The Collisional Orogeny in the Scandinavian Caledonides (COSC) multi-disciplinary scientific drilling project characterises the structure and orogenic processes involved in a major collisional mountain belt. Located in western central Sweden, the project drilled its second fully cored borehole, COSC-2, during spring and summer 2020. It extends the COSC composite geological section, which above is composed of outcrops at Åreskutan mountain and the COSC-1 scientific borehole (drilled 2014), through the nappes of the Caledonian Lower Allochthon, the main décollement and the upper kilometre of basement rocks. In summary, the retrieved geological section differs partially from the expected geological section with respect to the depth to the main décollement and the expected rock types. COSC-2 targets include the characterisation of orogen-scale detachments, the impact of orogenesis on the basement below the detachment, and the Early to Lower Ordovician(?) palaeoenvironment on the outer margin of palaeocontinent Baltica. This is complemented by research on heat flow, groundwater flow, gas compositions and characterisation of the microbial community in the present hard rock environment of the relict mountain belt.

COSC-2 successfully, and within budget, recovered a continuous drill core to 2276 m depth. On-site scientific investigations on the drill core by experts were impeded by travel restrictions due to the Covid-19 pandemic. Thus, the core was first completely described in late 2021 at the BGR Core Repository for Scientific Drilling (Berlin Spandau, Germany). After further delay, the sampling party was held in mid-2022.

The entire operations, technical and scientific, were conducted on a 1600 m² drill site. COSC-2 was drilled by the Swedish national research infrastructure for scientific drilling, Riksriggen, with a core recovery close to 100 %. Drilling was performed with water as drilling fluid. Biodegradable polymers were added for drilling in greater depth to reduce friction. Down to 1576 m, HQ triple tube drilling was used (96 mm hole diameter, 61 mm core diameter), followed by NQ triple and double tube drilling to total depth (76 mm hole diameter, 45/48 mm core diameter). Drilling was directly followed by extensive downhole surveying. In autumn 2021, a major surface and borehole seismic survey was conducted, covering approximately an area of 20 km² around the borehole. In 2022, fluid-conducting zones were investigated and fluids sampled with different methods for geochemical (gas and fluid) and microbiological analysis.

The drill site was restored in 2022, leaving a 35 m long and 4 m wide access road to the borehole. This is sufficient for COSC-2 long-term downhole investigations. The borehole is also available for research that is not part of the original COSC project. However, observations during recent downhole investigations suggest that sedimentation with a rate of several tens of meters per year successively is limiting access to the deepest part of the borehole. Scientific results from the COSC project are presented in session TS6.4 "The Caledonian Orogen of the North Atlantic region: insights from geological and geophysical studies".

How to cite: Lorenz, H., Rosberg, J.-E., and Juhlin, C. and the COSC-2 operations team: The COSC-2 scientific drilling project: summary of science, operations, management and legacy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1869, https://doi.org/10.5194/egusphere-egu23-1869, 2023.

We report preliminary results from drill cores and logging from the ICDP Drilling the Ivrea-Verbano zonE (DIVE) project, Hole DT-1b in Ornavasso (Val d’Ossola, northern Italy). Characterized by pronounced geophysical anomalies, the exposed Ivrea-Verbano Zone in the Italian Alps represents an archetypal lower continental crust section. The first phase of DIVE is dedicated to the drilling and the petrological and geophysical characterization of the lowermost continental crust. Specifically, Hole DT-1b was set in the in the hinge zone of the Massone Antiform to explore the pre-Permian lithologies of the lower continental crust. Hole DT-1b was drilled using the diamond double tube continuous wireline coring method, from October 6 to December 10, 2022, and the retrieved rock cores were inspected and classified by the DIVE drilling project science team. Core recovery was effectively 100% throughout the entire drill hole. In total, 578m of the upper part of the lower continental crust in the Ivrea-Verbano Zone were drilled and cored.

Here we summarize on site visual core descriptions and preliminary geophysical logging and microbiological investigations. The cores mostly consist of amphibolites and garnet-bearing metapelites with variable presence of migmatitic structures, and with local high and low temperature shear zones, pegmatitic dikes, and open fractures.

Continuous monitoring of borehole fluids and gases (OLGA and miniRuedi devices, see EGU abstract by Dutoit and coworkers), and a suite of borehole logging measurements (see abstract by Li, Greenwood, Caspari and coworkers) were performed. They match very well the core logs performed on site (magnetic susceptibility and natural gamma radiation). The most prominent, directly observable deformation feature was a high-temperature foliation, with a dip angle between 30 and 60° in the upper part of the hole, becoming increasingly steeper in the deeper part.

Along the entire drill hole fractures and open cracks were observed, some of them filled with precipitates of quartz, carbonates, sulphides and oxides. These fractures are potentially promising hosts for microbial communities and are currently under investigation. Additional samples for microbiological studies were taken every 20m from the drill cores and are currently cultivated for further investigations.

Hole DT-1b provides detailed insights into the compositional, structural and geophysical variation of metasedimentary continental lower crust, including the distribution of sulphides. Relamination of metamorphic pelitic and mafic rocks may produce an important reservoir of sulphur bearing minerals in the lower continental crust. Further results emerging between abstract submission and the conference will be presented.

How to cite: Müntener, O., Hétenyi, G., Greenwood, A., Ziberna, L., Zanetti, A., Pistone, M., and Giovanelli, D. and the DIVE Drilling Project Science Team: Preliminary results from the ICDP - DIVE project: Hole DT-1b (Ornavasso, Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11174, https://doi.org/10.5194/egusphere-egu23-11174, 2023.

Immiscible sulphide liquids, preserved as magmatic sulphide droplets, are believed to strongly control the partitioning behaviour of chalcophile trace elements [1-2]. Hence, the chemical composition of sulphide droplets can be used to understand the fractionation processes of chalcophile elements in magmatic systems that reached sulphide saturation. We carried out LA-ICP-MS analysis of sulphide droplets from gabbros of the lower oceanic crust recovered by deep ocean drilling from mid-ocean ridge spreading centres in the Pacific (ODP147), Indian (ODP176, ODP179, IODP360) and the Atlantic (OPD209 and IODP305) Oceans. For comparison, sulphide droplets from mid-ocean ridge basalts from the East Pacific Rise, Mid-Atlantic Ridge and Southwest Indian Ridge were analysed. Our results show that most gabbros host abundant large magmatic sulphide droplets (mostly above 100 µm up to 1 mm) significantly exceeding those from the related lava units [2-4]. The droplets are commonly associated with or incorporated in olivine or clinopyroxene suggesting an early-stage sulphide saturation but are locally also incorporated in Fe-oxides indicating a later-stage formation during magma cooling [4-5]. The Ni contents of sulphide droplets hosted in gabbros from Hess Deep (Pacific Ocean) are highly variable ranging from ~10 µg/g to weight % levels. Nickel is also strongly controlled by olivine fractionation, and thus can be seen as a parameter indicating whether sulphide saturation was reached before or after the onset of olivine crystallisation. Due to the highly variable Ni contents and in combination with petrographic observations, we suggest that the magma reached early sulphide saturation at Hess Deep, as typically seen in mid-ocean ridge magmatic systems. However, the variable Ni contents in the sulphide droplets indicate that the magma was sulphide-saturated over a longer time span. Alternatively, the magma may frequently switch between being sulphide undersaturated and saturated, due to decreasing pressure during magma ascent accompanied by crystal fractionation at different levels in the crust. Generally, the trace element composition of the sulphide droplets hosted by gabbros from the different drill sites overlap. However, there are significant differences in the compositions of sulphide droplets from lava samples and from associated gabbroic xenoliths [4]. Thus, analysis of droplets from lavas alone provide an incomplete picture of the chalcophile element evolution of the magmatic system. We find no clear differences in sulphide composition with spreading rate or degree of melting as suggested for the silicate melt portion. Instead, the composition of sulphide droplets indicates that fractionation during magma ascent in the crust is the main driver that causes the observed chemical variations, which is part of ongoing investigations.

[1] Wood, B. J. and Kiseeva, E. S. (2015), Earth and Planetary Science Letters, 424, 280-294. [2] Patten, C. et al. (2013), Chemical Geology, 358, 170–188. [3] Peach et al. (1990), Geochimica et Cosmochimica Acta, 12, 3379-3389. [4] Keith, M. et al. (2017), Chemical Geology, 451, 67–77. [5] Jenner, F. E. et al. (2010), Journal of Petrology, 51, 2445-2464.

How to cite: Schäfer, W., Keith, M., Regelous, M., Klemd, R., and Kutzschbach, M.: How scientific ocean drilling helps to decode chalcophile trace element behaviour in mid-ocean ridge magmatic systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12837, https://doi.org/10.5194/egusphere-egu23-12837, 2023.

Shallow slow earthquakes, which last minutes to years, are important indicators of subduction megathrust slip behavior and future seismic and tsunami potential. Subducting plate roughness and seamounts have been proposed to promote slow earthquakes by inducing local geomechanical and hydrogeological anomalies. The Hyuga-Nada region offshore Kyushu, Japan is an outstanding locale for drilling and observatory experiments to investigate these effects. In this region, slow earthquakes are repeatedly observed on and near the subducting Kyushu-Palau-Ridge, KPR, chain of seamounts thus providing excellent opportunities to explore the effects of seamounts on geomechanical/hydrological/thermal properties, and ultimately seismic coupling. Long-term monitoring enabled by a planned permanent network (N-net) will allow subsurface processes during frequent (~1 year) periodical slow earthquakes and ~M7 earthquakes (~20-30 year interval) to be captured with high fidelity. Drilling, logging, and coring will provide key constraints on stress state, hydrological processes, and sediment physical properties in the region above the ridge.  We have originally proposed the drilling and monitoring plan to IODP in 2019 (Nakata et al. 2019). In this presentation, we report the updated proposal plan along with initial processing results of new site survey data acquired with JAMSTEC (Miura et al., 2021, Arai et al., 2021, Ma et al., 2021).

We propose to drill and install observatories at three primary locations in Hyuga-Nada to address two hypotheses: 1) Seamount subduction modulates stress and pore pressure, creates fracture networks and influences the thermal and hydrological state of the margin. 2) The spatiotemporal distribution of slow earthquakes is strongly influenced by seamount subduction through the processes outlined in Hypothesis 1. We will drill three primary distinct sites relative to the seamount, to (1) measure physical properties, and (2) describe deformation by LWD, APCT-3, and core analysis to characterize in-situ stress state, fracture density, heat flow, and pore fluid flow. Spatial variations in the upper plate disruption caused by seamount subduction will be revealed by comparing results from sites in the leading and lateral edges, and top of the currently subducting seamount; and these will constrain geomechanical, hydrological, and thermal models. At two of the sites, we will install a “Fiber-CORK” observatory equipped with conventional pressure and temperature sensors and cutting-edge fiber-optic sensors. One site may be connected to the N-net node for real-time data streaming. The combination will fill a gap in slip durations currently observable in this region with seismic and geodetic instrumentation. Fully characterizing slow earthquakes will reveal the degree to which they accommodate plate motion, and whether strain is accumulated for future earthquakes.

How to cite: Kinoshita, M., Nakata, R., Hashimoto, Y., Hamada, Y., Wallace, L., Sun, T., Araki, E., and Yamashita, Y.: Drilling and monitoring in Hyuga-Nada: Unveiling effects of ridge subduction on slow earthquakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4047, https://doi.org/10.5194/egusphere-egu23-4047, 2023.

Earthquakes are complex natural phenomena that involve multiple spatio-temporal scales. To understand the physical/chemical processes responsible for the faulting that earthquakes occur on, a multidisciplinary approach is highly recommended. Near Fault Observatories (NFOs) aim at providing high-precision and spatio-temporally dense multidisciplinary near fault data, enabling the generation of innovative scientific products.

The Alto Tiberina Near Fault Observatory (TABOO-NFO) is a permanent monitoring infrastructure around the Alto Tiberina Fault (ATF). The ATF is a 60 km long very low-angle normal fault (mean dip 20°) located along a 3 mm/yr extending sector of the Northern Apennines (Central Italy). The presence of repeating earthquakes on the ATF, as well as a steep gradient in crustal velocities measured by GNSS stations, suggest that portions of the ATF are creeping aseismically. Both laboratory and theoretical studies indicate that any given patch of a fault can creep, nucleate slow earthquakes, and host large earthquakes, as also documented in nature for some earthquakes (e.g., Iquique, Tohoku and Parkfield earthquakes). Nonetheless, how a fault patch switches from one mode of slip to another as well as the interaction between creep, slow and regular earthquakes are still poorly documented by near field observation.

TABOO is a state-of-the-art dense network, managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), with mean inter-distance of about 5 km between multidisciplinary sensors, deployed both at surface and within shallow boreholes (<250m). Stations record and transmit in real time via dedicated Wi-Fi technology; then data is stored in standard formats on open access thematic portals and distributed via web services (http://fridge.ingv.it). With STAR, during the Fall of 2021 and Spring of 2022, INGV in collaboration with UNAVCO, drilled six 80-160 m deep boreholes surrounding the creeping portion of the ATF, to deploy Gladwin Tensor strainmeters and short period seismometers. Each “observatory” is also equipped with surface GNSS, meteorological instruments, and additional seismic sensors. The two deepest boreholes host fibre optic cables for temperature and strain. The strainmeter array (STAR) instruments are four-gauge strainmeters, from which we can resolve the horizontal strain matrix and measure deformation on the order of nanostrain, and bridge timescales encompassed neither by GNSS nor by Seismometers. With this new suite of instruments TABOO will enable the collection and calibration of strain records with exquisitely high precision, allowing for a quantitative characterization of ATF creep (~1 mm over <1 km²), enhanced monitoring of microseismicity (below Mc 0.5), and allowing correlation between degassing (CO2, Rn) measurements and subsurface strain.

Such unique near fault data Illuminating the spatiotemporal characteristics of creep on the ATF including possible stress triggering of larger earthquakes by transient creep events, are needed to address key questions of global importance in the seismic hazards and risk assessment community about the physics that allows for both seismic and aseismic slip on a single fault patch.

After presenting the field campaigns, we give an overview of the new data, showing how they enable us to detect new dynamic and static strain features missed by the other in situ instruments.

How to cite: Chiaraluce, L., Mencin, D., Bennett, R., Barchi, M. R., and Bohnhoff, M. and the STAR team: A strainmeter array to unravel the Alto Tiberina fault slip behaviour, Central Italy - ICDP STAR Drilling Project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8462, https://doi.org/10.5194/egusphere-egu23-8462, 2023.

Ostracod shells are small aquatic crustaceans (0.3 - 5 mm) capable of recording climatic and environmental changes at high-resolution in sedimentary archives of modern and ancient lakes. Their stable low-Mg calcite shell mineralogy makes them ideally suited for targeted geochemical analyses. Therefore, ostracods represent the best candidate to develop a new carbonate clumped isotope (∆₄₇) lacustrine paleothermometer that disentangles and quantifies the effects of global climate changes at regional scale. To establish the relationship between ∆₄₇ and the temperature for ostracod shells, three different species were collected in monitored environments at 4°C and 12°C and one was cultivated in the lab at 23°C. Our results show a linear regression between ostracod-∆₄₇ and calcification temperature that is in agreement with previous published calibrations. This implies that ostracods are an equally-good recorder of (paleo)temperatures as other carbonaceous micro- or macrofossils from the marine realm. Moreover, we report the absence of a consistent offset between the species Eucypris virens and Bradleystrandesia fuscata coming from the same environment and precipitated at the same temperature. This observation suggests the absence of a vital effect at the genus and species level. Samples from shallow Lake Trasimeno (Italy) cover the last 50000 years and confirm the ability of the ostracod clumped-isotope thermometer as well as the absence of vital effect in the fossil record. The new paleothermometer identifies warmer/colder and humid/dryer conditions during Greenland Interstadial and Greenland Stadial/Heinrich events respectively.

These findings show that the ostracod-∆₄₇ thermometer has several advantages that makes it an attractive tool for scientific drilling: (i) It is independent of ostracod species and geography. Hence, one can also use endemic species.  (ii) It is applicable throughout geological time, as extinct species can be used. (iii) Temperature reconstructions for all environments where ostracods live are within reach. We emphasize that also high-diversity lacustrine environments are suitable for ∆₄₇ analysis, by mixing shells of different species together. This is of particular importance when working with small samples size from sediment cores.

The establishment of this new lacustrine proxy enables precise paleoclimatic reconstructions from different climate belts. It opens the door to new high-resolution continental paleoclimate and paleoenvironmental reconstructions and therefore has the potential to be a key tool in future lacustrine drilling in the ICDP framework.

How to cite: Marchegiano, M., Peral, M., Venderickx, J., Martens, K., García-Alix, A., Goderis, S., and Claeys, P.: The ostracod clumped-isotope thermometer: A new tool to quantify continental climate change., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11373, https://doi.org/10.5194/egusphere-egu23-11373, 2023.

The mobile Drilling Information System (mDIS) is ICDP’s (Internal Continental Scientific Drilling Program) database management software, initially designed for the acquisition of data gained during a drilling campaign. It is now in use for three years and is by far exceeding its intended application. MDIS has now been installed in core repositories with varying requirements and it is currently been tested for the use as a laboratory data collection application.

The system is based on 25 years of sample and data management at ICDP. It is a database backed web application that is entirely based on open-source code, is platform-independent and has a responsive design. Beyond the basic data registration and management, mDIS provides functionality for QR code label-printing, data export and report generation. Application specific XML export supports International Generic Sample Number (IGSN) registration and data visualization in the “Corelyzer” software (https://cse.umn.edu/csd/corelyzer). Third party software can interface the mDIS through its REST application programming interface (API). Version 3 of the mDIS software features an updated, consistent data model and n:m relations.

Driven by the pandemic, the “expedition mDIS” has mostly been installed as a SaaS (software as a service) variant hosted on a shared ICDP server rather than an offline virtual box application on a personal computer. This solution facilitates training and enhanced support by the ICDP-OSG, it provides continuity by the use of a single project database throughout the project lifespan, and it provides uncomplicated data access to scientists that are currently off-site. Next to the design of further print labels, reports and entry masks for borehole measurements, the most significant extension for the “expedition mDIS” is a digital visual core description allowing for printing a stratigraphic column while simultaneously filling the database. Inspired by a user, our next plan is to develop an add-on for managing sample requests in mDIS.

MDIS has now been implemented in several core repositories (“curation mDIS”), amongst them the Bremen Core Repository (BCR) of the International Ocean Discovery Program (IODP), were curators face up to several thousand samples a week during sample parties. The simultaneous input and processing of large amounts of data lead to new challenges in terms of data handling and database performance. The mDIS has been supplemented with modules to curate and store different sample types, to design and adapt sample series, to add a contact data base and adaptable reports. One of the most important add-ons is the so called “sample-sheet”, which facilitates fast data entry and automated printing of sample labels during large sampling parties.

For more information please visit the ICDP homepage (https://www.icdp-online.org/support/data-samples), the mDIS Documentation website (https://data.icdp-online.org/mdis-docs) or contact us directly. MDIS is open source and as such available for all projects and everybody who is interested.   

How to cite: Heeschen, K., Kunkel, C., Lorenz, H., Bender, V. B., Kuhlmann, H., and Behrends, K.: News on ICDP’s data management system mDIS: experiences, adaptions and extensions after three years of field application and core repository installation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13942, https://doi.org/10.5194/egusphere-egu23-13942, 2023.

The use of µEDXRF elemental mapping provides access to data on relatively large core sections within a reasonable time at high spatial resolution down to 20 µm, enabling to link macroscopic to microscopic information, and providing an objective tool to select areas of interest for more sophisticated data acquisition by EPMA, LA-ICP-MS etc. Textural features can be visualized, that hardly are identified with the naked eye e.g. interstitial silicates in massive chromitites of the Bushveld Complex, South Africa. The application of automated mineralogy provides access to local paragenetic changes and to modal analyses of selected areas. Automated mineralogy based on µEDXRF has to overcome a number of obstacles due to aspects of diffraction, depth of information and grain boundary effects. Tools have been developed to limit these aspects within an acceptable error frame by combining the information of two opposing detectors to reduce the side effects of diffraction. By applying a supervised endmember based classification using the spectral angle mapper algorithm of the ENVI hyperspectral software, phase distribution maps can be produced. Within a well-known system such as the UG-2 chromitite mineral names can be attributed to the identified phases. Exceptions exist for very fine grained secondary phases which might show mixed signals. Well-identified phases can be segmented and grain size, shape and orientation of individual grains can be obtained supported by diffraction signals of single grains. Chemical information can further be extracted for individual minerals, individual grains and bulk area corresponding to the modal mineralogy for any selected area. This offers a new approach to interprete (Verb fehlt?) complex textures by comparing chemical and mineralogical aspects of individual textural pattern. The example of mottled UG-2 chromite shows that the hosting silicates of the chromititebasically orthopyroxene and anorthite-rich plagioclase, but within stringers phlogopite, anorthite-poor plagioclase, potassic feldspar, amphibole, quartz with local enrichment of apatite and sulphides, show differences in grain size and chemistry of the chromite. EPMA investigations on chromite show that Cr/(Cr+Al), Mg/(Mg+Fe), and Cr/Fe is controlled by the chemistry of its hosting oikocryst silicates plagioclase or orthopyroxene. The appearance of late inter-oikocryst phlogopites induces a metasomatic loss of titanium in the chromite. By applying several steps of µEDXRF data reduction and phase masking, these changes in chromite chemistry can be visualized despite of the relatively large spot size of 20 µm for large areas. Using this information the metasomatic impact within a continuously µEDXRF mapped half drill core can be visualized and quantified. 

How to cite: Rammlmair, D., Nikonow, W., and Goldmann, S.: Highlighting the metasomatic impact on mottled UG-2 chromitites from the Bushveld Complex (South Africa)  by large-scale µEDXRF mapping., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16429, https://doi.org/10.5194/egusphere-egu23-16429, 2023.

In 2023, the GEOREAL hydraulic stimulation experiment will be conducted at the KTB deep crustal lab in Windischeschenbach/Germany that originated from the Continental Deep Drilling Program of the Federal Republic of Germany (https://www.gfz-potsdam.de/ktb-tiefenlabor/). The two 4 and 9.1 km deep boreholes were drilled between 1987 and 1994, followed by a long-term experimental program between 1996 and 2005, providing key knowledge on in-situ geomechanical processes and the subsurface at the KTB site. This also led to the foundation of the International Continental Scientific Drilling Program (ICDP) in 1996.

GEOREAL aims at addressing research topics relevant for characterizing the geothermal potential of the metamorphic basement. The two KTB wells provide direct access to a petrothermal fluid reservoir at crustal depth and at temperatures ≥100°C at >3 km depth in the low-permeability rock, typical for large parts of the Earth's crust in Germany. These ambient pressure and temperature conditions are representative for a deep geothermal reservoir and have been extensively studied in the past. GEOREAL builds upon three major injection experiments between 1994 and 2005, during which 150–400 microearthquakes were located in close proximity to the stimulation intervals. The largest induced earthquake of M=1.2 occurred during the phase of highest flow rate. Most of the observed events had M∼0.

The GEOREAL hydraulic stimulation experiment aims at further refining the adaptive reservoir stimulation concept employing near-real-time microseismic monitoring with direct feedback on hydraulic parameters. It will include a series of hydraulic tests at depths ≥3.9 km to investigate the effect of pressure build-up and release, the role of continuous and periodically varying flow rates, the effect of relaxation phases and maximum injection pressure on the spatial propagation of induced earthquakes and the temporal evolution of their magnitudes. This procedure was successfully applied during the 2018 and 2020 geothermal stimulations in Helsinki, Finland. Using a double packer assembly, controlled injection in 15–20 m-long depth intervals, identified through logging will be performed. The goal of GEOREAL is to enhance hydraulic reservoir properties in the KTB pilot hole while avoiding noticeable seismic events. A unique seismic monitoring network will be set up with a 12-level geophone chain in the KTB main hole at only ~300 m distance to the stimulation interval to monitor the fluid injection with high precision. In addition, ≤40 seismometers will be installed surrounding the KTB, including several 45–150 m deep boreholes, and their data transmitted in real-time for rapid evaluation. With this setup, we expect a significantly higher number of locatable microearthquakes than observed during previous injection experiments at the KTB and thus more detailed information on the spatio-temporal propagation of the induced seismicity. A further goal of GEOREAL is to improve existing best practices for technical implementation and to reduce potential risks associated with the technology, thus improving the acceptance of deep geothermal energy in Germany.

How to cite: Boese, C., Dresen, G., Kück, J., Bohnhoff, M., Harms, U., Kamrani-Mehni, S., Zimmermann, G., Sass, I., and Holzförster, F.: GEOREAL: An adaptive stimulation experiment at 3.9 km depth at the KTB deep crustal lab, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12721, https://doi.org/10.5194/egusphere-egu23-12721, 2023.

Driven by the need to understand magmatic systems, to improve volcano monitoring strategy, and to develop next-generation, high-enthalpy, geothermal energy, we introduce the Krafla Magma Testbed (KMT) – located in Northeast Iceland. KMT aims to establish the first magma observatory – an international, open access, scientific platform to advance ductile zone to magma research via drilling and novel sensor systems. This frontier undertaking will enable direct, in situ sampling, instrumentation and manipulation, and monitoring of magma and its interface with solid Earth’s crust, vastly advancing models of high-temperature crustal processes. 

This initiative is enabled by past geothermal drilling at Krafla volcano that was serendipitously intersected and thus determined the exact location of magma for the first time. This unprecedented experience, including safe control of the wells, provides the basis for KMT, which stands to transform modern volcanology and geothermic disciplines. 

KMT will develop a long-term infrastructure (>25 years) for the conduct of interdisciplinary scientific, engineering, technological, and educational activities. The Krafla volcano has the advantage of a long history of geological study, volcano monitoring, and drilling as well as supporting surface facilities combining to produce the safest and most efficient base from which to explore Earth beyond the solidus.  

KMT will be the place to develop (1) our science of hot and molten Earth; (2) new ways of understanding and monitoring volcanoes; (3) our ability to extract and exploit geothermal energy sources; and (4) new technology and materials that function in the most extreme conditions in planetary systems. 

The value of potential gains in fundamental understanding of crustal processes is beyond our possibility to estimate. There is the prospect of an order of magnitude gain in geothermal energy productivity. The need to improve understanding of the source of catastrophic eruptions and to better forecast them is a compelling humanitarian one.

How to cite: Lavallée, Y., Mortensen, A., Papale, P., Eichelberger, J., Sigmundsson, F., Kennedy, B., Villeneuve, M., Jousset, P., Dingwell, D. B., Markusson, S., Eiríksdóttir, V., Pálsson, B., Tester, J., Karlsdóttir, S. N., Midgley, J., Ingolfsson, H. P., and Ludden, J.: Implementing the Krafla Magma Testbed (KMT): linking volcanology and geothermal research for future hazard and energy solutions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7958, https://doi.org/10.5194/egusphere-egu23-7958, 2023.

Lake Bosumtwi was created after a meteorite impact 1.07 Ma ago in an area that is highly susceptible for climate changes due to shifts of the tropical rain belt, as well as variation in dust dynamics. The sedimentary sequence records such changes in the tension field between the North African Monsoon (humid, wet) and the Harmattan (dry and dusty winds from the Sahara) and has been intensively studied. Drilling in 2004, supported by the International Continental Scientific Drilling Program (ICDP), recovered downhole logging data and sediment cores that allow for the analysis of the complete ~300 m lacustrine sequence. Yet, detailed climatic and environmental reconstructions for the record have not been completed, mostly due to the absence of a robust age model beyond 500 ka. In 2022, we obtained core scanning natural gamma ray data of the ~300 m lacustrine sedimentary sequence. Based on this data, we are generating an astronomical age model that can be directly compared to the independently dated sections, but extends farther back in time. Our age model will provide critical chronologic context for the numerous existing and new proxy data that illuminate past changes in climate, environment, and ecosystems. This breakthrough will allow a robust framework to analyse climatic interferences with archaeological findings that might shed new light on habitat availability for our ancestors in tropical Western Africa.

How to cite: Vinnepand, M., Zeeden, C., Noren, A., Kaboth-Bahr, S., Gosling, W., Kück, J., and Wonik, T.: Extending the age model for Lake Bosumtwi (Ghana) to reconstruct West African climate and dust dynamics during the last million years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11822, https://doi.org/10.5194/egusphere-egu23-11822, 2023.

The characteristics of half-precession (HP) cycles (~9,000 - 12,000 years) are still poorly understood, despite their appearance in numerous records. Previous studies on European terrestrial and marine records indicate a connection of the HP-signal to low latitudes. Here, we investigate HP-cycles in equatorial regions to study the assumed origin of this signal.

Spectral analysis, evolutive approaches and correlation techniques are used on records from ODP Sites 662 and 663 to identify the HP-signal in elemental ratios reflecting e.g. terrigenuous input and/or bioproductivity. Filters have been designed to remove the classical orbital cycles (eccentricity, obliquity, precession), in order to isolate the HP-signal and to determine the temporal evolution of its presence and amplitude.

We present first results of a larger project which has the overall objective to characterize the HP-signal across the Mid-Pleistocene Transition (MPT) at Sites 662 and 663. Over the course of the MPT, the ~100 kyr-eccentricity cycles supersede the 41-kyr obliquity as the primary driver of climate forcing. As precession is modulated by eccentricity, a similar relationship may be assumed for HP and eccentricity. Our preliminary analyses show an enhanced HP-signal in the younger, 100-kyr eccentricity world, but also in the late MPT which is partly influenced by the 41-kyr obliquity cycle. Cyclostratigraphic investigations of high-resolution XRF data will provide a clearer insight into the presence, amplitude and role of HP during the MPT and the late Pleistocene.

How to cite: Ulfers, A., Zeeden, C., Kaboth-Bahr, S., Westerhold, T., and Röhl, U.: Cyclostratigraphic investigations with special emphasis on half-precession signals using XRF-data from ODP Site 663 (Eastern Equatorial Atlantic), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17472, https://doi.org/10.5194/egusphere-egu23-17472, 2023.

The age of the ~100 km Manicouagan impact structure (Quebec, Canada) is ~215.5 Ma (1, 2), falling roughly in the middle of the Norian (228-206 Ma) of the Late Triassic, plausibly corresponding to the mid-Norian biotic crisis in the oceans (3) and Adamanian-Revueltian (4) biotic turnover on land. The latter is the largest apparent biotic disruption in the continental Triassic of North America, as documented in the Chinle Formation of the Colorado Plateau and environs in the southwestern USA. Funded by ICDP and NSF (2013-2016), CPCP-1 cored nearly the entire Norian part of the Chinle intersecting what should be the time of the giant impact and biotic transition. Analyses of detrital CA-ID-TIMS U-Pb zircon ages and magnetostratigraphy resulted in two alternative age models for the Chinle in the core (5, 6). Model A emphasized the one-to-one magnetostratigraphic match of polarity zones between the Chinle (5) and the Newark-Hartford Astrochronostratigraphic Polarity Time Scale (N-H APTS) (7) and is consisent with the youngest zircon ages, whereas Model B emphasized the mean of the youngest coherent cluster of ages at a specific level (6). Although both age models agree for the upper stratigraphic core section of the Chinle, they differ dramatically lower down with Model B having three additional accumulation rate segments, one of which is so low as to suggest a hiatus at the Adamanian-Revueltian turnover and Manicouagan impact, similar to a  previous CA-ID-TIMS outcrop study (8). Model A predicts no discernable change in rate or hiatus at the putative event level and only one other accumulation rate segment. Timeseries analysis using Model A reveals significant ~1.8 Myr and 405 kyr cycles in both accumulation rate segments for natural gamma radiation and the elemental XRF ratios, in phase in both segments with the chaotic Mars-Earth and metronomic Venus-Jupiter cycles in the N-H APTS (9). Model B, in contrast, lacks significant cycles at these periods for the lower three accumulation rate segments. Consilience between Model A and the independent astrochronological predictions suggests it is the better model. The discrepancy with Model B is parsimoniously explained by the youngest coherent age clusters tending to be dominated by recycled zircons in the lower part of the core as suggested by LA-ICP-MS data (10). The Adamanian-Revueltian biotic turnover and Manicouagan impact therefore should have a record in the higher accumulation rate part of the Chinle and not be cut out by a hiatus or in a condensed section. Additional coring and denser CA-ID-TIMS ages will be needed to fully test the robustness of this conclusion.

1, Ramezani+ (2005) Geochim, Cosmochim. Acta 69:321. 2, Jaret+ (2018) EPSL 501:78. 3, Onoue+ (2016) Sci. Repts. 6:29609. 4, Parker & Martz (2011) EESTSE 101:231. 5, Kent+ (2019) Geochem. Geophys. Geosyst. 20:4654. 6, Rasmussen+ (2021) GSA Bull. 133:539. 7, Kent+ (2017) Earth-Sci. Rev. 166:153. 8, Ramezani+ (2014) AJS  314:981. 9, Olsen+ (2019) PNAS 116:10664. 10, Gehrels+ (2020) Geochronology 2:257.

How to cite: Olsen, P., Kent, D., Lepre, C., Kinney, S., RoyChowdhury, A., Chang, C., Tibbetts, D., and Bebo, C.: Searching for Manicouagan: astrochronological predictions and tests of alternative age models in the Late Triassic Chinle Formation [Colorado Plateau Coring Project-1 (CPCP-1), Arizona, USA] , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2476, https://doi.org/10.5194/egusphere-egu23-2476, 2023.

Guaymas Basin is a young marginal rift basin in the Gulf of California characterized by active seafloor spreading and rapid sediment deposition, including organic-rich sediments derived from highly productive overlying waters and terrigenous sediments from nearby continental margins. The combination of active seafloor spreading and rapid sedimentation within a narrow basin results in a dynamic environment where linked physical, chemical, and biological processes regulate the cycling of sedimentary carbon and other elements.

During IODP Expedition 385, eight sites were drilled on the flanking regions and in the northern axial graben of Guaymas Basin, recovering organic-rich sediments with sill intrusions. Those cored samples were examined for their microbial cell abundance in a highly sensitive manner by density-gradient cell separation at the super clean room of Kochi Core Center, Japan, followed by direct counting on fluorescence microscopy. Cell abundance in surficial seafloor sediment (~10⁹ cells/cm³) was roughly 1000 times higher than the bottom seawater (~10⁶ cells/cm³) and gradually decreased with increasing depth and temperature. In contrast to the cell abundance profile observed at Nankai Trough (IODP Exp. 370), the gradual decrease of cell abundance was observed up to around 75ºC, and we detected microbial cells even at hot horizons above 100ºC. The existence of smaller size of microbial cells was uniquely found in this region of subseafloor.

We will present the overview of the microbial cell distribution in the Guaymas Basin and discuss its relation to the current and past environmental conditions, e.g., temperature and sill-intrusion, etc.

How to cite: Morono, Y., Teske, A., Bojanova, D., Edgcomb, V., Meyer, N., Schubert, F., Toffin, L., and Galerne, C. and the IODP Expedition 385 Scientists: Microbial cell distribution in the Guaymas Basin subseafloor biosphere, a young marginal rift basin with rich organics and steep temperature gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4098, https://doi.org/10.5194/egusphere-egu23-4098, 2023.

The Neoproterozoic Era (1000 - 541 Ma) is one of the most dramatic in Earth history: metazoans evolved, the supercontinent Rodinia formed and broke apart, the global carbon cycle underwent high-amplitude fluctuations, oxygen concentrations rose and climate experienced at least two episodes of worldwide glaciation. However, the discontinuous and fragmented nature of outcrop-based studies has hindered developing quantitative models of Earth system functioning during that Era. The Geological Research through Integrated Neoproterozoic Drilling (GRIND) project begins to rectify this scientific shortcoming by obtaining 13 cores through the archetype successions that record this environmental and biogeochemical change.

The specific targets are the Ediacaran-Cambrian transition (ECT; c. 560-530 Ma) in south Namibia (Nama Group), strata of west Brazil (Corumbá Group), and South China (Doushantuo, Dengying and equivalent formations). Drilling in Namibia and Brazil is complete, and drilling in China will commence in 2023. The work aims to 1) construct a highly resolved temporal framework that will lead to the development of age models for the ECT; 2) refine the patterns of biotic evolution of organic-walled and mineralised microfossils, metazoans and trace fossils, and identify the links between and test hypotheses about biological evolution and environmental change, and 3) using fresh, unweathered samples, determine the palaeoenvironmental and biogeochemical conditions that led to the rise of oxygen and distinguish cause-and-effect relationships and basin-specific versus global-scale secular trends in geochemical and stable isotope patterns.

We present sedimentological data from the characterised split cores from Namibia and Brazil, which are permanently archived at an in-country repository as well as the Federal Institute for Geosciences and Natural Resources in Germany. All cores will be available for future research, education and national capacity building activities and mark the first step towards creating an on-shore core archive that will match in stature that of the IODP.

How to cite: Rose, C., Prave, T., Baillie, I., Cantine, M., Kasemann, S., Macdonald, F., Mesli, M., Nduutepo, A., Pruss, S., Trindade, R., and Zhu, M.: Grinding through the Ediacaran-Cambrian Transition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9523, https://doi.org/10.5194/egusphere-egu23-9523, 2023.

Units of the up to 3.7 km thick Moodies Group (~3.22 Ga) in the Barberton Greenstone Belt, South Africa and Eswatini, comprise some of the oldest well-preserved sedimentary strata on Earth, deposited within only a few million years in pro-deltaic to alluvial settings, with a dominance of tidal deltas and coastal plains. They consist of widespread quartzose, lithic, tuffaceous and arkosic sandstones, polymict conglomerates, common siltstones and shales, and rare BIFs and jaspilites, all interbedded with rare dacitic air-fall tuffs and several lavas. Moodies strata preserve abundant sedimentary structures and represent a very-high-resolution record of Paleoarchean surface processes. Microbial mats, early diagenetic vadose-alteration zones and tidal rhythmites are locally common. Moodies strata provide a unique opportunity to investigate the conditions under which bacterial life spread and thrived in coastal-zone and terrestrial settings on early Earth.

The ICDP Barberton Archean Surface Environments (BASE) Project drilled November 2021 to July 2022 eight inclined boreholes of 280 to 497 m length each through steeply inclined or overturned Moodies Group strata. The unweathered and continuous core record was complemented by sampling in three several-km-long tunnels and by detailed surface mapping. Two to three rigs operated concurrently, delivering twenty to sixty m of high-quality core daily. This core was processed in a large, publicly accessible hall in downtown Barberton. An exhibition provided background explanations for visitors and related this fundamental-geoscience research project to the geology of the Barberton-Makhonjwa Mountains World Heritage Site. The archive half of the core, nearly 3 km total, remained in South Africa, the working half is curated at the ICDP core repository in Berlin, Germany. We show preliminary cross sections, overall core photographs and representative lithologic descriptions.

How to cite: Heubeck, C. and Beukes, N.: Geologic framework and first results from ICDP BASE drilling in the Moodies Group (~3.22 Ga), Barberton Greenstone Belt, South Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17266, https://doi.org/10.5194/egusphere-egu23-17266, 2023.

Northern Zealandia is a continent submerged for more than 90% under the water of the southwest Pacific Ocean and separated from Australia by the Tasman Sea ocean basin. Its absolute position since its drift form Australia in the Cretaceous is determined by means of global absolute plate motion models, as local paleomagnetic constraints are completely missing. We present new absolute paleolatitudes for northern Zealandia using paleomagnetic data from sediments drilled in International Ocean Discovery Program Sites U1507 and U1511 (Expedition 371^1,2). After correcting for paleomagnetic inclination shallowing, typical of sediments, we derived five paleolatitude estimates that provide a trajectory of northern Zealandia past position from the middle Eocene to early Miocene, spanning geomagnetic polarity chrons C21n to C5Er (~48–18 Ma). Generally, our results support previous works on global absolute plate motion, including a rapid 6° northward migration of northern Zealandia between the early Oligocene–early Miocene. However, paleomagnetic-determined absolute paleolatitude is systematically lower, and this difference is significant in the Bartonian and Priabonian (C18n–C13r). This discrepancy may be explained by some degree of true polar wander, a solid Earth rotation with respect to the spin axis that can be resolved only using paleomagnetic data. These new paleomagnetic dataset anchors past latitudes of Zealandia to Earth’s spin axis, with implications not only for global geodynamics, but for addressing paleoceanographic problems, which generally require precise paleolatitude placement of proxy data³.

Figure 1. Present-day map of northern and southern Zealandia, enveloped respectively by the yellow and orange dashed line. The yellow stars indicate the location of International Ocean Discovery Program Sites U1507 (26.4886°S, 166.5286°E) and U1511 (37.5611°S, 160.3156°E). Solid and dashed white lines indicate active and inactive subduction zones, respectively, with arrows lying on the overriding plate. LHR = Lord Howe Rise, NCT = New Caledonia trough, NR = Norfolk Ridge, RB = Reinga basin.

(¹) Sutherland, R. et al. Proc. Int. Ocean Discov. Progr. 371, 1–33 (2019); (²) Dallanave, E. & Chang, L. Newsletters Stratigr. 53, 365–387 (2020); (³) Dallanave, E. et al. J. Geophys. Res. Solid Earth 127, 1–19 (2022).

How to cite: Dallanave, E., Sutherland, R., Dickens, G., Chang, L., Tema, E., Alegret, L., Agnini, C., Westerhold, T., Newsam, C., Lam, A., Stratford, W., Collot, J., Etienne, S., and von Dobeneck, T.: Middle Eocene to the early Miocene northward migration of northern Zealandia determined from the sedimentary record of IODP Exp. 371 (Tasman Sea), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6477, https://doi.org/10.5194/egusphere-egu23-6477, 2023.

The need for constraining future climate scenarios requires a better understanding of how the cryosphere responded to ocean-climate conditions that were warmer than present. The Greenland shelf margins store thick sedimentary packages that may offer detailed information pertaining to ice-ocean-climate dynamics and Arctic ecosystems. A wealth of seismic data acquired since the early nineties has generated numerous subsurface maps and geomorphic studies of expanded sedimentary archives located proximal to the Greenland Ice Sheet. While paleoclimate reconstructions of ice sheet and ocean dynamics have largely been based on North Atlantic deep-water records, the Greenland continental margin will be the focus of forthcoming International Ocean Discovery Program missions such as Exp. 400, NW Greenland margin. The aim of this presentation is to provide an update of the late Cenozoic marine successions that form key targets for understanding cryospheric behavior during warm climate periods, in particular the Miocene-Pliocene interval characterized by contourite drifts and hemipelagic sequences. The significance for pushing knowledge frontiers on Northern Hemisphere climate evolution and Earth System modelling will be discussed. 

How to cite: Knutz, P., Perez, L., and Nielsen, T.: Late Cenozoic sedimentary systems offshore West Greenland providing new insights to ice-ocean interactions during periods of enhanced climate warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14109, https://doi.org/10.5194/egusphere-egu23-14109, 2023.

The Mariana forearc constitutes the southern sector of the Izu-Bonin-Mariana (IBM) trench-arc system (12° N to 35° N) in the NW Pacific Ocean. It is the only setting where active serpentinite mud volcanism is recorded.

The Mariana forearc hosts several large serpentinite mud volcanoes, among which Fantangisña seamount was cored during International Ocean Discovery Program (IODP) Expedition 366. Lithologies comprise pelagic sediments covering serpentinite mud deposits with ultramafic clasts which derive from the subducting Pacific Plate, forearc crust and mantle. In addition, nannofossil-bearing pelagic sediments and volcanic ash/tephra layers were found at the bottom of the core.

Fantangisña seamount is located in the tropical Pacific region, at low latitudes (16° N) within the latitudinal band of the North Equatorial Current (NEC). The NEC is a warm and nutrient- poor water mass, flowing westward in the tropical Pacific Ocean, driven by trade winds.

In this study, benthic and planktonic foraminifera analyses were performed at Site U1498A, located on the southern flank of Fantangisña serpentinite mud volcano. Most of our analysed interval covers the Early to Late Pleistocene as indicated by previous biostratigraphic investigation on this site. Cluster analyses on Pleistocene planktonic foraminifera resulted in two major clusters based on thermocline-dwelling species (e.g., Globorotalia spp.) to mixed-layer dwellers (e.g., G. ruber, G. rubescens, G. glutinata, Trilobatus spp.) ratio, which infer variations of the depth of the thermocline (DOT) during the Pleistocene. These changes of the DOT can be related to fluctuations in the intensity of the NEC. Our data implies a deep and stable thermocline with an intense NEC during the interval of the Early-Middle Pleistocene Transition (EMPT). In contrast, both thermocline and NEC weakened during the Middle-Late Pleistocene, following the EMPT. Variations in strength of the NEC could be associated with ENSO climate conditions (El Niño/La Niña).

Planktonic foraminifera diversity suggests that the distribution of planktonic assemblages was not affected by the serpentinite mud activity in the area. In addition, our results imply that the preservation of the planktonic tests could be enhanced by rapid burial under the serpentinite mud flows.

High diversity (99 taxa) was recorded for benthic foraminifera before and after the serpentinite mud flow volcanism indicating oligotrophic and well-oxygenated bottom-water conditions. In contrast, benthic species were severely affected by the volcanic activity due to serpentinite mud flows and gas emissions.

How to cite: Del Gaudio, A. V., Piller, W. E., Auer, G., and Kurz, W.: Planktonic and benthic foraminifera assemblages from Fantangisña serpentinite mud volcano in the NW Pacific Ocean during the Pleistocene (IODP Expedition 366), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5797, https://doi.org/10.5194/egusphere-egu23-5797, 2023.

The Iberian margin is a well-known source of rapidly accumulating sediment that preserves a high-fidelity record of millennial climate variability. Previous studies of piston cores and IODP Site U1385 demonstrated that surface, and deep-water climate signals from the region can be correlated precisely to the polar ice cores in both hemispheres and with European terrestrial sequences. The continuity, high sedimentation rates, and fidelity of the climate signals recorded in Iberian margin sediments make this region a prime target for ocean drilling. The primary objective of IODP Expedition 397 was to extend these remarkable paleoclimate records beyond the range of existing piston and IODP cores -- currently limited to the last 1.5 million years. To this end, we recovered a total of 6176.7 m of core at four sites (U1586, U1587, U1385, and U1588) arranged along a bathymetric transect (4691, 3479, 2590 and 1339 mbsl, respectively) to intersect each of the major subsurface water masses of the eastern North Atlantic. The bathymetric transect provides an opportunity to study the history of deep-water circulation, ventilation and carbon storage in the deep eastern North Atlantic and its relationship to changing atmospheric CO₂. Sediments from all sites display strong cyclicity in bulk sediment properties, permitting the development of orbitally-tuned time scales and correlation with classic Mediterranean cyclostratigraphy. We will report on existing results from Site U1385 drilled during Expedition 339, new preliminary results from Expedition 397 sites (including the reoccupation of Site U1385), and discuss the future potential of Iberian margin sediments for providing benchmark paleoclimate records for the late Miocene through Quaternary. 

How to cite: Hodell, D., Fatima, A., and Carlos, Z. and the IODP Expedition 397 Scientists: Benchmark sedimentary records recovered from the Iberian margin during IODP Expedition 397 , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16019, https://doi.org/10.5194/egusphere-egu23-16019, 2023.

Coral reef records related to past higher and/or rising sea levels provide an important baseline for developing projections regarding the response of modern coastal systems to future sea-level rise. Sea-level rise at the end of the current century is expected to range between 5.5 and 10 mm. yr^-1 on average, depending on the various scenarios of  global warming [IPCC, 2019]. The Last Deglaciation (23 to 6 kyr B.P.) is seen as a potential recent analogue of the environmental changes that the Earth may face in the near future as a consequence of ocean thermal expansion and the melting of polar ice sheets. The last deglacial record from Barbados suggests a non-monotonous sea-level rise averaging 10 mm.yr^-1 and punctuated by two ‘meltwater pulses’ (MWP) characterized by several centuries of extremely rapid sea-level rise related to catastrophic ice-sheet collapse [Fairbanks, 1989, Nature, 342, 637; Bard et al., 1990, Nature, 346, 456; Peltier & Fairbanks, 2006, Quat. Sci. Rev., 25, 3322].

IODP Expedition 310 ‘Tahiti Sea Level’ and land drilling on the modern barrier reef of Papeete have provided unparalleled coral reef records encompassing the period covered by the two MWP identified previously in Barbados. Reefs accreted continuously between 16 and 10 kyr B.P. in Tahiti, mostly through aggradational processes, at growth rates averaging 10 mm yr^–1. Changes in the composition of coralgal assemblages coincide with abrupt variations in reef growth rates and characterize the response of the upward-growing reef pile to non-monotonous sea-level rise and coeval environmental changes [Camoin et al., 2012; Geology, 40, 643; Camoin & Webster, 2015; Sedimentology, 62, 401].

While the MWP-1B at approximately 11.3 kyr B.P. in Barbados is absent or very small in Tahiti [Bard et al. 1996; Nature, 382, 241; Bard et al., 2010; Science, 327, 1235; Bard et al., 2016; Paleoceanography, 31], the Tahiti offshore record has provided the opportunity to document the MWP-1A at several drill sites. A sea-level rise of 16±2 m in amplitude has been evidenced between 14.65 and 14.3 kyr B.P., coeval with the Bølling warming [Deschamps et al., 2012, Nature, 483, 559]. The rate of eustatic sea-level rise ranged from 40 to 50 mm.yr^-1 during MWP-1A, implying that this episode corresponds to one of the fastest rises in sea level ever documented in Earth history.

This paper documents in unprecedented detail the reef response to extreme sea-level rise during MWP-1A in Tahiti. It is based on new accurate U-series and ¹⁴C AMS ages of corals and algae and the reappraisal of the environmental significance and paleowater depth interpretation of various coralgal assemblages. The succession in time and space of successive reef assemblages involved in reef accretion during the MWP-1A leads, for the first time, to reconstruct reef accretion patterns during this dramatic period, which is of prime importance to help forecasting coral reef response to future sea-level change.

How to cite: Camoin, G., Bard, E., Deschamps, P., Humblet, M., Braga, J. C., Guilhou, A., Hallmann, N., Weil-Accardo, J., Fagault, Y., and Hamelin, B.: CORAL REEF RESPONSE TO EXTREME SEA-LEVEL CHANGE: THE MELTWATER PULSE 1A (14.65 ka and 14.3 ka BP). IODP EXPEDITION #310 ‘TAHITI SEA LEVEL’, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2139, https://doi.org/10.5194/egusphere-egu23-2139, 2023.

As a contribution towards a regional environmental context of human-climate interactions, the ICDP co-funded Chew Bahir Drilling Project, a part of the HSPDP (Hominin Sites and Paleolakes Drilling Project), recovered ~280-m long cores of sedimentary strata through continental scientific drilling in southern Ethiopia. The fluvio-lacustrine coring locality in the Chew Bahir basin is situated near key archaeological and paleoanthropological sites, such as the Omo-Kibish where the Omo 1 and 2 Homo sapiens fossils were recovered.

Here we present the 620,000-year environmental record from Chew Bahir that provides an extraordinary opportunity to examine the potential influence of climate variability on hominin evolution, cultural innovation and dispersal during the Middle to Late Pleistocene. The near-continuous Chew Bahir record documents 13 environmental episodes that differ in length and character, potentially inducing habitat changes influencing hominin biological and cultural transformation. We infer that long-lasting and relatively stable humid conditions from ~620,000–275,000 years BP (Episodes 1–6) were interrupted by several abrupt and extreme hydroclimatic oscillations. This phase coincided with the appearance of high anatomical diversity in hominin groups. During Episodes 7–9 (~275,000–60,000 years BP), a pronounced pattern of climatic cyclicity was paralleled by the gradual transition from Acheulean to Middle Stone Age technologies, the emergence of H. sapiens in eastern Africa, and a key phase of human social and cultural innovation. Episodes 10–12 (~60,000–10,000 years BP), marked by high-frequency climate oscillations, is contemporaneous with the global dispersal of H. sapiens, facilitated by continued technological innovation and the alignment of humid pulses between eastern Africa and the eastern Mediterranean.

Prospectively, the Chew Bahir record represents a crucial component for the Middle and Late Pleistocene in the ongoing efforts of the scientific community (future and upcoming ICDP-funded projects) to address questions in Africa  across four topical core areas: paleoclimate, paleoenvironment, basin evolution, and modern lake systems.

How to cite: Foerster, V., Asrat, A., Bronk Ramsey, C., Brown, E. T., Deino, A., Grove, M., Hahn, A., Junginger, A., Kaboth-Bahr, S., Lane, C. S., Opitz, S., Noren, A., Roberts, H. M., Tiedemann, R., Vogelsang, R., Vidal, C. M., Cohen, A. S., Lamb, H. F., Schaebitz, F., and Trauth, M. H.: Pleistocene climatic variability in eastern Africa influenced hominin evolution: the 620,000-year climate record from Chew Bahir, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6170, https://doi.org/10.5194/egusphere-egu23-6170, 2023.