Displays

IODP Expedition 358 planned to access and sample the subducting plate boundary at the Nankai Trough, Japan, and commenced on 7 October 2018, and ended on 31 March 2019, marking the ultimate stage of the NanTroSEIZE project. The goal was to drill down to the plate boundary fault, about 5 km below the ocean floor, where >8M earthquakes occur regularly at every 100–150 years. The successful completion would have represented the deepest borehole in the history of scientific ocean drilling and ultimately greatly deepen our understanding about fault mechanics, earthquake inception and tsunami generation processes.

The IODP Expedition 358 intended to access the plate boundary fault zone system through deepening the previously drilled and suspended C0002P hole. The original operational objective of the Exp 358 was to reach a total depth of 7267.5 mbrt (+/- 5200 mbsf) in 4 drilled sections. Previous major riser drilling efforts during the IODP Expeditions 338 and 348 advanced the main riser hole at Site C0002 (Hole C0002F/N/P) to 3058.5 mbsf meters below sea floor (mbsf). Extensive downhole logging data and limited intervals of core were collected during those expeditions.

Due to the nature of the drilling operation and the anticipated challenges ahead, JAMSTEC adopted oil & gas industry drilling standards and performed two detailed Drilling Well on Paper (DWOP) workshops as part of the very rigorous preparatory stage. Great deal of time was spent on selecting new and state-of-the-art drilling/circulating techniques, logging tools, bits and drilling fluid formulation including a new mud sealant additive “FracSeal” to make sure borehole integrity issues can be minimized as much as possible. Drilling stages seen implementation of a novel concept of near real-time geomechanics to continuously monitor and assess borehole integrity.

The challenges born from side-tracking near the bottom of the previously drilled Hole C0002P (2014 Exp. 348), proved greater than the multi-disciplinary teams expected and the overall objectives set for Exp.358 were not achieved. Nevertheless, despite the significant problems seen during several attempts, the hole was deepened 204 m. This is a minor success and it is believed, once away from the highly damaged area of the C0002P hole, drilling can produce a high-integrity hole following excellent communication and recommendations between drilling and scientific teams during complex drilling operations, especially in complex environments such as the Nankai Accretionary Prism.

Despite not achieving the ultimate goal of the expedition, the implemented industry drilling standards, real-time surveillance system, real time geomechanics, improved and strict communication protocols, and integrating both scientific and drilling teams have demonstrated their value and should become standard practice during future IODP/ICDP operations.

How to cite: Wspanialy, A., Toczko, S., Eguchi, N., Maeda, L., Aoike, K., Saruhashi, T., Hirose, T., Ikari, M., Kanagawa, K., Kimura, G., Kinoshita, M., Kitajima, H., Saffer, D., Tobin, H., Yamaguchi, A., and Exp 358 Scientists, I. O. D. P.: A Plate Too Far: Lessons Learned and Insight Gained from scientific and operational achievements during IODP Expedition 358 in the Nankai Trough., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20880, https://doi.org/10.5194/egusphere-egu2020-20880, 2020.

Within the ICDP-Eger drilling project we are developing one of the most modern and comprehensive laboratories at depth worldwide to study the interrelations between the flow of mantle-derived fluids through the crust and their degassing at the surface, the occurrence and characteristics of crustal earthquake swarms, and the relation to the geo-biosphere. The Cheb basin located in the western Eger Rift at the Czech-German border provides an ideal natural laboratory for such a purpose. In October 2016 the ICDP proposal was accepted for complementing two existing shallow monitoring wells with five new, distributed, medium depth (<400 m) drill holes F3 and S1-S4.

The resulting natural laboratory at depth will comprise five drilling sites for studying above mentioned phenomena. The F1-F3 drillings form a unique facility of three wells at one site within an active CO₂ mofette of Hartoušov for continuous recordings of fluid composition and fluid flow rate, as well as for intermittent GeoBio fluid sampling. Drillings S1-S4 are planned for seismological monitoring to reach a new level of high-frequency, near source observations of earthquake swarms and related phenomena such as seismic noise and tremors generated by fluid movements. Instrumentation of the seismic wells S1-S3 will include 8-element geophone chains and a bottom-hole broadband sensor. The borehole sensors will be complemented at S1 by small-scale surface array of approximately 400 m diameter to obtain truly 3D-array configurations. If possible, broadband surface stations and other sensors will be added to each drill location.

So far, we have completed drillings at sites S1, S2 and S3, with depth of 402, 480 and 400 m. The drilling of S4 is planned in 2020 at one of the recently discovered Maars at the Czech-German border region. Drilling F3 was completed in September 2019 at a depth of 239 m. It has reached several over-pressurized, CO2 bearing layers. The three boreholes have been connected by underground tubes system to the nearby field laboratory equipped by flowmeters and mass spectrometers allowing for long time precise monitoring of the degassing process. The S1 borehole (Landwust) will be instrumented in January 2020 by a test geophone chain allowing, along with the DAS fibre-optic cable installed behind the casing, to carry out a VSP measurement.

In our presentation we provide information on the status of drillings, sensor installation and plans for the complete monitoring and data handling concept.

How to cite: Dahm, T., Fischer, T., Woith, H., Hrubcova, P., Vicek, J., Korn, M., Krüger, F., Horalek, J., Vylita, T., and ScienceTeam, I.-E.: ICDP project Drilling the Eger Rift – present status and further plans , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10122, https://doi.org/10.5194/egusphere-egu2020-10122, 2020.

As the world’s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. International Ocean Discovery Program (IODP) Expedition 378 is designed to recover Paleogene sedimentary sections in the South Pacific to reconstruct key changes in oceanic and atmospheric circulation. These cores will provide an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate and as part of a major regional slate of expeditions in the Southern Ocean to fill a critical need for high-latitude climate reconstructions. Appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean.

The drilling strategy included a transect of sites strategically positioned in the South Pacific to recover Paleogene carbonates buried under red clay sequences at present latitudes of 40°–52°S in 4650 – 5075 meters of water depth. Due to technical issues we no longer will be able to reach the deeper sites. Therefore, the focus of Expedition 378 will be now to obtain a continuous sedimentary record of a previously single hole, rotary-drilled, spot-cored, classic Cenozoic high-latitude DSDP Site 277 and provide a crucial, multiple hole, mostly APC-cored, continuous record of the intermediate-depth Subantarctic South Pacific Ocean from the Latest Cretaceous to late Oligocene.

How to cite: Röhl, U., Thomas, D. J., and Childress, L. and the Expedition 378 Science Party: IODP Expedition 378 South Pacific Paleogene Climate: New high-resolution high-latitude Cenozoic Section, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8872, https://doi.org/10.5194/egusphere-egu2020-8872, 2020.

This paper reports on the outcomes of the ICDP drilling into seismogenic zones of M2.0-5.5 earthquakes in South African (SA) gold mines (DSeis; 2017-2018), the follow-up work in 2019, and planned post-drilling activity from 2020 onwards.

In deep SA gold mines, seismogenic zones evolve ahead of thin tabular excavations. Normal faulting prevails because mining enhances the vertical maximum principal stress. At 1km depth at the Cooke 4 mine, we elucidated the evolution of the seismogenic zone with a dense acoustic emission network. In 2017, we successfully recovered both the metasedimentary host rock (mainly quartzite ~2.8 Ga) and samples of the seismogenic zone with well-preserved fracture systems using a triple-tube (BQ 1.5m-long). Subsequent laboratory work investigated critical characteristics of rock-rock friction.

In 2014, an M5.5 earthquake, the largest in deep South African gold mining districts, took place. Dense seismic networks, both on the Earth’s surface and at 2-3 km depth, showed that this event was atypical because it was a sinistral event on an unknown geological structure below the mining horizon in West Rand Group strata (~2.9 Ga). Inversion and back-projection of the ground motion showed complicated but unilateral rupture propagation. The densest population of aftershocks shows a sharp upper cut-off and streaks, both dipping to the south.  Its centroid lies outside the significant main rupture zone. In 2017, we commenced drilling at a site at 2.9km depth in a tension quadrant of the sinistral faulting, several hundreds of meters above the upper fringe of the M5.5 aftershock plane. During 2017-2018, we drilled holes, of a total length of 1.6 km. With a 1.5m NQ triple-tube for the critical section, we could recover the fault materials and the host rock with the seismic fracture system well preserved. Borehole logging and core curation in SA and laboratory work at international organizations, including Kochi Core Center Japan (KCC), followed during 2017-2019. With the geology data mapped on the mining horizons and the legacy seismic reflection data as additional information, the following picture is emerging: (a) transition of the stress regime from normal-faulting to sinistral-faulting; (b) stress localization; (c) heterogeneity in the aftershock distribution as well as the segregation between the main rupture and aftershocks, potentially correlated with significant heterogeneity in mechanical properties; (d) a role of an altered lamprophyre dike; (e) hypersaline brine with salinity even higher than measurements at other deep gold mines, potentially as old as brine found at Kidd Creek mine, Canada; and (f) abiogenic gas and organic carbon.

These data sets allow us to address questions in earthquake and deep-life sciences raised in the ICDP Science Plan (2014-2019). In 2019, the ICDP Executive Committee described DSeis as a ‘successful’ project. To integrate and discuss the outcomes in greater depth and plan additional follow-up work, we are planning a post-drilling workshop in November 2020 or January 2021 at KCC before we return the imported critical section of the core to South Africa.

How to cite: Ogasawara, H., Liebenberg, B., Yabe, Y., Yokoyama, Y., Hirono, T., Nisson, D. M., Onstott, T. C., Kieft, T. L., van Heerden, E., Wiersberg, T., Noda, T., Manzi, M. S. D., Mngadi, S. B., Durrheim, R. J., Yamamaoto, Y., Ito, T., Funato, A., Ziegler, M., Mori, J. J., and Dinske, C. and the The ICDP DSeis team: The seismogenic zones of an M2.0-5.5 earthquakes successfully recovered in deep South African gold mines: the outcomes and the follow-up plan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12094, https://doi.org/10.5194/egusphere-egu2020-12094, 2020.

Although the Arctic Ocean is a major player in the global climate/earth system, this region is one of the last major physiographic provinces on Earth where the short- and long-term geological history is still poorly known. This lack in knowledge is mainly due to the major technological/logistical problems in operating within the permanently ice-covered Arctic region which makes it difficult to retrieve long and undisturbed sediment cores. Continuous central Arctic Ocean sedimentary records, allowing a development of chronologic sequences of climate and environmental change through Cenozoic times and a comparison with global climate records, however, were missing prior to the IODP Expedition 302 (Arctic Ocean Coring Expedition – ACEX), the first scientific drilling in the central Arctic Ocean in 2004. By studying the unique ACEX sequence, a large number of scientific discoveries that describe previously unknown Arctic paleo-environments, were obtained during the last 15 years (for most recent review and references see Stein, 2019a). While these results from ACEX were unprecedented, key questions related to the climate history of the Arctic Ocean remain unanswered, in part because of poor core recovery, and in part because of the possible presence of a major mid-Cenozoic hiatus or interval of starved sedimentation within the ACEX record. Following-up ACEX and its cutting-edge science, a second scientific drilling on Lomonosov Ridge with a focus on the reconstruction of the continuous and complete Cenozoic Arctic Ocean climate history, has been proposed and now scheduled as IODP Expedition 377 "Arctic Ocean Paleoceanography - ArcOP") for late summer/early autumn 2021. Based on new seismic and coring data obtained during Polarstern Expedition PS87 in 2014 (Stein, 2015) and Polarstern Expedition PS115/2 in 2018 (Stein, 2019b), several locations for potential drill sites have been proposed and further optimized. At the primary drill site location, about 230 m of Plio-Pleistocene, 460 m of Miocene, and >200 m of Oligocene-Eocene may be recovered. These new detailed climate records spanning time intervals from the Paleogene Greenhouse world to the Neogene-Quaternary Icehouse world will give new insights into our understanding of the Arctic Ocean within the global climate system and provide an opportunity to test the performance of climate models used to predict future climate change. Within this presentation an update of the primary objectives and the drilling strategy of ArcOP Expedition 377 will be outlined. For further details as well as the drilling proposal we refer to http://www.ecord.org/expedition377/ .

Reference:

Stein, R. (Ed.), 2015. Cruise Report of Expedition PS115/2 of the Research Vessel POLARSTERN to the Arctic Ocean in 2014 (http://epic.awi.de/37728/1/BzPM_0688_2015.pdf).

Stein, R. (Ed.), 2019b. Cruise Report of Expedition PS115/2 of the Research Vessel POLARSTERN to the Arctic Ocean in 2018. (https://epic.awi.de/id/eprint/49226/1/BzPM_0728_2019.pdf ).

Stein, R., 2019a. The late Mesozoic-Cenozoic Arctic Ocean climate and sea ice history: A challenge for past and future scientific ocean drilling. Paleoceanography & Paleoclimatology, ,  https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018PA003433

How to cite: Stein, R., Weigelt, E., Niessen, F., and St. John, K.: Towards a Continuous Cenozoic Arctic Climate Record - A Challenge for IODP Expedition 377 in 2021, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4886, https://doi.org/10.5194/egusphere-egu2020-4886, 2020.

Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply-eroded orogens like the Scandinavian Caledonides allow to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications for a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can help to constrain the origin of this reflectivity. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The core and downhole velocities deviate by up to 2 km/s. However, velocities of mafic rocks are generally in close agreement. Seismic anisotropy increases from about 5 to 26 % at depth, indicating a transition from gneissic to schistose foliation. Differences in the core and downhole velocities are most likely the result of microcracks due to depressurization of the cores. Thus, seismic velocity can help to identify mafic rocks on different scales whereas the velocity signature of other lithologies is obscured in core-derived velocities. Metamorphic foliation on the other hand has a clear expression in seismic anisotropy. To further constrain the effects of mineral composition, microstructure and deformation on the measured seismic anisotropy, we conducted additional microscopic investigations on selected core samples. These analyses using electron-based microscopy and X-ray powder diffractometry indicate that the anisotropy is strongest for mica schists followed by amphibole-rich units. This also emphasizes that seismic velocity and anisotropy are of complementary importance to better distinguish the present lithological units. Our results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.

How to cite: Kästner, F., Pierdominici, S., Elger, J., Berndt, C., Zappone, A., Kück, J., and Schleicher, A. M.: Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: A case study for the COSC-1 borehole, Sweden, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13955, https://doi.org/10.5194/egusphere-egu2020-13955, 2020.

The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major basins of the global ocean, and therefore integrates, forces and responds to global climate variability. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, the Pacific sector of the ACC lacks information on its Cenozoic paleoceanography from deep-sea drilling records.

To advance our knowledge and understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO₂, IODP Expedition 383 recovered sedimentary sequences at: (1) Three sites located in the central South Pacific (Sites U1539, U1540 and U1541); (2) two sites at the Chilean Margin (U1542, U1544); and (3) one site from the hemipelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Age control based on magneto and bio-stratigraphically constrained orbital tuning of physical properties in the Plio-Pleistocene sediments is remarkable, with Sites U1541 and U1543 extending the record back to the late Miocene, and Site U1540 to the earliest Pliocene. Pleistocene sedimentary sequences with high sedimentation rates in the order of 40 cm/kyr were drilled in the Central South Pacific (U1539) and along the Chilean Margin. Taken together, the sites represent a depth transect from ~1100 m at the Chilean margin (U1542) to ~4070 m in the Central South Pacific (U1539), and allow reconstructing changes in the vertical structure of the ACC – a key issue for understanding the role of the Southern Ocean in the global carbon cycle- to be investigated. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic, carbonate, and opal-based proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep ocean variations and their relation to atmosphere and cryosphere changes through stadial-to-interstadial, glacial-to-interglacial and warmer than present time intervals.

How to cite: Lamy, F., Winckler, G., Zarikian, C., and 383 Scientists, E.: Investigating the Dynamics of the Pacific Antarctic Circumpolar Current – Initial Results from International Ocean Discovery Program Expedition 383 (DYNAPACC), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22367, https://doi.org/10.5194/egusphere-egu2020-22367, 2020.

In Early Cretaceous, Shahezi Formation developed in syn-rift stage which belongs to the deep strata of the Songliao Basin, China. Due to the poor outcrop development, there is no previous study or report on the provenance of detrital zircons from Shahezi Formation before. The Songke 2 well is a part of Songliao Basin drilling project which belongs to the International Continental Scientific Drilling Projects (ICDP). The conduct of this scientific drilling is to obtain a nearly complete Cretaceous terrestrial sedimentary record, as determined from basin-filling history. Therefore, this research will focus on the sample from Songke 2 well. This study based on continuous and complete sampling which are unique research materials. What’s more, Songliao Basin is one of the largest continental sedimentary basins in the world, which holds the most important reserves of Chinese oil and natural gas. Consequently, this study is a kind of significance for oil and natural gas prospects of deep strata in Songliao Basin.

Through the detailed description about cores, fan delta facies and lacustrine facies can be identified in this study. Also, the detailed information and sedimentary environment at Early Cretaceous can be clarified. The upper member of Shahezi formation shows the characteristics of fan delta facies intersecting shore-shallow lakes, reflecting the multistage cyclicity changes under the sufficient source supply during the syn-rift stage. In order to define the provenance of the upper member of Shahezi Formation in the north-central area of the Songliao Basin, five sandstone sample (DZ01~05) of the upper member of Shahezi Formation were continuous sampling from Songke 2 well. U-Pb dating was performed on detrital zircons separated from the five sandstone samples. Detrital zircons from DZ01 to DZ05 has dominant ages of 105~140 Ma (268 grains), 155~200 Ma (160 grains), and 220~260 Ma (44 grains). This paper demonstrates that the provenance of the upper member of Shahezi Formation is came from the Central Great Xing’an Range. The depositional period of the Shahezi Formation constraints of maximum sedimentary age and reached to 111-115 Ma. At the same time, the Great Xing’an Range also provides sediments for the western Hailar Basin, which indicates that the Great Xing’an Range uplift and denudation during this period. The closure and collision of the Mongolia-Okhotsk ocean to the north and Pacific Plate subduction beneath the Asian continent to the east were the major tectonic events affecting the tectonic environment of the Great Xing’an Range.

How to cite: An, D.: Early Cretaceous (Aptian) provenance and tectonic response in Songliao Basin, NE China: Evidence from detrital zircon U-Pb ages from the Shahezi Formation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5621, https://doi.org/10.5194/egusphere-egu2020-5621, 2020.

Research on offshore tsunami deposits is scarce and their depositional processes and preservation potential are virtually unexplored. Therefore, the RV Meteor cruise M152 mapped and sampled one coast-parallel and two coast-perpendicular transects at water depths from 65 to 114 m off the Algarve coast (Portugal). This coast was strongly affected by the well-known Lisbon earthquake and tsunami of November 1^st, 1755 AD. Numerous onshore locations have been well documented and studied with historic damage reports and modern scientific investigations of the onshore tsunami deposits. However, very scarce information about the backwash, the water masses flowing back into the sea, exists and their imprint on the shelf is unexplored.

In order to fill this gap, a total of 19 vibracores were recovered during the RV Meteor cruise M152. For tracing the sedimentary imprint of the AD 1755 tsunami and potential predecessors, a multi-proxy analysis was carried out (sedimentology, micropaleontology, inorganic and organic geochemistry, radiocarbon and OSL dating). Within the offshore Holocene stratigraphic record, at least two event layers of likely tsunami backwash origin were identified based on their significantly different properties compared to the background shelf sediments. The uppermost tsunami layer (at a depth of 16-25 cm in most cores) displays an erosional contact at the base with heterogeneous compositional changes; its bounding radiocarbon ages allow a correlation with the AD 1755 Lisbon tsunami. Organic-geochemical markers, such as n-alkanes, polycyclic aromatic hydrocarbons, steroids and fatty acids, show an increased input of terrestrial matter in this offshore AD 1755 event layer.

A surprising discovery was another distinct high-energy deposit, i.e. a potential predecessor to the AD 1755 Lisbon tsunami, at a core depth of about 122-155 cm, which was ¹⁴C-dated to approx. 3700 yrs cal BP. Due to its erosional base and coarse-grained composition (well-sorted medium sand), as well as the increased terrestrial influence (displayed by biomarkers), it can be assumed that this deposit originates from the backwash of a paleo-tsunami.

This multi-proxy approach with sedimentological, micropaleontological, inorganic and organic-geochemical criteria, enabled us to (1) identify of backwash tsunami deposits; (2) establish a recurrence interval; and (3) estimate the hazard potential for the related coastal areas. Results of the M152 cruise demonstrate for the first time that the depositional basins on the Algarve shelf have the potential to reliably archive Holocene tsunami backwash deposits. The low-energy environment of the outer Algarve shelf sets prime conditions for the preservation of tsunami backwash deposits. Thus, these geoarchives offer the possibility to study the mechanisms and hydrodynamics of backwash currents, and to investigate tsunami strata that are not preserved elsewhere.

How to cite: Bellanova, P., Reicherter, K., Costa, P. J. M., Frenken, M., Feist, L., Schwarzbauer, J., Santisteban, J. I., Vött, A., Bosnic, I., Brückner, H., Schüttrumpf, H., Andrade, C., Duarte, J. F., Kuhlmann, J., and M152 scientfic Team, T.: Uncharted archives – imprints of tsunami backwash deposits on the Algarve shelf (Portugal), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7686, https://doi.org/10.5194/egusphere-egu2020-7686, 2020.

A drilling hazard assessment has been completed for a large area of the NW Greenland-Baffin Bay continental shelf. This assessment was in relation to International Ocean Discovery Program (IODP) proposal 909 that aims to drill several sites across the shelf in an attempt to better understand the evolution and variability of the northern Greenland Ice Sheet. The assessment utilised high quality and extensive 3D seismic data that were acquired during recent hydrocarbon exploration interest in the area – a fact that highlights the risk of drilling in a petroleum province and therefore, the importance of this assessment with regards to safety.

Scattered seismic anomalies are observed within the Cenozoic sedimentary succession covering the rift basins of the Melville Bay region. These features, potentially representing the presence of free gas or gas-rich fluids, vary in nature from isolated anomalies, fault flags, stacked fluid flow features and canyons; all of which pose a significant drilling risk and were actively avoided during site selection. In areas above the Melville Bay Ridge – a feature that dominates the structure of this area – free gas is also observed trapped beneath extensive gas hydrate deposits, identified via a spectacularly imaged bottom simulating reflector marking the base of the gas hydrate stability zone. The location of the hydrate deposits, and the free gas beneath, are likely controlled by a complicated migration history, due to large scale rift-related faulting and migration along sandy aquifer horizons. In other areas, gas is interpreted to have reached the shallow subsurface due to secondary leakage from a deeper gas reservoir on the ridge crest.

It is clear that hydrocarbon related hazards within this area are varied and abundant, making it a more challenging location to select sites for an IODP drilling campaign. However, due to the extensive coverage and high resolution (up to 11 m vertical resolution (45 Hz at 2.0 km/s velocity) of the 3D seismic data available, as well as the use of recently acquired ultra-high resolution site survey lines, these features can be accurately imaged and confidently mapped. This allowed for the development of a detailed understanding of the character and distribution of fluids within the shallow subsurface, and the use of this knowledge to select site localities that maximise the potential for drilling to be completed safely and successfully if proposal 909 were to be executed.

How to cite: Cox, D., Newton, A. M. W., Knutz, P. C., and Huuse, M.: Planning a drilling campaign in a petroleum province using high resolution 3D seismic data – IODP proposal 909, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20571, https://doi.org/10.5194/egusphere-egu2020-20571, 2020.

Scientific ocean drilling through the International Ocean Discovery Program (IODP) and its predecessors, has a far-reaching legacy. They have produced vast quantities of marine data, the results of which have revolutionized many geoscience subdisciplines. Meta-analytical studies from these efforts exist for micropaleontology, paleoclimate, and marine sedimentation, and several outstanding resources have curated and made available elements of offshore drilling data (e.g., Neptune), but much of the data remain heterogeneous and dispersed. Each study, therefore, requires reassembling a synthesis of data from numerous sources; a slow, difficult process that limits reproducibility and slows the progress of hypothesis testing and generation. A computer programmatically-accessible repository of scientific ocean drilling data that spans the globe will allow for large-scale marine sedimentary geology and micropaleontologic studies and may help stimulate major advances in these fields.

The eODP project, funded through the NSF’s EarthCube program, seeks to facilitate access to, and visualization of, these large microfossil and stratigraphic datasets. To achieve these goals, eODP will be linking and enhancing the existing database structures of the Paleobiology Database (PBDB) and Macrostrat. This project is targeting shipboard drilling-derived data, but the infrastructure will be put in place to allow the addition of data generated post-cruise. eODP will accomplish the following goals: (1) enable construction of sediment-grounded and flexible age models in an environment that encompasses the deep-sea and outcrops; (2) expand existing lithology and age model construction approaches in this integrated offshore-onshore stratigraphically-focused environment; (3) adapt key microfossil data into the PBDB data model; (4) develop new API-driven web user interfaces for easily discovering and acquiring data; and (5) establish user working groups for community input and feedback. The success of eODP hinges upon interaction, feedback, and contribution of the scientific ocean drilling community, and we invite anyone interested in participating in this project to join the eODP team.

How to cite: Fraass, A., LeVay, L., Sessa, J., and Peters, S.: Extending Ocean Drilling Pursuits [eODP]: Making Scientific Ocean Drilling Data Accessible Through Searchable Databases , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8069, https://doi.org/10.5194/egusphere-egu2020-8069, 2020.

Over the last two decades sea bed drilling technology has proven to provide a valuable complement to the services of classical drill ships. Especially for shallow drillings up to 200 mbsf and when working in remote areas difficult to access, sea bed drill rigs are a cost-effective alternative. Recent developments especially concerning borehole logging techniques add to the capabilities of sea bed drilling technology.

The MARUM-MeBo is a robotic drilling system that is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen (Freudenthal and Wefer, 2013). The drill rig is deployed on the sea bed and remotely controlled from the vessel. It is used for core drilling in soft sediments as well as hard rocks in the deep sea. Especially since an upgrade in 2007/2008 for the use of wireline drilling technique, the first-generation drill rig MARUM-MeBo70 with a drilling capacity of about 70 m was successfully deployed on more than 15 research expeditions. Since 2014 the second-generation drill rig MARUM-MeBo200 with an increased drilling capacity of up to 200 m below sea floor is successfully in operation.

In this presentation we focus on results of three recent drilling campaigns, exemplifying the exploitation of the potential of the sea bed drilling technology:

References:

Freudenthal, T and Wefer, G (2013) Geoscientific Instrumentation, Methods and Data Systems, 2(2). 329-337. doi:10.5194/gi-2-329-2013

Gohl, K, et al. (2017) Geochemistry, Geophysics, Geosystems, 18, 4235–4250. https://doi.org/10.1002/2017GC007081

Klages, JP et al. (in press) Nature, 2019-10-14805B

Riedel, M et al. (2018) Geochemistry, Geophysics, Geosystems, 19, 1165–1177. doi:10.1002/2017GC007288

Riedel, M et al. (in press) Marine and Petroleum Geology, doi.org/10.1016/j.marpetgeo.2019.104192

Wallmann, K et al. (2018) Nature Communications, 9:83, DOI: 10.1038/s41467-017-02550-9

How to cite: Freudenthal, T., Bohrmann, G., Gohl, K., Klages, J. P., Riedel, M., Wallmann, K., and Wefer, G.: More than ten years of successful operation of the MARUM-MeBo sea bed drilling technology: Highlights of recent scientific drilling campaigns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5089, https://doi.org/10.5194/egusphere-egu2020-5089, 2020.

Key archives in environmental and past climate research are buried in soft sediment but investigations are often hampered by the lack of continuous, complete and undisturbed samples. We have developed the new core-drilling instrument Hipercorig to overcome these issues and we have tested this tool successfully on the perialpine Lakes Mondsee and Constance at up to 204 m water depths and down to 64 m core length.

Hipercorig comprises a hydraulically hammered down-the-hole piston coring system capable to reach up to 100 m core length in up to 200 m water depths. The well-proven piston system ensures high-quality intact cores while the hydraulic hammer drive allows penetrating hard-layers such as sand, gravel or tephra. The piston-hammer system, casing string and ground plate is connected via Kevlar ropes to a coring rig and deployment is controlled via underwater cameras. For lake, estuarine and shallow marine projects buoyance and working space is provided through a barge with four anchors and winches. The complete system is consisting of modular elements to be shipped in four 20-foot-containers including two boats and outboard motors. Hipercorig allows for about 10 m rate of penetration per shift and produces 7.5 cm cores in 2 m long core runs.

A first deployment on Lake Mondsee to initially test and modify Hipercorig recovered 64 m sediment core from glacial tills. A follow on shake-down cruise on Lake Constance served as deep-water trial and to sample so far unearthed pre-Holocene strata below about 12 m sediment depth. Coring was performed in summer 2019 in 204 m water depth, 2 km SSW of Hagnau, Germany. The site is located close to the deepest part of this basin with best possible preservation of a continuous and undisturbed depositional record. Two sediment cores of 24 and 20.5 mblf were retrieved and complemented by three 2-m-long surface cores. The uppermost 11 m of sediments consist of Holocene lacustrine clays with increasing intercalations of silt, while late Quaternary glacial sands dominate below 11 m. The piston coring device was modified to allow for penetrating these rigid sand layers, but the sands slowed down core recovery and caused core loss of ~15 cm at the end of each core run but overlapping coring was used to compensate the loss. While samples for microbiology have been taken immediately, core opening, description, and sampling will be performed at Bern University, Switzerland, in October 2019.

Currently Hipercorig receives final upgrades for safety and flexibility so that the whole system will be available from spring 2020 on for scientific coring projects on a non-for-profit base to teams with funded research projects. They will have to raise transport and operations costs as well as a maintenance fee that will serve to sustain the tool. The German Scientific Earth Probing Consortium GESEP will provide an oversight board to prioritize projects and support projects in implementation.

How to cite: Harms, U., Raschke, U., Schwalb, A., and Wittig, V.: Lake Constance sediments recovered using novel piston coring system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13070, https://doi.org/10.5194/egusphere-egu2020-13070, 2020.

Chikyu Shallow Core Program (SCORE) is a short and shallow ocean drilling program arranged by Japan Drilling Earth Science Consortium (J-DESC), Japan. SCORE provides opportunities for scientific ocean drilling test and project which can complete in a short period of time by using the ocean drilling vessel D/V Chikyu except for IODP expedition period. The title of this project is “Enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan: the link between great earthquakes and ridge subduction”. The objective of our program is to investigate the past earthquake occurrence from a continuous sedimentary sequence at a local tectonic basin (i.e., Kanasunose Trough) in Nankai Trough. The target of this drilling program is to find an enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan. Hydraulic Piston Coring System (HPCS) of the ocean drilling vessel (D/V) Chikyu can provide an opportunity to obtain an excellent long and continuous sedimentary record to unravel the earthquake recurrence pattern of this study area.

Expedition 912 was conducted by D/V Chikyu sailing from Shimizu to Sasebo, Japan from 4 January - 15 January 2020. The Leg 1 of Expedition 912 was cored Hole A and B in Site C9035 which are located in 34°05.7’N, 138°08.03’E with 2442 meters of water depth in the Kanasunose Trough, Tokai, Nankai Trough. The Penetration depth at site C9035 is 80.19 meters with HPCS drilled from 5 January to 8 January 2020. The thickness of Hole C9035A sediments was 9.5 m with a recovery of 105%. The thickness of cored sediments was 80.19 meters at Hole C9035B, with a recovery of 104.7%. The shipboard measurements of whole-round core samples involved X-ray CT scan and Physical properties. After splitting, the visual core description (VCD), smear slides, split surface image, Natural Remanent Magnetisation (NRM), penetration strength, and moisture and density (MAD) measurements, and Vane shear test were conducted.

The sedimentary succession is dominated by silty sediments with numerous coarse-grained (coarse silt–very fine sand) layers and some volcanic ash layers and spots. Two lithological units (Unit I and II) can be distinguished on the basis of sedimentary facies. Unit I consists of bioturbated silt and layered coarse silt–very fine sand with massive silt. Three ashes can be founded in Unit I and will provide good age control. Unit II is characterized by matrix-supported gravelly mud–muddy gravel and angular mudstone gravel. After measurements, the extended work of the recurrence intervals of seismo-turbidite in geological time will be built to stimulate the link between great earthquakes and ridge subduction.

How to cite: Hsiung, K.-H., Kanamatsu, T., Ikehara, K., Miura, I., Ashi, J., Kodaira, S., Arai, K., Okutsu, N., and Aoike, K.: Preliminary report on the sedimentary record of SCORE Site C9035 of Tokai, Nankai Trough, southwest Japan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4270, https://doi.org/10.5194/egusphere-egu2020-4270, 2020.

Drilling by the Ocean drilling Program (ODP Legs 104, 152, 163) and geophysical studies have inferred a widespread and strong influence by the Iceland plume on the structure of the ~2500 km long volcanic rifted margins that formed between East Greenland and NW Europe during continental breakupat  ~56-54 Ma. A persistent, but spatially much reduced impact by the plume on crustal structure is evident along the ~250 km Greenland-Iceland-Faeroe ridge (GIFR). Spreading south of the GIFR has remained comparatively stable along the Reykjanes Ridge (RR). By contrast, spreading between the GIFR and northwards to the Jan Mayen Fracture Zone (JMFZ) involved northward rift propagation (~50-25 Ma) away from the Iceland plume and into the East Greenland margin. This was paired with a northward retreat of the initial spreading axis (Aegir ridge (AER)) further to the east. Slivers of the East Greenland continental crust topped by continental plateau basalts extruded during initial breakup were torn off by this northward rift propagation, and form segments of the Jan Mayen microcontinent (JMMC). Rift propagation resulted in the formation of the Iceland Plateau (IP) underlain by anomalously thick and shallow oceanic crust. The striking asymmetry in plate kinematics and crustal structures south and north of Iceland seems associated with a less enriched mantle source feeding the spreading system north of Iceland. This suggests a potentially long-lived north-south asymmetry in the composition and dynamics of the plume that, if confirmed, will favor the existence of distinctly different mantle reservoirs rather than a mixing (entrainment) process followed by a compositional de-convolution process during decompression melting and melt distribution. IODP proposal 976-Pre will address these topics by investigating the temporal and compositional development of the crust of the IP, as well as the transition from rift propagation by the IP rift (IPR) into the present day Kolbeinsey ridge (KR). Drilling will sample 2-3 stages of four IPR propagation stages we have mapped, the transition from the IPR to KR spreading, rifting and timing of transpressive movements along the pseudo-transform zone that linked the propagating IPR to the retreating AER. One drill site hopefully will establish the stratigraphic relationship between the JMMC basalts and the East Greenland plateau basalts. Sediment cover at the drill sites will constrain subsidence history and the paleo-environmental evolution of the high-latitude north-east Atlantic and its connectivity to the global ocean.The proposed drilling addresses long-standing ocean drilling themes of continental breakup, rift propagation, mantle plume reservoirs and structure, and north Atlantic paleoceanography.

How to cite: Larsen, H. C., Blischke, A., and Brandsdóttir, B. and the IODP Proposal 976-Pre working group: Rift propagation north of Iceland: A case of asymmetric plume - rift interaction?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4219, https://doi.org/10.5194/egusphere-egu2020-4219, 2020.

Understanding past variability and forcing mechanisms of the Asian monsoon system is of key importance for better forecasting its behaviour under future global warming scenarios and how this may affect modern societies and economies. So far, knowledge about long-term monsoon variability in mainland Asia is mainly based on proxy records from Chinese speleothems, primarily recording changes of the East Asian Summer Monsoon (EASM). These records have provided evidence for orbital-scale monsoon variability, driven by Northern Hemisphere summer insolation changes, but also for centennial- to millennial-scale reductions in monsoon precipitation. These so-called Weak Monsoon Intervals (WMIs) occurred synchronously to cold intervals in the North Atlantic realm, e.g. during Heinrich Events, pointing at a close hemisphere-scale climatic teleconnection between the North Atlantic and Asia. However, the exact mechanisms that control short-term monsoon variability are still elusive. Moreover, long-term palaeomonsoon proxy records from the core zone of the Indian Summer Monsoon (ISM) are still relatively scarce compared to those from the EASM realm. To identify possible short-term changes in ISM intensity and reconstruct related hydroclimate and vegetation changes on the Indian subcontinent during the interval ~6–74 ka BP, sediments from IODP Site U1446 in the NW Bay of Bengal have been analysed. This site, being located within the reach of the Mahanadi River, is characterized by high riverine input of terrestrial organic matter and thus ideal for high-resolution analyses of pollen content and the stable hydrogen (δD) and carbon (δ¹³C) isotope composition of n-alkanes from terrestrial plant leaf waxes. Here we present preliminary results of δD and δ¹³C analyses on odd-numbered long-chain n-alkanes (n-C₂₇ to n-C₃₃,) extracted from the IODP Site U1446 sediments. These indicate several reductions in ISM precipitation during the last glacial, which occurred parallel to cold events in the North Atlantic realm, e.g. during Heinrich events H1, H2, H4, H5 and H6. In combination with pollen and alkenone-based (U^K’₃₇) sea surface temperature data from the same sediments, we aim at (1) providing a comprehensive and high-resolution reconstruction of past ISM variability and associated vegetation changes on the Indian subcontinent and (2) understanding the trigger mechanisms of centennial- to millennial-scale WMIs, particularly in relation to changes in Indian Ocean oceanography.

How to cite: Lauterbach, S., Andersen, N., Clément, C., Desprat, S., Zorzi, C., Anupama, K., Prasad, S., Oliveira, D., Blanz, T., Thirumalai, K., Clemens, S. C., Martinez, P., and Schneider, R. R.: Indian subcontinent hydroclimate and vegetation changes during the last glacial reconstructed by leaf wax stable isotope and pollen analyses on sediments from IODP Site U1446, NW Bay of Bengal, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19204, https://doi.org/10.5194/egusphere-egu2020-19204, 2020.

Located 300 km off West Iberia in the open NE Atlantic Ocean, the Tore seamount emerges from the 5.5 km surrounding abyssal plains to a summit rim at 2.2 km, which has an elliptical crater-like shape with a central depression 100 km in diameter. The ~5.5 km depth of the Tore internal basin is connected to the surrounding deep ocean basin by a single narrow gateway down to 4.3 km depth. This basin is exceptional because it is 1) a giant sediment-trap for vertical fluxes, with sediments unaffected by deep currents and erosion, containing a record of enhanced biogenic subtropical productivity during deglaciations, which can be examined mechanistically, 2) a natural laboratory to examine carbonate dissolution at 5.5 km water depth constrained by NADW deep ventilation during glacials, and 3) an excellent location to test sediment processes distant from continental margins and understand triggering mechanisms of downslope flows in the open, deep ocean. Not many cores have been recovered in the area at such 5.5 km depth and unite this singular environment. At the larger scale of North Atlantic circulation and productivity, the semi-isolated Tore seamount is a most valuable site to assess crucial scientific hypotheses related to thermohaline circulation, carbon cycling and climate variability. These challenging questions are framed in the IODP Initial Science Plan illuminating Earth´s Past, Present and Future, 2013-2023, theme Climate and Ocean Change.

Our APL applies for drilling one site in the middle of the Tore seamount at 5.5 km depth, to retrieve a complete Quaternary sedimentary sequence (180 m long). This carbonate rich archive will be compared with records available in the Northeast Atlantic and to be recovered during Expedition #771-Full2 (Hodell et al.).

We present results from a 24 long giant Calypso core taken in the APL-site proposed which covers 430 thousand years and 5 glacial-interglacial cycles (Spanish project “TORE5deglaciations”, CTM2017-84113-R, 2018-2020).

How to cite: Lebreiro, S. M., Nave, S., Antón, L., Michel, E., Kissel, C., Waelbroeck, C., McCave, N., Hodell, D., Flores, J.-A., Martinez-Ruiz, F., Martrat, B., Roque, C., Piotrowski, A., Skinner, L., Sierro, F., Terrinha, P., Cornen, G., Reguera, M. I., Lozano-Luz, R., and Bravo, N.: Drilling the Tore seamount- Archive of a natural oceanic sediment trap, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10110, https://doi.org/10.5194/egusphere-egu2020-10110, 2020.

The Mid Pleistocene Transition (MPT) was a global climatic event characterized by a drastic change in the deep thermohaline circulation during the glacial periods that resulted in more intense and longer lasting cold periods and cooler sea-surface temperature (SST). These changes might be linked to the atmospheric pCO₂ reduction which in turn led to colder atmospheric temperatures and the expansion of continental ice sheets. In the mid-latitude North Atlantic, high-resolution records documenting the MPT's impact are still limited. Thus, this study's objective is to contribute to the knowledge by reconstructing circulation changes in the subtropical gyre realm off the southwestern Iberian Margin.  We use planktonic foraminifera faunal data from Integrated Ocean Drilling Program (IODP) Site U1387 (Faro Drift, Gulf of Cadiz) to characterize centennial-scale SST variations during the interval from Marine Isotope Stage (MIS) 18 to MIS 28. The results indicate relative stable SSTs during the interglacial and interstadial periods with temperatures around 20°C during summer and 16°C during winter. During MIS 20, 22, 24, and 25 short-termed extreme cold events were recorded when winter temperatures dropped below 5°C, during late MIS 22 even close to 0°C. They mark the terminal stadial events during deglaciation and were related to increased abundance of polar planktonic foraminifera species N. pachyderma that reached values near to 80%. N. pachyderma values. Percentages of that species between 90 and 50% can be found in the polar regions near the Arctic Front and those between 50 and 5% are indicative of subarctic waters. Whereas the terminal stadial events and the first stadial phase of MIS 22 were marked by incursions of polar surface waters to the southern Iberian margin, abrupt cold events during periods of continental ice shield growth of MIS 19, 21, 25 and 28 were associated with subarctic surface waters. During the MPT, the waters off southern Iberia, therefore, experienced cooling events more extreme than during the last glacial cycle.

How to cite: Mega, A., Salgueiro, E., and Voelker, A. H. L.: Evidence for polar surface-water incursions into the Gulf of Cadiz (SW Iberia) during the Early-to-Mid Pleistocene Transition, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2475, https://doi.org/10.5194/egusphere-egu2020-2475, 2020.

Serpentine seamounts located in the forearc region of a subduction zone setting represent an excellent natural laboratory for studying the geochemical processes acting along convergent plate margins and the associated natural hazards as well as the forearc structure and fault patterns. Active serpentinite mud volcanoes are currently restricted only to the Izu-Bonin-Mariana system, where old (presumably Cretaceous) oceanic lithosphere is subducting in the absence of an accretionary prism.

IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench (Yinazao, Fantangisña and Asùt Tesoru). Most of the material consists of serpentinite mud containing lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific plate. A thin cover of pelagic sediments and volcanic ash deposits underlying the mud volcanos were also recovered. Recycled materials from the subducted slab are found at all three mud volcanoes and consist of metavolcanics rocks, metamorphosed pelagic sediments including cherty limestone as well as fault rocks.

Preliminary investigation of recovered sedimentary clasts from the summit of Fantangisña Seamount revealed that they contain primary calcite veins, whereas the latest veins are composed of aragonite (CaCO₃) and barite (BaSO₄).

Recovered clasts from the flank consist mainly of ultramafic rocks with various degrees of serpentinization. The serpentinite veins consist of lizardite and chrysotile, which suggests rather low temperatures of serpentinization (below 200 °C). Petrological analysis of metabasalt clasts from the same drilling hole shows changes in the mineral composition within the different intervals of the core. The composition of clinopyroxene varies between aegirine-augite and omphacite, but augite is also present. The presence of phengite with Si content of 3.5-3.8 a.p.f.u. indicates minimum pressure of 0.7 GPa at ~250 °C.

Furthermore, providing a detailed characterization of the fluids composition and transport would allow the better constraining of the tectonic and metamorphic history as well as the physical properties of the subducting Pacific Plate. Obtaining data on that point is in progress and will be presented additionally.

How to cite: Kurz, W., Miladinova, I., Del Gaudio, A. V., Piller, W., and Krenn, K.: Serpentinite mud volcanism and exhumation of fore arc- and lower plate material in the Mariana convergent margin system (IODP Expedition 366), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5452, https://doi.org/10.5194/egusphere-egu2020-5452, 2020.

The oceanographic cruise 89 (RRS James Cook) sailed in 2013 off the Iberian margin in support of an IODP proposal centred on IODP Site 1385. JC089 collected a range of hydrographic data and recovered a set of short sediment cores. We focus on 11 of the later, sampling the hydrography of the last c.400 years along a bathymetric gradient (600-4600 m). The stable isotopes (δ¹⁸O & δ¹³C) for: 8 common benthic foraminifer species with varied habitat preferences, the sediment pore-water and the bottom water above the sites were measured. The geochemical data is compared to various sedimentary and micropalaeontological data. The later comprises abundances of the main benthic foraminifera species >212μm, checking for living position of the endo-fauna in Rose-Bengal stained samples and for the abundances of phytodetritus-loving species E.exigua in the >90μm for all the 0-1cm samples. The study of the planktonic foraminifer assemblages along a gradient stretching 170 km offshore confirms the major influence of the upwelling to the East. Except for the epi-benthic species C.wuellestorfi, which records the bottom water δ¹³C at equilibrium, all other species failed to record the δ¹³C of the (pore) water at the depth of their living-position. We find that G.affinis could record the δ¹³C_DIC near equilibrium with the pore-water at a depth of c.-1cm; therefore above its living population peak. This could be explained by vertical migrations through the sediment column at sites where the supply of organic matter is pulsed. The later assumption seems supported by a reverse correlation between high relative abundances of E.exigua and that of the planktonic upwelling indicator species G.bulloides under productivity pulses corresponding to higher Δδ¹³C(epi-G.affinis).

The Δδ¹³C varies from 1.7 to 4.9‰ (n=6) across a decreasing but increasingly pulsed surface productivity gradient further away from the coast. Across this range, G.affinis is observed living at increasing depths in the sediment but always peaks in oxic sediments. The absence of G.affinis from water deeper than 3100 meters prevents Δδ¹³C estimates at deeper water depths. For 6 of the 11 sites where G.affinis was present C.wuellestorfi occurred only twice. The δ¹³C for H.elegans and C.mundulus adjusted by -1.08 and +0.25‰ respectively (this study) were used instead for the shallower sites. Off the Iberian Margin the style of seasonally fluctuating food supply could be the main factor on Δδ¹³C. The implication on future and long-ranging IODP-based palaeoclimatic studies is that the Δδ¹³C could be used to estimate the type of productivity regime back in time. In the one hand the sites mostly influenced by the main upwelling cell exhibit Δδ¹³C < 3‰ & correspond to less than 10% of the time spent in an oligotrophic setting below 0.2mg (chla)/m³. In the other hand Δδ¹³C >3‰ trace offshore rare productive surface filaments in an environment otherwise corresponding to c.90% of the time under oligotrophic surface water. The absence G.affinis (for the range of depths studied) could indicate a record sitting outside either of these productive systems' influence.

How to cite: Mleneck-Vautravers, M. and Hodell, D.: Recent Foraminifers and Stable Isotopes Records on a Bathymetric Transect off Portugal (Cruise JC089) and implications for the Palaeoxygenation proxy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7567, https://doi.org/10.5194/egusphere-egu2020-7567, 2020.

The Corinth Gulf is a semi-closed active rift basin, which alternated between marine and isolated/semi-isolated conditions as sea level fluctuated with respect to basin sills during Quaternary glacial/interglacial cycles. Results from the recent IODP Expedition 381 reveal cyclic variations of 10s-100s of kyr in sedimentation rates and basin paleoenvironment. In this study we investigate the controls on stratigraphic development of the Corinth basin during the last eustatic cycle and the Holocene based on core data from the IODP Expedition 381 Site M0079. We perform a multi-proxy analysis of the upper ~200 mbsf of core covering Marine Isotope Stages (MIS) 1-5 (i.e. last 130 kyr). Our analyses include grain size and micropaleontological (foraminifera) analyses at regular intervals (~0.5 m), Computed Tomography (CT-scanning) of selected u-channels and specific microscopic work (smear slides, SEM) on targeted samples. Our results show pronounced variability in sedimentation patterns during the isolated/semi-isolated phases compared to the marine intervals. Low density, thinly bedded and laminated muds alternating with high density homogenous mud beds and occasionally sandy, organic rich beds prevail during isolated/semi-isolated conditions. In contrast, homogenous and/or highly bioturbated successions characterize the marine sequences. The transitions from marine to isolated/semi-isolated conditions and vise-versa are often associated with authigenic carbonate deposition. Fine grained sediments (sand < 10%) dominate both the marine and the isolated sequences. Nevertheless, sandy turbidites (sand > 10%) are also present and are more often observed in the isolated phases, likely associated with climatic-driven changes in erosional processes onshore. Our analysis reveals short-lived isolated/semi-isolated sub-phases within the lower marine interval corresponding to the MIS5b and MIS5d lowstands. Short marine spikes also interrupt the isolated/semi-isolated conditions of the last glacial period indicating temporary sea level rises within MIS3. Overall, the marine intervals display significant paleoenvironmental differences although they share similar sedimentary patters. In particular, we observe more diverse palaeoceanographic conditions in the MIS5 marine sub-phases compared to the MIS1, especially regarding temperature and eutrophication levels of the water column.  

How to cite: Pechlivanidou, S., Sergiou, S., Geraga, M., Gawthorpe, R., Antoniou, D., Angelopoulou, D., Ford, M., and Fabregas, N.: Controls on stratigraphic variability in a semi-closed rift basin over the Late Quaternary, Gulf of Corinth, Greece, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11898, https://doi.org/10.5194/egusphere-egu2020-11898, 2020.

The continuous wireline core drilling of the COSC-1 borehole (Jämtland, Central Sweden) offered the unique opportunity to combine data and findings from drilling mud gas monitoring, downhole geophysical logging and drill core analysis. The COSC project aims to better understand deep orogenic processes in mountain belts in a major mid-Paleozoic environment in western Scandinavia. The 2.5 km deep fully cored borehole COSC-1 was drilled in 2014 into the lower part of the Seve Nappe Complex, characterized by a thick sequence of high-grade metamorphic rocks. Here, we present results from a combination of drill mud gas monitoring with data from geophysical logging and core analysis to identify and characterize fluid-bearing open fractures during drilling of metamorphic rocks. Geophysical downhole logging is an established technique for extracting information from the underground. Online monitoring of drilling mud gas (OLGA) is also increasingly used in scientific drilling operations, but a combined interpretation of the data sets obtained with these methods has rarely been carried out in the past. Nearly complete gas records were obtained by OLGA with three meter depth resolution from 662 m to 1709 m and six meter resolution from 1709 m to 2490 m depth (COSC-1 total depth: 2496 m) for hydrogen, methane, carbon dioxide and helium by on-line drilling mud gas monitoring. Between 662 m and approx. 1550 m, both He and CH₄ form broad peaks superimposed by several spike-like features. Zones with gas spikes coincide with high resistivity intervals identified by dual laterolog measurements and show fractures in optical drill core scans, borehole televiewer images, and visual core inspection. Therefore, we assume gas inflow through open fractures where deep/shallow resistivity ratios is greater than 1.5 imply the presence of free gas. The correlation between helium and deep/shallow resistivity ratios no longer appears at depths greater than 1550 m, probably because the formation gases are dissolved in formation fluids at higher pressure. 13 gas zones found in the depth interval 662 – 1550 m match with areas of higher resistivity and with open fractures identified by optical core logging. Below 1550 m depth, He drops significantly, whereas CH₄ remains relatively high and H₂ and CO₂ reach maximum values. The high amount of hydrogen and methane at depths below 1616 m, from where friction between the casing and the drill string was reported, imply that these gases are most certainly artificially generated at depths below 1616 m and at least partly of artificial origin at shallower depths. Comparison between OLGA data and resistivity downhole logging data can help to estimate degassing depths: at depths where OLGA identified formation gases, concurrent high resistivity would be diagnostic for free gas, whereas low resistivity would imply gases dissolved in saline formation fluids.

How to cite: Pierdominici, S., Wiersberg, T., Lorenz, H., Almqvist, B., and Klonowska, I. and the COSC Science Team: Integration of drilling mud gas monitoring, downhole geophysical logging and drill core analysis identifies gas inflow zones in borehole COSC-1, Sweden, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3407, https://doi.org/10.5194/egusphere-egu2020-3407, 2020.

Reconstructing the history of continental records covering the glacial-interglacial cycles was the main objective of the ICDP Lake Junín drilling project. Located at 4000 m above sea level, Lake Junín is characterized by a thick sediment package (>125 m) deposited with a sedimentation rate of 14-15 cm/kyr. In fact, the lake predates the maximum extent of glaciation, and is in a geomorphic position to record the waxing and waning of glaciers in the nearby Cordillera. Drilling was performed in 2015 at three sites and a suite of downhole logging measurements were applied. Downhole logging measurements were used to recognize the glacial and interglacial cycles, to reconstruct an age–depth model, to estimate sedimentation rates and to identify electrofacies. Initially, we investigate the consistency of cyclic sediment behavior and see that the interval from ~30-90 m shows a rather stable cyclicity with a wavelength of ~10 m. Natural and spectral gamma ray data were used for cyclostratigraphic analysis, and the astronomical spectral misfit (ASM) method was used to reconstruct the sedimentation rate. The results indicate a sedimentation rate of about 5-20 cm/kyr in the Lake Junín record. Furthermore, the TimeOpt method was applied to test for a fit of precession amplitude with eccentricity; it results in an average sedimentation rate of 15 cm/kyr. Both ASM and TimeOpt are astronomical testing approaches for untuned stratigraphic data in the depth domain that comprehensively evaluate a range of plausible time scales for the deposition history. This method suggests a good fit of the precession amplitude and an eccentricity filter when applying an average sedimentation rate of 14-15 cm/kyr. Based on these information on sedimentation rate, we establish a correlation of the spectral gamma ray data to the LR04 benthic isotope stack. In addition, the downhole logging data were used for cluster analysis to construct a lithological profile, called the electrofacies log.  Three major groups (carbonate-silt, peat and silt) have been identified by spectrum gamma ray, magnetic susceptibility, and p-wave velocity logs. With this method we are able to attribute the lithology in correspondence of core gaps. Finally, the properties of the clusters are analyzed and converted into lithological units according to the lithological information from the visual core description or mineralogical analysis or core material. To achieve this, 68 samples were taken in total from two core runs, in order to compare and characterize the minerals in the lake sediments at different depths. The mineralogical analyses performed by X-ray diffraction (XRD) show quartz, calcite, feldspar and clay minerals. The clay size fraction (< 2 micron) contains illite, smectite and kaolinite in different amounts. Linking the abundance and the lack of clay minerals in core samples with the downhole logging data, a relationship between geological history of the lake and climate change processes can be recognized. Consequently, the different mineralogical composition of the sediments, especially the presence or absence of smectite in the clay bulk, reflects a glacial/interglacial climate cyclicity.

How to cite: Schleicher, A., Pierdominici, S., Zeeden, C., Kück, J., Rodbell, D., and Abbott, M.: Investigating glacial/interglacial cyclicity from downhole logging data and mineralogical composition: an example from the ICDP drilling project Lake Junín, Peru, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3891, https://doi.org/10.5194/egusphere-egu2020-3891, 2020.

Chicxulub crater was formed ~66 Ma ago by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary on the Yucatan carbonate platform in the southern Gulf of Mexico. The crater is the youngest and best preserved of the three large impact basins, with a ~200 km diameter and multi-ring and peak ring morphology. The crater, covered by post-impact carbonate sediments with thickness up to ~1.1 km, has been investigated by geophysical studies and drilling programs. Initial drilling in Yucatan was carried out by the Pemex oil company, followed by the National University UNAM Chicxulub program, the ICDP Yaxcopoil-1 project and the IODP-ICDP Expedition 364 marine drilling. Here, results of combined paleomagnetic, rock magnetic, petrographic and geochemical studies are used to characterize the sequence and constrain the unit’s emplacement and crater formation. We analyze core samples of suevitic breccias and Paleogene carbonates from the Yaxcopoil-1 and Santa Elena boreholes drilled in the southern sector, inside and to the south of the crater rim marked by the ring of cenotes.  Magnetic hysteresis, low-field susceptibility and coercitivity analyses indicate that main carriers are titanomagnetites and magnetite. Mineralogical and magnetic properties indicate effects of hydrothermal alteration, associated with the high temperature system generated by the impact. Higher coercitivity minerals are also observed in some samples. In the carbonate sections, hydrothermal effects as marked by the geochemical logs decrease upwards from the breccia-carbonate contact. Alternating field and thermal demagnetization is used to investigate the magnetization vector composition and isolate the characteristic remanent components. Magnetic polarities defined from the inclination data show a sequence of reverse to normal, which correlate to polarity chrons 29r to 26r, with impact occurring within 29r chron.  The correlations of the magnetostratigraphy and stable isotopes indicate a hiatus at the basal Paleocene section. In Santa Elena cores, d¹³C values range from 1.2 to 3.5%₀ and d¹⁸O values range from -1.4 to -4.8%_0, with variation trends correlating with the marine carbon and oxygen isotope records for the late Maastrichtian and early Paleocene. The positive carbon isotopes indicate high productivity after the K/Pg extinction event, while the oxygen isotope values are more negative reflecting regional and local effects. Silica contents decrease from high in the suevites to low values in carbonates showing higher variability and then increased contents at the Paleocene-Eocene Thermal Maximum (PETM). The geochemical trends correlate in other elements including iron, titanium, potassium and aluminum that record impact-induced hydrothermal effects and possibly changing depositional conditions. Ca shows an opposite trend, with lower values in the upper suevitic breccias, higher values in the Paleocene carbonates and lower values in the PETM.

How to cite: Urrutia-Fucugauchi, J., Perez-Cruz, L., Escobar-Sanchez, E., Velasco-Villarreal, M., and Garcia-Garnica, E.: Rock Magnetic and Magnetostratigraphic Study of Chicxulub Crater Impact Breccias and Post-Impact Carbonates in the Yaxcopoil-1 and Santa Elena Boreholes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19628, https://doi.org/10.5194/egusphere-egu2020-19628, 2020.

Kerguelen Plateau (KP), one of the world’s largest Large Igneous Provinces, is located in a key region in the southern Indian Ocean. Its complex topography has a strong influence on pathways of water masses within the Antarctic Circumpolar Current (ACC) and the Antarctic Bottom Water (AABW). Thick sediment packages deposited on top and around KP are a high-fidelity recorders of significant modifications in pathways and intensities of water masses flowing across the KP during the Cenozoic. Already the previously ODP spot cored sedimentary sequences demonstrated their outstanding potential as a far-field monitor for the evolution of the Antarctic Ice Sheet, for the climate variability in the Warmhouse World of the middle to late Eocene, for changes in ocean circulation, and for migration of the Polar Frontal System. Here we propose to revisited KP and recover a complete, multiple-hole drilled, carbonate rich sedimentary successions from Labuan and Ragatt Basin area by an IODP Expedition. Only high-quality drilled, undisturbed new material will allow studying the interaction of climatic and tectonic changes of the last 66 million years and provide important information on the formation and dynamics of the Antarctic ice sheet due to the unique location of the KP.

How to cite: Westerhold, T. and Uenzelmann-Neben, G.: Kerguelen Plateau Drift Deposits: outstanding high-resolution chronicle of Cenozoic climatic and oceanographic changes in the southern Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3121, https://doi.org/10.5194/egusphere-egu2020-3121, 2020.

Borehole logging data are not yet systematically assessed using cyclostratigraphic methods. In order to obtain a reliable understanding of (long) borehole logging datasets, and especially data from complex settings, a good understanding of the potential and specifics of relevant (time/depth) evolutive methods in cyclostratigraphy are an essential prerequisite. Therefore, we test a suite of evolutive cyclostratigraphic methods using several artificial datasets consisting of modelled Milankovic signals and noise.

Aim of this work is the comparison of different cyclostratigraphic methods for an understanding of which methods are suitable for Quaternary lake records, also for a good understanding of ICDP logging data. Once artificial datasets are discussed, we apply these methods to real data. A discussion of the possible issues and potential of especially uncommon methods gives insight in further potential of cyclostratigraphy.

Lake Ohrid is a tectonic lake located on the border of North Macedonia and Albania. With 1.36 Ma, it is considered Europe’s oldest lake and an important link between Mediterranean climate and African monsoon systems (Wagner et al. 2019). In 2013, an ICDP drilling campaign recovered 2100 m of sediments from four sites (Wagner et al. 2014).

Datasets from geophysical downhole logging provided by the Leibniz Institute for Applied Geophysics are used in a cyclostratigraphic analysis, which provides further insight into the sedimentation history of Lake Ohrid. Here we present initial results from the full succession in this sedimentary archive.

References:

Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., Leng, M. J., Grazhdani, A., Trajanovski, S., Francke, A., Lindhorst, K., Levkov, Z., Cvetkoska, A., Reed, J. M., Zhang, X., Lacey, J. H., Wonik, T., Baumgarten, H., and Vogel, H.: The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid. Sci. Dril., 17, 19–29, doi:10.5194/sd-17-19-2014 (2014).

Wagner, B., Vogel, H., Francke, A. et al.  Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature, 573, 256–260 (2019).

How to cite: Wonik, T., Ulfers, A., Sinnesael, M., Li, M., and Zeeden, C.: Detecting and using Milankovic cycles in borehole logging data: Comparing methods and application to Lake Ohrid, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3671, https://doi.org/10.5194/egusphere-egu2020-3671, 2020.