FO of Discoaster asymmetricus. Furthermore, our analyses reveal that the latest stage of the serpentinite mud activity occurred 4 Ma later than the age proposed by a previous study (10.77 Ma) and is coeval with the initiation of the rifting in the Mariana Trough recorded at 7-6 Ma.

The age depth model also shows a rapid shift in sedimentation rates (11.80 to 94.71 m/Myr) during the Middle Pleistocene, which corresponds to a change in deposition of distinct serpentinite mud units, likely associated with the regional tectonic activity (different stages of seamount accretion and subduction and/or changes in the forearc extension related to the slab rollback).

How to cite: Del Gaudio, A. V., Piller, W. E., Auer, G., and Kurz, W.: Dating the serpentinite mud production of Fantangisña seamount using calcareous nannofossils and planktonic foraminifera biostratigraphy (IODP Expedition 366)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1019, https://doi.org/10.5194/egusphere-egu22-1019, 2022.

The Arctic is both a contributor to climate change and a region that is most affected by global warming. Despite this global importance, the Arctic Ocean is the last major region on Earth where the long-term climate history remains poorly known. Major advances in understanding were achieved in 2004 with the successful completion of IODP Expedition 302: Arctic Coring Expedition – ACEX – implemented by ECORD, marking the start of a new era in Arctic climate exploration. Although the ACEX results were unprecedented, key questions related to the Cenozoic Arctic climate history remain unanswered, largely due to a major mid-Cenozoic hiatus (or condensed interval) and partly to the poor recovery of the ACEX record. Building on ACEX and its cutting-edge science, IODP Expedition 377: Arctic Ocean Paleoceanography (ArcOP) has been scheduled for mid-August to mid-October 2022. The overall goal of ArcOP is the recovery of a complete stratigraphic sedimentary record on the southern Lomonosov Ridge to meet the highest priority paleoceanographic objective: the continuous long-term Cenozoic Arctic Ocean climate history with its transition from the early Cenozoic Greenhouse world to the late Cenozoic Icehouse world. Furthermore, sedimentation rates two to four times higher than those of ACEX will permit higher-resolution studies of Arctic climate change in the Neogene and Pleistocene. Key objectives are related to the reconstruction of the history of circum-Arctic ice-sheets, sea-ice cover, Siberian river discharge, and deep-water circulation and ventilation and its significance within the global climate system. Obtaining a geologic record of a 50-60 million year time span will provide opportunities to examine trends, pat­terns, rates, causes, and consequences of climate change that are important and relevant to our future. This goal can be achieved through (i) careful site selection, (ii) the use of appropriate drilling technology and ice management, and (iii) applying multi-proxy approaches to paleoceanographic, paleoclimatic, and age-model reconstructions.

In August 2022, a fleet of three ships, the drilling vessel “Dina Polaris” and the powerful icebreakers “Oden” and “Viktor Chernomyrdin”, will set sail for a location on Lomonosov Ridge in international waters far from shore (81°N, 140°E; 800-900 m of water depth). There, the expedition will complete one primary deep drill site (LR-11B) to 900 meters below seafloor (mbsf) which is twice that of the ACEX drill depth – certainly a challenging approach. Based on detailed site survey data, about 230 m of Plio‐Pleistocene, 460 m of Miocene, and >200 m of Oligocene‐Eocene sedimentary sequences might be recovered at this site. In addition, a short drill site (LR-10B) to 50 mbsf will be supplemented to recover an undisturbed uppermost (Quaternary) sedimentary section to ensure complete recovery for construction of a composite section spanning the full age range through the Cenozoic.

In this talk, background information, scientific objectives and an update of the status of planning and implementation of the ArcOP Expedition will be presented. For further details we refer to the ArcOP Scientific Prospectus (https://doi.org/10.14379/iodp.sp.377.2021).

How to cite: Stein, R., St.John, K., and Everest, J.: The Cenozoic Arctic Climate and Sea Ice History - Scientific objectives, challenges and implementation update of IODP Expedition 377 (ArcOP), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1277, https://doi.org/10.5194/egusphere-egu22-1277, 2022.

The NE Atlantic conjugate volcanic rifted margins are characterized by extensive breakup-related magmatism recorded by basalt flows, volcanogenic sediments, magmatic underplates, and intrusive complexes in sedimentary basins and the crust. Onset of this voluminous magmatism is concomitant with the global hot-house climate in the Paleogene, and the injection of magma into organic-rich sedimentary basins is a proposed mechanism for triggering short-term global warming during the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma).

The aims of IODP Exp. 396 (August-September 2021) were to drill three transects on the mid-Norwegian continental margin to sample 1) hydrothermal vent complexes formed by eruption of hot fluids and sediments above sill intrusions (Modgunn Transect), 2) Paleogene sediments, with particular focus on the Paleocene-Eocene transition (Mimir Transect), and 3) basalt and sub-basalt sequences across the volcanic rifted margin and the initial oceanic crust (Basement Transect). A total of 21 boreholes were drilled, successfully coring all nine primary and one alternate sites. A comprehensive suite of wireline logs was collected in eight boreholes. Most of the sites were located on industry-standard 3D seismic reflection data, whereas additional high-resolution 2D and 3D P-Cable site survey data were acquired across six sites which were highly useful during the Mimir and Modgunn transect drilling. In total, more than 2000 m of core were recovered during 48 days of operations, including more than 350 m of basalt, 15 m of granite, and 900 m of late Paleocene to early Eocene sediments. Drilling was done using a combination of RCB, XCB, and APC drill bits, commonly with half-advances (c. 5 m) to optimize core recovery. Particularly high recovery (almost 100%) was obtained by half-length APC coring of Eocene sediments in two holes on the outer Vøring Margin, whereas basaltic basement recovery was above 60% in seven holes.

Expedition 396 probed the key elements of a typical volcanic rifted margin and the associated sedimentary archive. Of particular importance is the Modgunn Transect, where we drilled five holes through the upper part of a hydrothermal vent complex with a very expanded Paleocene-Eocene Thermal Maximum (PETM) interval dominated by biogenic ooze and volcanic ash deposits. The expedition also recovered an unprecedented suite of basalt cores across a volcanic rifted margin, including both subaerial and deep marine sheet flows with inter-lava sediments and spectacular shallow marine pillow basalts and hyaloclastites, as well as high-resolution interstitial water samples to assess sediment diagenesis and fluid migration in the region. Lastly, we recovered the first cores of sub-basalt granitic igneous rocks and upper Paleocene sediments along the mid-Norwegian continental margin. Collectively, this unique sample archive offers unprecedented insight on tectonomagmatic processes in the NE Atlantic, and links to rapid climate evolution across the Cenozoic.

How to cite: Planke, S., Berndt, C., Huismans, R., Buenz, S., Alvarez Zarikian, C. A., and Scientists, E.: Operations and Initial Results from IODP Expedition 396: Mid-Norwegian Continental Margin Magmatism and Paleoclimate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1917, https://doi.org/10.5194/egusphere-egu22-1917, 2022.

The innovative, new drilling technique of the Hipercorig platform (Harms et al., 2020, https://doi.org/10.5194/sd-28-29-2020) enables to recover undisturbed long cores of sediment archives, and hence allows us to study past environmental conditions and changes. Here we present initial results from the Hipercorig Hallstatt History (H³) lake drilling campaign 2021, which succeeded to recover two parallel cores (core A: 41m, core B: 51m) from 122 m water depth providing a high-resolution record, within the UNESCO World Heritage Cultural Landscape Hallstatt-Dachstein/Salzkammergut, Austria. The Hallstatt-Dachstein region has a history of over 7,000 years of human salt mining and is one of the oldest documented cultural landscapes worldwide.

We present physical- and litho-stratigraphy based on borehole logging (of hole B), non-destructive core logging data, visual core and lithofacies description, Core-Log-Seismic-Correlation and initial age modelling using ¹⁴C dating. The core logging covers (i) x-ray computed tomography, (ii) multi-sensor-core-logger data with Gamma-Ray attenuated bulk density, magnetic susceptibility and visible light photo spectroscopy. The upper ~15 m of the sediment profile can be unambiguously correlated with previous cores (Lauterbach et al., submitted) thus confirming that the sediments are truly representative for Lake Hallstatt. The entire stratigraphic succession comprises two major lithostratigraphic units: The Holocene unit (0-40 m below lake floor (mblf)) and the Late Pleistocene unit (> 40 m). The Holocene unit consists of variably laminated (sub-mm to 5 mm) dark gray clayey-silty carbonate mud interbedded with up to 5.5 m thick mass-movement deposits and thick turbidites. The Late Pleistocene sedimentary succession comprises very thin bedded (1-3 cm) medium gray silty clayey carbonate mud, with some laminated (<1 cm) intervals and multiple cm-thick light gray turbidites. Within the Late Holocene unit, there is a prominent yellowish gray clastic interval of ~4 m with faintly mm- to cm-scale laminated sediments. Another remarkable characteristic of the Holocene unit is the occurrence of at least four major mass-movement deposits containing pebbles (up to 3 cm in diameter) and six thick turbidite deposits >1 m with different sediment colors and compositions.

Detailed multi-proxy analyzes of the Lake Hallstatt cores will provide new insights into the early history of human settlement and salt mining in this Alpine region and their relation to environmental and climatic conditions and meteorological and geological extreme events.

How to cite: Ortler, M., Brauer, A., Fabbri, S. C., Kowarik, K., Kueck, J., and Strasser, M.: Hipercorig Hallstatt History (H3) reveals a high-resolution Late Pleistocene to Holocene sediment record at Lake Hallstatt (Salzkammergut, Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3428, https://doi.org/10.5194/egusphere-egu22-3428, 2022.

The sedimentary infill of glacially overdeepened valleys (i.e. eroded structures below the fluvial base level) are, together with glacial geomorphology, the best-preserved (yet underexplored) direct archives of extents and ages of past glaciations in and around mountain ranges. ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase-1 investigates five drill cores from glacially overdeepened structures at several complementing locations along the northern front of the Alps and their foreland. Two of these drill sites, both in the former reaches of the Rhine Glacier, have been successfully drilled in 2021 with excellent core recovery of 95 %: i) The borehole in Basadingen in Northern Switzerland reached a depth of 253 m, and ii) The Tannwald site in Southern Germany consists of one cored borehole to 165 m and two nearby flush boreholes; all three sites will allow a series of crosshole geophysical experiments. Three previously drilled legacy cores from the Eastern Alps are included in the DOVE Phase-1: iii) a core from Schäftlarn, located in the Isar-Loisach glacier catchment, was drilled in 2017 down to a depth of 199 m; iv) the Neusillersdorf drill site, located in the southern German Salzach Foreland glacier area, recovered a sequence down to 136 m (incl. 116 m of Quaternary strata); and v) the drill site Bad Aussee in Austria is located in the area of the Traun Glacier at an inneralpine location. It recovered almost 900 m of Quaternary sediments.

All the sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. For example, the geometry of overdeepened structures will be investigated using different geophysical approaches (e.g. seismic surveys) to better understand the process of overdeepening. Sedimentological analyses in combination with downhole logging, investigation of biological remains and state-of-the-art geochronological methods will allow to reconstruct the filling and erosion history of the troughs. We expect significant and novel data relating to the extent and timing of the past Alpine glaciations during the Middle-to-Late Quaternary glacial-interglacial cycles. Besides these basic scientific goals, this proposal also addresses a number of applied objectives such as groundwater resources, geothermal energy production, and seismic hazard assessment.

A successful DOVE Phase-1 will lay the ground for an upcoming Phase-2 that will complete the panalpine approach. This follow-up phase will investigate paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy and Slovenia.

How to cite: Anselmetti, F. and Buechi, M. and the ICDP-DOVE Team: Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Age, extent and environmental impact of Alpine glaciations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3165, https://doi.org/10.5194/egusphere-egu22-3165, 2022.