SSP1.2

Calderas are major volcanic features with large volcanic and seismic hazards. They also host diverse microbiota, provide heat, energy, mineral and economic benefits. Despite their scientific and socio-economic importance, we still do not completely understand calderas and the interactions between volcanism, tectonism, fluid circulation and the deep biosphere because in-situ and subsurface observations are sparse.

The Okataina Volcanic Centre (OVC) in Aotearoa New Zealand, is one of two active giant calderas of the Taupō Volcanic Zone within the rapidly extending continental intra-arc Taupō Rift. This superb natural laboratory has: 1) numerous past eruptions of varied size and style, 2) documented co-eruptive earthquakes, 3) vigorous hydrothermal manifestations, 4) diverse microbial communities in hot springs but unknown in the subsurface.

We propose to establish a scientific drilling programme at the OVC to address:

• What are the conditions leading to volcanic eruptions; and volcano-tectonic feedbacks in intra-rift calderas?
• What controls fluid circulations in active calderas/rift regions?
• Does subsurface microbial community composition vary with tectonic and/or volcanic activity?

High temperatures complicate drillhole design, restrict data collection and prevent exploration of the biosphere. By targeting the cooler parts of the caldera, this project will use conventional engineering to maximise sampling (drill cores and fluids), downhole logging and establish long-term observatories.

Two preliminary drill targets are suggested: (1) in the centre of the caldera; (2) through the caldera margin. Drill data will provide a comprehensive record of past activity, establishing eruption frequency-magnitude relationships and precursors. Combined with well-known fault rupture history, the relative timing of tectonic and magmatic activity will be untangled. Drill data will unravel the relationships between the groundwater and hydrothermal systems, magma, faults and stress, informing thermo-hydro-mechanical regional caldera models with findings applicable worldwide. Drill cores and a dedicated fluid sampler triggered by nearby earthquakes will reveal the composition, function and potential change of microbial activity in response to rock and fluid variations.

The programme is informed by indigenous Māori, regulatory authorities and emergency managers to ensure scientific, cultural, regulatory and resilience outcomes. The programme will underpin 1) community resilience to volcanic and seismic hazards; 2) sustainable management of groundwater and geothermal resources, and 3) understanding of subsurface microbial diversity, function and geobiological interactions. At these early stages of planning, we invite the scientific community to contribute to the concept of this project in the exceptional OVC settings and strengthen linkages with other ongoing research and scientific drilling programmes.

How to cite: Massiot, C., Miller, C., Stott, M., Villamor, P., Asanuma, H., Boyd, E., Lelli, M., Mcnamara, D. D., Misra, S., Schmitt, D. R., Ventura, G., Wang, P., Adam, L., Bertrand, E., Caratori Tontini, F., Kilgour, G., Milicich, S. D., Nichols, A., and Parisio, F.: INTERACTION: INTeraction between lifE, Rifting And Caldera Tectonics In OkataiNa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1904, https://doi.org/10.5194/egusphere-egu21-1904, 2021.

The Prees-2 fully cored borehole was drilled in November and December 2020 and captures a thick biostratigraphically complete, hemipelagic marine record for the Triassic-Jurassic boundary and for the Hettangian, Sinemurian and lower Pliensbachian stages.  The borehole is sited at the centre of the Prees Jurassic outlier in the Cheshire Basin, Shropshire, England. The overall JET project, funded principally by ICDP, NERC, and DFG, aims to construct a fully integrated age model and timescale for the Early Jurassic combining new data from the Prees core with data generated from the historic Llanbedr (Mochras Farm) borehole in NW Wales.  The new timescale and a wide range of geological data are then being used to reconstruct and understand diverse aspects of the Early Jurassic Earth system, and to provide constraints on astronomical solutions for solar system dynamics over this crucial time interval that links oceanic records of the Cenozoic and later Mesozoic to continental records of the Triassic.  The Prees-2 borehole was drilled to a total depth of 656 m below rig floor, and the Early Jurassic succession comprises mudstone, limestone, and siltstone, which is fossiliferous throughout and includes many biostratigraphically significant ammonite fossils. Diverse trace fossil assemblages are also observed, and lithological cyclicity is apparent through the Jurassic on a scale of about one metre, compatible with interpretations of Milankovitch cyclicity in the precession band based on analysis of Mochras core. Core recovery was largely at 100% and the core quality is excellent. A suite of downhole logs was obtained and ongoing work at the British Geological Survey Core Scanning Facility is generating a high-quality, high-resolution geochemical and geophysical dataset that will provide a fundamental basis for further core-log integration, astrochronology and palaeoenvironmental work.

How to cite: Hesselbo, S. and the JET Science Party: Initial results from coring at Prees, Cheshire Basin, UK, and future plans for the Early Jurassic Earth System and Timescale Project (JET), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12304, https://doi.org/10.5194/egusphere-egu21-12304, 2021.

A series of ICDP deep boreholes of SK1), SK2 and SK3 have been drilled in the Songliao Basin of NE China during 2006 to 2021. The deepest and the most attractive SK2 is with bottom depth of 7108m and super long Continuous coring footage of 4380m. With the long-term working process, we have some special experiences that may be useful to others. The first is that ICDP financial support may cover only a small part of the total cost. But the fishing effect is crucial. That is to say, when we are trying to get financial support, the most important thing above all is generally the reason why do we want to spend the money for. Because of its widely accepted peer review international level program, ICDP funding ,no matter big or small, can always give us strong and convictive argument for the money usage, especially when we are trying to get funded from government organizations and/or companies those are interested in high level research of global aspects. The second is that an ICDP project can be forward in different ways. A step by step procedure is also a very functional way. For example, at the beginning of our ICDP long marching, we got ICDP technical support when we worked on SK1 in 2006. This turned to a key step for the following procedure. Three years later in 2009, we got ICDP funded. The third is that drilling and coring are costly. We may save a lot of money if we can combine ICDP pure research of global aspects with local industry interests. Petroleum companies related to the Songliao Basin kindly provided us all the available data including well-logs, core samples and 3D-seismic data for free. So that, we did not spend any money for the pre-drilling research. And more so, based on these precise data we got very good prediction of the subsurface stratigraphic sections we may meet while drilling, which are very important information for the plans of drilling engineering.

Why we want to drill the deep boreholes of the SK2 coupled with SK1 and SK3.

At first, we hope to obtain a continuous and complete Cretaceous terrestrial coring succession. Situated on the eastern margin of the Eurasian Plate, the Songliao Basin accumulated the most continuous and the highest resolution geological records of Cretaceous terrestrial sedimentary-volcanic successions in the world. The whole Cretaceous sequence is over 10km thick.

Secondly, we hope to establish a high-precision terrestrial stratigraphic framework of the region.

Thirdly, we hope to study the Cretaceous conditions concerning paleo-environment of the lakes in the Songliao Basin and adjacent areas. At last, research on paleoclimatic aspects in northeastern Asia based on the collected precise lake deposits. And then, According to the knowledge acquired from the global warming process in the Cretaceous in NE Asia, especially during the stages of intense fossil fuel accumulation episodes, we may have the opportunity try to find some similarities to the global warming trend that human being is facing now.

How to cite: Wang, P., Zhu, Y., Gao, Y., Wan, X., Ren, Y., Wang, S., Qu, X., Meng, Q., Huang, Y., Huang, Q., Liu, H., and Wang, C.: A successfully finished ICDP deep borehole of 7108m (SK2)in the Cretaceous Songliao Basin of Northeast China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3930, https://doi.org/10.5194/egusphere-egu21-3930, 2021.

In the Songliao Basin, the existence of lower Mesozoic strata remains a debatable issue. Previous studies indicated the absence of Triassic to Lower and Middle Jurassic strata in northeastern China because of uplift and erosion events associated with the return of geo-synclinal folds and orogenic movement during the Late Permian–Early Jurassic. To date, geochronological studies of intrusive and metamorphic rocks in the basement of the Songliao Basin have also confirmed Carboniferous, Permian, and Late Jurassic ages for the basement formations in general. In the International Continental Scientific Drilling Project (ICDP) in the Songliao Basin, radiometric dating has been carried out for the entire drilling core of the SK-2 east borehole. As a result, we have discovered Triassic volcanic-sedimentary strata in the basement of the Songliao Basin. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology was used in this research. Errors in individual analyses by LA-ICP-MS are given at the 1σ level, whereas errors in pooled ages are given at the 95% (2σ) confidence level. Triassic volcanic-sedimentary strata revealed by the SK-2 east borehole consist of andesitic volcanic breccias at the bottom; andesites, sandstones, and conglomerates in the middle; and andesites at the top. The total thickness of these strata is over 500 m. The formation age of the andesite at the depth of 6,031.9 m is 242.4 ± 2.1 Ma (MSWD = 0.06, n = 7). The youngest peak age of the sandstone at the depth of 6,286.2 m is 242.2 Ma. The formation age of the andesite at the depth of 6,286.2 m is 242.6 ± 1.5 Ma (MSWD = 1.02, n = 18). This study demonstrates that in the Songliao Basin, there are not only Carboniferous and Permian strata, but also a Triassic volcanic-sedimentary succession in the basement of the basin. The SK-2 drilling core reveals that this volcanic-sedimentary sequence has great thickness. These Triassic volcanic-sedimentary strata provide new clues for the study of the origin and development of the Songliao Basin. As both volcanic and sedimentary rocks can be oil and gas reservoirs, this discovery also provides a new target for oil and gas exploration deep in the Songliao Basin.

How to cite: Yin, Y., Wang, P., Gao, Y., and Liu, H.: Triassic volcanic-sedimentary strata in the basement of Songliao Basin, discovered by International Continental Scientific Drilling Borehole, SK-2, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1874, https://doi.org/10.5194/egusphere-egu21-1874, 2021.

COSC investigations and drilling activities are focused in the Åre-Mörsil area (Sweden) of central Scandinavia. COSC-2 was drilled with nearly 100% core recovery in 2020 to 2.276 km depth with drilling ongoing from mid-April to early August. Drilling targets for COSC-2 included (1) the highly conductive Alum shale, (2) the Caledonian décollement, the major detachment that separates the Caledonian allochthons from the autochthonous basement of the Fennoscandian Shield, and (3) the strong seismic reflectors in the Precambrian basement.

Combined seismic, magnetotelluric (MT) and magnetic data were used to site the COSC-2 borehole about 20 km east-southeast of COSC-1. Based on these data it was predicted that the uppermost, tectonic occurrence of Cambrian Alum shale would be penetrated at about 800 m, the main décollement in Alum shale at its stratigraphic level at about 1200 m and the uppermost high amplitude basement reflector at about 1600 m. Paleozoic turbidites and greywackes were expected to be drilled down to 800 m depth. Below this depth, Ordovician limestone and shale with imbricates of Alum shale were interpreted to be present. Directly below the main décollement, magnetite rich Precambrian basement was expected to be encountered with a composition similar to that of magnetic granitic rocks found east of the Caledonian Front. The actual depths of the main contacts turned out to agree very well with the predictions based on the geophysical data. However, the geology below the uppermost occurrence of Alum shale is quite different from the expected model. Alum shale was only clearly encountered as a highly deformed, about 30 m thick unit, starting at about 790 m. Between about 820 and 1200 m, preliminary interpretations are that the rocks mainly consist of Neo-Proterozoic to Early Cambrian tuffs. Further below, Precambrian porphyries are present. The high amplitude reflections within the Precambrian sequence appear to be generated by dolerite sheets with the uppermost top penetrated at about 1600 m. Several deformed sheets of dolerite may be present down to about 1930 m. Below this depth the rocks are again porphyries.

A preliminary conclusion concerning the tectonic model is that the main décollement is at about 800 m and not at 1200 m. Also the thickness of the lowermost Cambrian/uppermost Neoproterozoic sediments on top of the basement is much greater than expected (hundreds of meters instead of tens of meters) and likely to have been thickened tectonically. Detailed studies are required to assess the actual importance of the “main décollement” and the degree, type and age of deformation in its footwall. We can also conclude that the Precambrian basement is very similar to the Dala porphyries succession that are typically present farther south.

An extensive set of downhole logging data was acquired directly after drilling. Borehole seismic measurements in 2021 will help to define and correlate seismic boundaries with lithology and structures in the core. Unfortunately, work for describing the geology of the drill core in detail is still on hold due to Covid-19.

How to cite: Juhlin, C., Almqvist, B., Anderson, M., Dopson, M., Klonowska, I., Lehnert, O., Lescoutre, R., Lorenz, H., Pascal, C., Piazolo, S., Roberts, N., Rosberg, J.-E., and Tsang, C.-F.: Collisional Orogeny in the Scandinavian Caledonides (COSC): Some preliminary results from drilling of the 2.276 km deep COSC-2 borehole, central Sweden, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-538, https://doi.org/10.5194/egusphere-egu21-538, 2021.

Continental collision causes deformation in the crust along shear zones. However, the physical and chemical conditions at which these zones operate and the deformation processes that enable up to hundreds of km of tectonic transport are still unclear because of the depth at which they occur and the challenges in imaging them. Ancient exhumed collision zones allow us to investigate these processes much better, for example at the COSC-1 borehole in the central Scandinavian Caledonides. This study combines data from the COSC-1 borehole, such as downhole logging and zero-offset vertical seismic profile data, with 2D and 3D seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. This is one of the few studies that shows that core-log-seismic integration in metamorphic rocks allows to identify the spatial distribution of major lithological units, even though the methodology was originally developed for sedimentary basins in the hydrocarbon industry. Especially gamma ray logs in combination with density data are powerful tools to distinguish between mafic and felsic lithologies in log-core correlation. Reflections in the Seve Nappe Complex are not as distinct as in greater depths but continuous, and our results indicate that they are primarily caused by compositional rather than textural changes. Several of the reflections can be linked to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. It appears that in spite of the metamorphic overprint around 417+/-9 Ma, the original configuration of the volcanic passive margin is partly preserved in the Seve Nappe Complex and that it outlasted continent-continent collision, including the nappe emplacement. Thus, an integration of borehole and three-dimensional geophysical data can image lithological changes that can then be extrapolated in three dimensions to arrive at a better understanding of the composition and geometry at mid-crustal levels. Furthermore, our results suggest that ductile-deformed middle crustal reflectivity is primarily a function of pre-orogenic lithological variations which has to be considered when deciphering mountain building processes.

How to cite: Elger, J., Berndt, C., Kästner, F., Pierdominici, S., Kück, J., Almqvist, B. S. G., Juhlin, C., and Lorenz, H.: Core-log-seismic integration in metamorphic rocks at the ICDP drilling project COSC-1, Sweden, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2321, https://doi.org/10.5194/egusphere-egu21-2321, 2021.

While the mechanical properties of plate boundaries are relatively well known and characterized by earthquake occurrence, intraplate regions are still largely “terra incognita”, especially in cratonic shields where only seldom and very few data related to the state of the stress field are available. The only way to detect such data and understand the geological and physical processes responsible for the present stress field in an intraplate area is to carry out in-situ measurements of stress-induced deformation in a borehole over time. We had a unique and extraordinary opportunity to measure and investigate the time-dependent deformation in an aseismic area directly in-situ inside the 2500 m Outokumpu open borehole in eastern Finland. The stress data acquired in 2006 and 2011 have been analysed and show that a slow but continued deformation of the upper part of the Earth‘s crust, albeit unexpected, is still ongoing. The continuous formation and development of stress-induced borehole enlargements in a tectonically very stable and almost aseismic area is unforeseen and raises questions of global importance. For this, two complementary approaches were conducted: identification of breakout zones and rock physics measurements on selected drill cores. We compared the two datasets to study the changes of breakout geometry and to quantify the growth of the breakouts in this time span from differences in width, length and depth. For the second method, UCS experiments were conducted providing unconfined compressive strength on specimens collected from above, middle and below breakout zones, and rough estimates of the static Young’s modulus based on the initial length and axial travel of the load frame. The sample height-diameter (H:D) ratio of available drill cores was less than required in testing standards (ASTM D7012, 2014, ISRM 1999). The relatively small grain size of drill cores allowed drilling of smaller-diameter subcores that in most cases fulfilled or exceeded the minimum H:D ratio (1.7<H:D<2.3). We realized that also along the same lithology some zones are affected by enlargements and other remain undamaged. Therefore, we performed the geomechanical analyses on specimens from the same lithology but not affected by failures. Fifty-one uniaxial compressive tests were conducted on specimens belonging to four main rock types at different depths: biotite gneiss, diopside tremolite skarn, micaschist and serpentinite. Results from geomechanical test show UCS values range from 27 to 245 MPa with an average of 102 MPa and a standard deviation of 42, while the elastic Youngs modulus range from 3 to 20 GPa with an average of 7.3 GPa and a standard deviation of 2.8. Most samples collected within breakout zones have UCS values from 40 to 170 MPa and H:D ratio from 1.8 to 2.0, less that required by the standards. The samples outside of the breakout zones show UCS values from 27 to 186 MPa, and H:D ratio from 1.7 to 2.3. The hypothesis for testing was that borehole breakouts were formed in weaker rocks. Our results does not confirm this hypothesis, but the observed time-dependent deformation in Outokumpu borehole is interesting and calls for further studies.

How to cite: Pierdominici, S. and Ask, M.: Rock strength and time dependent deformation of borehole breakouts in the ICDP Outokumpu deep borehole, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6259, https://doi.org/10.5194/egusphere-egu21-6259, 2021.

Lake Ohrid is located on the Balkan Peninsula between Albania and North Macedonia. It is considered Europe’s oldest lake and thus is a valuable archive for studies that focus on the change of local (hydro-)climate during the last 1.36 million years (e.g., Francke et al. 2016; Wagner et al. 2019). During an International Continental Scientific Drilling Program (ICDP) campaign in 2013, geophysical downhole logging by the Leibniz Institute for Applied Geophysics acquired continuous datasets of physical properties. Additionally, 2100 m of sediment core was obtained from different sites, the deepest with a length of 570 m (Wagner et al. 2014).

Investigations of half-precession (HP) cycles (~9,000 – 12,000 years) have been given only a small role or have been completely neglected in previous cyclostratographic studies. In this study we focus on HP signals in Lake Ohrid and investigate the temporal variability of this signal over the last one million of years. Next to a connection of HP cycles to interglacials, we see a more pronounced correlation of the HP signal to natural gamma radiation logs in the younger part of the record.

We relate the results from Lake Ohrid to a variety of proxy records from the European mainland and marine sediment cores from the Atlantic and the Mediterranean. Certain patterns, such as the increased visibility of the HP signal in interglacials, occur in most records, but differences, like variations in the amplitude modulation of the filtered HP signal, need to be investiagted in more detail. Nevertheless, the HP cycles are contained in all of the investigated sites, although the records are influenced by different climatic systems. This illustrates that HP signals cannot be connected to a certain climatic system, but can occur simultaneously in records with different proxy signal origins.

HP cycles are a relevant part of natural climate variability - also in Europe - and allow a more detailed investiagtion of sedimentary systems.

References:

Francke, A., Wagner, B., Just, J., Leicher, N., Gromig, R., Baumgarten, H., … & Giacco, B. (2016). Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 637 ka and the present, Biogeosciences , 13, 1179–1196.

Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., …. & Vogel, H. (2014). The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid, Sci. Drill. , 17, 19-29.

Wagner, B., Vogel, H., Francke, A., Friedrich, T., Donders, T., Lacey, J. H., … & Zhang, X. . (2019). Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years, Nature , 573(7773), 256-260.

How to cite: Ulfers, A., Zeeden, C., Voigt, S., and Wonik, T.: Half-precession signals in Lake Ohrid and their spatial and temporal connection to proxy records in the European realm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5321, https://doi.org/10.5194/egusphere-egu21-5321, 2021.

The West Antarctic Ice Sheet (WAIS) is thought to be highly sensitive to climatic and oceanographic changes. Modelling infers that the WAIS likely had a very dynamic history throughout the Neogene to the present. A complete collapse of the WAIS would result in a global sea level rise of 3.3 to 4.3 m, yet there is large uncertainty on predicting its future behavior and its contribution to sea level rise. Geological constraints on the past behavior of the WAIS are relatively sparse and mainly based on records from the Ross Sea sector. In particular, records of time intervals with climatic conditions similar to those expected for the near and distant future, such as the Pliocene, are needed. Deglaciation of the WAIS in the Amundsen Sea sector is hypothesized to have triggered WAIS collapses during past warm times. Drill records from the International Ocean Discovery Program (IODP) Expedition 379 provide continuous late Miocene to Pleistocene sediment sequences from a drift on the continental rise, allowing the assessment of sedimentation processes from cold and warm times. In particular Site U1532 recovered an expanded sequence of Pliocene lithofacies with an excellent paleomagnetic record allowing for very high-resolution, sub-orbital scale climate change studies of the previously sparsely sampled eastern Pacific sector of the West Antarctic margin. At both Sites U1532 and U1533, sediments characterized by high microfossil content and high abundance of ice-rafted debris alternate with laminated terrigenous muds and are interpreted to result from cyclic deposition under interglacial and glacial conditions, respectively. Deep-sea channels likely mark the pathways of terrigenous detritus that was transported downslope from the Amundsen Sea shelf via turbidity currents or other gravitational transport processes predominantly during glacial periods. The association of lithological facies predominantly reflects an interplay of these downslope and contouritic sediment transport processes as well as phases of increased pelagic and hemipelagic sediment input. Correlation of the seismic stratigraphy at the drill sites on the rise with that of the continental shelf of the Amundsen Sea Embayment allowed us to identify massive prograding sequences that expanded the outer shelf seaward by about 80 km by frequent advances of grounded ice across the shelf mainly during Pliocene times. The preservation of buried grounding zone wedges visible in seismic profiles from the shelf is explained by (hemi)pelagic sedimentation during prolonged periods of ice retreat. This can be correlated with an extended warm middle Pliocene period chronologically constrained by the drill records. The contrast between sediments deposited under cold and warm climate conditions indicates that this WAIS sector was highly dynamic in the Pliocene.

How to cite: Gohl, K., Gille-Petzoldt, J., Uenzelmann-Neben, G., Lamb, R., Klages, J., Wellner, J., Passchier, S., Hillenbrand, C.-D., Bohaty, S., Thomas, F., and Leitchenkov, G. and the IODP Expedition 379 Scientists: IODP Expedition 379: Late Miocene to Pleistocene shelf to rise processes in the Amundsen Sea, West Antarctica, from seismic correlation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14232, https://doi.org/10.5194/egusphere-egu21-14232, 2021.

The new sedimentary record from the Gulf of Corinth (south Greece), retrieved within the IODP Exp. 381: Corinth Active Rift Development, is a new archive registering environmental and climatic variability continuously over the last one million years. The Gulf of Corinth, strategically located at the southernmost tip of the Balkan Peninsula, is a semi-enclosed basin that is sensitive to climate forcing and sea level fluctuations. The Gulf was repeatedly isolated from the Mediterranean Sea during glacial/low-stand intervals, resulting in the amplification of paleoenvironmental gradients (McNeill et al., 2019).

The “Quaternary Environmental Changes in the Corinth Rift Area: the IODP 381 palaeovegetation record (QECCoRA)” project aims to analyse how climate variability affected the development of local vegetation and marine ecosystems in response to glacial/interglacial cycles, using palynological analysis (terrestrial and aquatic palynomorphs). The main goals are: a) to study the glacial-interglacial vegetation history in the southernmost Balkan tree refugium at a millennial scale b) to constrain the timing of Quaternary extinctions of relict tree taxa, and c) to decipher the alternation between marine and isolated intervals and its impact on aquatic ecosystems and the depositional environment using the aquatic palynomorph record.

The first results of the microscopic analysis show significant shifts of the vegetation composition in response to climate variability, nevertheless the fluctuation in vegetation cover appears less pronounced. Dinoflagellate cysts show distinct alternations between marine and brackish conditions revealing changes in surface water salinity, productivity, and temperature. Ongoing palynological analysis will produce a skeleton paleoenvironmental record that will contribute to further analyses carried out within the IODP Exp. 381 Science team.

The QECCoRA project is supported by the Hellenic Foundation of Research and Innovation (H.F.R.I., Project Number: 1026)

Reference

McNeill LC, Shillington DJ, Carter GDO, Everest J, Gawthorpe R, Miller C, Phillips M, Collier R, Cvetkoska A, De Gelder G, Diz Ferreiro P, Doan M-L, Ford M, Geraga M, Gillespie J, Hemelsdael R, Herrero-Bervera E, Ismaiel M, Janikian L, Kouli K, Le Ber E, Li S, Maffione M, Mahoney C, Machlus M, Michas G, Nixon C, Oflaz SA, Omale A, Panagiotopoulos K, Pechlivanidou S, Sauer S, Seguin J, Sergiou S, Zhakarova N, Green S, High-resolution record reveals climate-driven environmental and sedimentary changes in an active rift, Scientific Reports, 9:3116, 2019, https://doi.org/10.1038/s41598-019-40022-w

How to cite: Fatourou, E., Kafetzidou, A., Panagiotopoulos, K., Marret, F., Papadopoulou, S., Kouli, K., and 381 Science Team, T. E.: Quaternary Environmental Changes in the Corinth Rift Area: the IODP 381 Palynological Record, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11360, https://doi.org/10.5194/egusphere-egu21-11360, 2021.

High-resolution 2D multichannel seismic data collected by the Alfred Wegener Institute in 2019 across the Maurice Ewing Bank, the high-altitude easternmost section of the Falkland Plateau in the SW South Atlantic, are integrated with information from DSDP Leg 36, Sites 327, 329, and 330 and Leg 71 Site 511. A seismostratigraphic model is defined, including five units ranging in age from the Middle Jurassic to Quaternary and are interpreted with respect to the evolutional history of the oceanic circulations in the South Atlantic sector of the Southern Ocean. Sedimentary sequences of late Cretaceous and early Paleogene include little and restricted evidence of current activity, attributable to shallow-intermediate depth connections between the developing South Atlantic and Southern Ocean. In contrast, sedimentary sequences of the late Eocene/Oligocene and Neogene reveal a strong history of current-related erosion and deposition. These features exhibit specific water-depth expressions attesting to the long-term activity of different water masses, in stable circulation patterns as those of the present day. We thus suggest that proto-Upper and -Lower Circumpolar Deep Waters have been shaping the bank since the Oligocene. This implies that this bathymetric high has been acting as a barrier for the deep and bottom water masses flowing within the Antarctic Circumpolar Current since its establishment about the Eocene-Oligocene boundary.

How to cite: Najjarifarizhendi, B. and Uenzelmann-Neben, G.: Footprints of palaeocurrents in sedimentary sequences of the Cenozoic across the Maurice Ewing Bank, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10739, https://doi.org/10.5194/egusphere-egu21-10739, 2021.

Benthic foraminifera are typical unicellular marine fauna forming calcareous tests that are commonly used as a proxy to infer the past climatic variabilities. To study the benthic foraminiferal response, we collected 146 samples from IODP hole 1138A, the Southern Ocean (Indian Sector, water depth of 1140 m). We computed various diversity parameters of benthic foraminifera, i.e., Shannon-weaver index (H(S)), Equitability (E'), Hurlbert's diversity index (Sm), Fisher's alpha index (α), and Species richness (S). The calculated diversity indices with the abundance of dominant early Oligocene (33.5 to 31.2 million years ago) benthic foraminifera taxa reveal significant palaeoceanographic changes viz. cooling and warming events in the Southern Ocean. The early Oligocene interval exhibits an unusual condition at hole 1138A dominated by high oxygen species, intermediate food supply, well-ventilated, cold, and corrosive bottom water condition. The calculated values of all diversity parameters increase from 33.7 Ma to 32.8 Ma while attaining the maximum from 32.8 Ma to 32.2 Ma, followed by a decreasing trend. The highest value of diversity parameters coincides with the Oi-1 events. The relative increase in the species diversity between Oi-1 (33.5 Ma) and Oi-1b (31.7 Ma) events correspond to the brief interruption of Warm Saline Deep Water (WSDW). The enhanced values of low species diversity by high seasonality and relatively cold, strong bottom-water currents after Eocene-Oligocene Transition (EOT; 33.9 Ma) and after Oi-1b (31.7 Ma) event relates to the intensification of Antarctic Circumpolar Current (ACC) and Antarctic Bottom Water (AABW) along with the substantial buildup of the southern hemisphere glaciation. The abrupt decrease of abundance of species such as Nuttallides umbonifera, Astrononion echolsi, and Uvigerina peregerina at the end of the studied interval (31.3 Ma) further corroborates the major southern hemisphere glaciation. The present study of the benthic foraminiferal abundance and diversity indices therefore reveals the cooling of the Southern Ocean at early and late stages of the studied interval interrupted by a short-lived warming event. The study further enhances the understanding of paleo-marine ecology by evaluating the response of deep-sea benthic foraminifera to global climate change.

Keywords: Kerguelen Plateau, Benthic Foraminifera, Southern Ocean, early Oligocene

How to cite: Kumar, R., Maurya, A. S., and Singh, D. P.: Effect of early Oligocene cooling on the deep-sea benthic foraminifera at IODP hole 1138A, Kerguelen Plateau (Southern Ocean), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6414, https://doi.org/10.5194/egusphere-egu21-6414, 2021.

How to cite: He, T.: High-Resolution Carbonate Variability in Red Earth Deposits: Implications for Water Cycling Dynamics during the Late Miocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2962, https://doi.org/10.5194/egusphere-egu21-2962, 2021.

Hole U1473 (32° 42.3622’ S; 57° 16.6880’ E), located on the summit of Atlantis Bank at the ultra-slow spreading Southwest Indian Ridge was drilled to 789.7 m below seafloor (mbsf) during IODP Expedition 360. It consists of massive gabbros cut by nearly 400 felsic veins, which are evolved, SiO₂- enriched lithologies comprising ~1.5 vol% of the drill core. They vary in composition from diorite to trondhjemite. For their formation, 3 endmember models are discussed: (1) fractional crystallization; (2) hydrous anatexis of mafic rocks; (3) liquid immiscibility in an evolved MORB system.

Mineral assemblages in the felsic veins include mainly plagioclase, amphibole, Fe-Ti oxides ± quartz and minor zircon, apatite, ± titanite, ± biotite, ± K-feldspar.

Vein minerals often show strong zoning, which is especially expressed in amphiboles clearly visible by their variation in color ranging from brown to green corresponding to compositions from pargasite via pargasitic amphiboles, magnesiohornblendes to tremolite/actinolite. Moreover, zoning patterns can be observed in plagioclases from the veins, in which their An contents vary from An₃₄ down to An₅. This is distinctly lower than in the plagioclases of the host gabbros, which are virtually unzoned.

Clinopyroxenes at the contact between felsic vein and host gabbro show reactions either towards orthopyroxene or amphibole. TiO₂ in brown pargasites in the host rock at the contact is enriched (up to ~4.6 wt%), whereas counterparts of the same crystals in the felsic veins are distinctly lower in TiO₂ varying from ~2.5 wt% down to 0.1 wt% TiO₂, associated with variation in color from brown to green. Calculated equilibrium temperatures based on Ti-content in amphibole (Ernst & Liu, 1998), consequently lead to higher formation temperatures for amphiboles in the host gabbro (up to ~1000 °C) compared to their counterparts in the veins, ranging from ~890 °C to ~500 °C.

Amphiboles contain ~0.2 wt% F and distinctively lower contents in Cl (with one exception found). Most amphiboles at the contact show a core-rim evolution trend with decreasing F and increasing Cl content, implying a magmatic formation with increasing influence of processes involving a hydrothermal fluid. Only one out of twenty-two investigated samples shows a trend vice versa.

The record of eutectic crystallization expressed by granophyric structures of quartz and plagioclase indicates that the felsic veins crystallized from a melt.

Ernst, W. G., & Liu, J. (1998). Experimental phase-equilibrium study of Al-and Ti-contents of calcic amphibole in MORB—A semiquantitative thermobarometer. American mineralogist, 83(9-10), 952-969.

How to cite: Engelhardt, A., Koepke, J., and Holtz, F.: IODP Hole 1473A (Atlantis Bank, SWIR) - Formation of felsic veins in gabbros: reactions at the contact between felsic melt and host rock, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2356, https://doi.org/10.5194/egusphere-egu21-2356, 2021.

A series of basaltic eruptions from 1963 to 1967 off the southern coast of Iceland produced the oceanic island of Surtsey. Investigations of this volcanic system provide a time-lapse window into the real-time alteration of basaltic tephra through interactions with meteoric water in a subaerial tuff cone and with seawater in submarine deposits. In 1979, a 181 m core was recovered from a borehole (SE-01) on the eastern flank of the Surtur vent. In 2017, the ICDP-supported SUSTAIN drilling project drilled two vertical cored boreholes (SE-02a, SE-02b) to 151 and 187 m below surface (m b.s.) parallel to the 1979 borehole, and an additional angled cored borehole (SE-03) to 354 measured depth. These newly recovered cores, in comparison with the 1979 core, have promoted research into alteration processes within the volcano over the half century since its eruption. The scientific drilling undertaken in both 1979 and 2017 provides data critical to investigating mechanisms and rates of mineralogical change in basalt, evolving material and magnetic properties, and the characterization of basalt-hosted microbial communities.

            Previous research, including mineralogical analyses and geophysical downhole logging, reveals a weakly altered region at ~143-155 m b.s. that corresponds with a submarine zone of cool seawater inflow.  The purpose of this study is to better understand processes in this zone by examining SE-02b drill core samples taken at 141.6 m b.s. (83-86 °C) with mineralogical analyses and at 148 m b.s. (83-84 °C) with magnetic analyses and microbial community analyses. Mapping of the weakly-consolidated basaltic tuff at micrometer-scale using synchrotron X-ray micro-diffraction and micro-fluorescence studies shows that the basalt is primarily composed of fresh sideromelane glass, volcanic crystals, and open voids. Olivine and labradorite are the principal volcanic minerals; they have begun to alter to lizardite and aluminous tobermorite, respectively. The basaltic glass has begun to alter to nanocrystalline clinochlore and smectitic clay mineral, mainly nontronite and montmorillonite. The abundance of fresh glass, however, confirms a weakly altered region of the volcano. Uniaxial and cubic single domain titanomagnetite is the principal magnetic remanence carrier in the glass, whereas the magnetic minerals in more highly altered zones of lapilli tuff, only a few meters distant, are more oxidized and exhibit different magnetic anisotropies, consistent with the growth of secondary titanomaghemite. The properties of magnetic remanence remained relatively stable in the cool seawater inflow zone but changed very rapidly during fluid-rock interactions at higher hydrothermal temperatures. The microbial community detected in the drill core sample at 148 m b.s. from SE-02b is dominated by taxa generally found in seawater such as Psychromonas, Glaciecola, Marinomonas and suggests a possible infiltration of microbial taxa from the seawater to the submarine deposit. This anomalously permeable, poorly-consolidated horizon provides a strong contrast to the characteristics of the well-lithified lapilli tuff deposits and demonstrates the potential for substantial variability in mineralogical, magnetic and microbial submarine processes in other Surtseyan volcanoes and seamount structures.

How to cite: Peterson, J., Jackson, M., Marquardt, J., Lippert, P., Tamura, N., Bergsten, P., Vannier, P., Klonowski, A., Knobloch, S., Marteinsson, V., and Gudmundsson, M.: Material, Magnetic, and Microbial Features of a Submarine Inflow ZoneTraversed by SUSTAIN Drill Cores, Surtsey Volcano, Iceland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6496, https://doi.org/10.5194/egusphere-egu21-6496, 2021.

(Bio-)geochemical processes in subseafloor sediments are closely coupled to global element cycles. To gain an improved understanding of changes in (bio-)geochemical conditions on geological timescales, we investigate sediment cores from a 1180 m deep hole in the Nankai Trough offshore Japan (Site C0023). The sediment cores were taken during International Ocean Discovery Program (IODP) Expedition 370 (Temperature Limit of the Deep Biosphere off Muroto), which aimed at exploring the prerequisites and limits of deep microbial life [1]. Over the past 15 Ma, Site C0023 has moved ~750 km relative to its present-day geographic position from the central Shikoku Basin to the Nankai Trough due to motion of the Philippine Sea plate [2]. During its tectonic migration, Site C0023 has experienced significant changes in depositional and thermal conditions as well as resulting (bio-)geochemical processes.

By combining a large set of complementary pore-water, solid-phase and rock magnetic data with sedimentation rates and sediment ages, our aim is to (1) reconstruct the evolution of (bio-)geochemical processes, especially the cycling of iron, along the tectonic migration, and to (2) investigate if iron(III) minerals are still available to serve as energy substrate for microbial respiration in the deep sediments. Our results demonstrate that a transition from organic carbon-starved conditions with predominantly aerobic respiration processes to an elevated carbon burial environment with increased sedimentation occurred at ~2.5 Ma. Higher rates of organic carbon burial as a consequence of an increased nutrient supply and primary productivity likely stimulated the onset of organoclastic iron and sulfate reduction, biogenic methanogenesis and anaerobic oxidation of methane. A significant temperature increase by ~50°C across the sediment column associated with trench-style sedimentation since ~0.5 Ma potentially increased the bioavailability of organic matter and enhanced biogenic methane production. The resulting shifts in reaction fronts led to a diagenetic transformation of iron (oxyhydr)oxides into pyrite in the lower organic carbon-starved sediments several millions of years after burial. We also show that high amounts of iron(III), which were preserved in the deeply buried sediments due to carbon-starved conditions are still available as energy substrate for microbially mediated processes at Site C0023.

Our study emphasizes that depositional and thermal changes ultimately driven by the tectonically induced migration have the potential to strongly influence and control geochemical conditions and (bio-)geochemical processes within the whole sediment column. Such studies are needed to gain a fundamental understanding of the coupling between depositional history, (bio-)geochemical processes and the resulting diagenetic overprint on geological timescales, thereby linking the sedimentary iron, sulfur and carbon cycles.

References:

[1] Heuer, V.B. et al., 2020. Science 370: 1230-1234.

[2] Mahony, S.H. et al., 2011. Bulletin 123: 2201-2223.

How to cite: Köster, M., Kars, M., Schubotz, F., Tsang, M.-Y., Morono, Y., Inagaki, F., Heuer, V. B., Kasten, S., and Henkel, S.: The influence of tectonic migration of ocean floor on (bio-)geochemical and diagenetic processes in subseafloor sediments from the Nankai Trough off Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4080, https://doi.org/10.5194/egusphere-egu21-4080, 2021.

We document the geometry of a massive sill at the root of an approximately 20-m high and 800 m-wide ring of hydrothermal formations, termed Ringvent, located 28.5 km off-axis on the northwestern flanking regions of the actively rifting Guaymas Basin (Gulf of California). Using petrophysical data collected during the IODP Expedition 385 and processed 2D seismic profiles, we present evidence on the mechanics of sill emplacement and how the related hydrothermal vent conduits were constructed. The currently active moderate-temperature hydrothermal vent field indicates that, despite being cold and crystallized, the magma plumbing system, is tapping into a deeper geothermal source of the basin. The vent system roots at the vertical end of the magma plumbing system with the top of the sill located at a depth range of 80 to 150 m below the seafloor. Our research aims at constraining how far deep the geothermal fluids are coming from, and identifying how close the hydrothermal system is from a steady-state condition, to draw implications for how frequently such a system may arise in nascent ocean basins.

How to cite: Galerne, C. Y., Lizarralde, D., Berndt, C., Neumann, F., Höfig, T. W., Stock, J. M., Peña-Salinas, M. E., Negrete-Aranda, R., and Teske, A. P. and the Expedition 385 Scientists: Magma plumbing system and associated hydrothermal vents in the Guaymas Basin - geometry and implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13015, https://doi.org/10.5194/egusphere-egu21-13015, 2021.

The MARUM-MeBo sea bed drilling technology is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen (Freudenthal and Wefer, 2013). Presently two drill rigs are in operation for drilling and coring down to more than 70 m (MARUM-MeBo70) and 200 m (MARUM-MeBo200), respectively. The robotic drill rig with the required drill tools is deployed on the seabed, where the drill string for conducting coring is assembled during the drilling operation. In addition to wireline core barrels a temperature probe can be used for measuring formation bottom hole temperature at discrete drilling depths by pushing the probe about 15 cm into the base of the bore hole. The temperature is logged for about 10 – 15 minutes in order to allow for dissipation of the frictional heat generated during pushing and equilibration to formation temperature. When the temperature measurement is completed, the probe is recovered out of the drill string and the drilling operation can be continued.

The trip out of the drill string after reaching the target drill depth can be used for logging of the geophysical properties within the borehole and the adjacent formation. A memory logging tool is lowered into the drill string with the sensor part penetrating through the drill bit. When the drill string is tripped out the probe is raised together with the drill string inside the borehole and conducts the geophysical measurements. This method called “logging while tripping” is especially suitable for unconsolidated sediments and logging in unstable borehole conditions, since the drill string stabilizes the borehole above the sensor part during the logging operation. For the MeBo drill rigs we have spectrum gamma ray, magnetic susceptibility, dual induction and acoustic probes available. The latter is also equipped with a temperature sensor for measuring borehole temperature. 

In this presentation we show examples from MeBo drilling campaigns where core drilling, borehole logging and formation temperature measurements where combined. A focus of this presentation is the analysis of borehole temperature measurements during trip out. We investigate how geothermal flux and lithological changes (i.e. thermal conductivity) influence the bore hole temperature measurement by modeling the temperature evolution within the borehole during drilling and trip out.

References:

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

How to cite: Freudenthal, T., Riedel, M., and Villinger, H.: Borehole logging and temperature measurements with the MARUM-MeBo sea bed drilling technology: Recent developments and scientific applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5904, https://doi.org/10.5194/egusphere-egu21-5904, 2021.