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2.1 Latest Achievements in Scientific Ocean and Continental Drilling
by Martin Ziegler1, Timme Donders1, Jan Behrmann2, Lucas Lourens1
1: Utrecht University, Netherlands; 2: GEOMAR, Kiel, Germany
National and international Earth science programs are utilizing Scientific Drilling as a critical tool to understand climate and environmental variability, natural hazards such as earthquakes and volcanic eruptions, natural resources, the deep biosphere and other topics of socio-economic relevance. The principal goal of the session is to summarize latest scientific achievements in ocean, continental and polar drilling.
3:20pm - 3:35pm
Invited Virtual Presentation | Keynote
New insights in the Late Pliocene and Early Pleistocene vegetation and climate stratigraphy of NW Europe
1Faculty of Geosciences, Utrecht University, The Netherlands; 2Geological Survey of the Netherlands, Utrecht, The Netherlands; 3The University of Manchester, Manchester, UK
The chronostratigraphy and climate record of the Late Pliocene and Early Pleistocene in Northwest Europe was spurred by pioneering work in the 1960’s by Waldo Zagwijn. This period is particularly important because of the inception of ice sheets in the Northern Hemisphere. However, the classic stratigraphic framework based on palynology is difficult to couple to the Marine Isotopic Stages (MIS) due to a lack of independent dating of the terrestrial deposits. The type area in the Dutch-German border area is characterized by a complex local stratigraphy and represents an incomplete sedimentary record.
We aim to reconstruct a new stratigraphic composite reference section for the Late Pliocene and Lower Pleistocene of the shallow marine to deltaic deposits of the north-western Netherlands and North Sea. Recent borehole analyses show clear Late Pliocene to earliest Pleistocene interglacial-glacial cyclicity in the Netherlands, expressing variation in sediment supply, large-scale landscape reorganisation and terrestrial temperature variation.
A new 380 m deep onshore borehole targets Early Pleistocene vegetation and marine ecosystem change, in relation to the glacioeustatic and paleoclimatic cyclicity. The shallow-marine to deltaic facies are logged in detail and yield well-preserved and diversified pollen and organic-walled dinoflagellate cyst associations. New onshore and offshore paleomagnetic data allow an improved tie of the terrestrial pollen zones to the MIS‘s. The integrated marine- and terrestrial palynostratigraphic framework for the Late Pliocene and Early Pleistocene of the Netherlands, in a scientific drilling framework, will lead to improved reconstructions of climate, sea-level and sediment provenance.
3:35pm - 3:50pm
Virtual Presentation | ECS
North Atlantic sea surface temperature evolution across the Eocene–Oligocene transition
1Utrecht University, Netherlands, The; 2Unviersity of Bergen, Norway
The Eocene–Oligocene Transition (EOT, ~34 Ma), is marked by the rapid development of semi-permanent Antarctic ice-sheet1. Foraminiferal stable oxygen isotopes (δ18O) as well as Mg/Ca and other indicators (e.g. ice-rafted debris) indicate the development of permanent glaciation that potentially coincides with ~2.5 °Cdeep-sea cooling2. However, due to the nature of the δ18O proxy, uncertainties in the Mg/Ca concentrations of the palaeo-seawater, and calibration extrapolation/saturation to/at higher temperatures for organic proxies, it remains unclear how sea surface temperature (SST) changed across the EOT.
In this study, we apply clumped-isotope palaeothermometry to well-preserved planktic foraminifera from the drift sediments of IODP Site 1411, Newfoundland, across four intervals bracketing the EOT. Initial findings indicate minor cooling across the interval, with absolute temperatures that are significantly lower than those reconstructed using other proxies3, a discrepancy that warrants further research.
1: Coxall, H. K., & Pearson, P. N. (2007). The Eocene-Oligocene transition. Deep Time Perspectives on Climate Change: Marrying the Signal From Computer Models and Biological Proxies, p. 351-387.
2: Lear, C. H., Bailey, T. R., Pearson, P. N., Coxall, H. K. & Rosenthal, Y. (2008) Cooling and ice growth across the Eocene-Oligocene transition. Geology 36, p. 251–254.
3: Liu, Z., He, Y., Jiang, Y., Wang, H., Liu, W., Bohaty, S. M., & Wilson, P. A. (2018). Transient temperature asymmetry between hemispheres in the Palaeogene Atlantic Ocean. Nature Geoscience, 11(9), p. 656.
3:50pm - 4:05pm
Southeastern Atlantic deep-sea warmth across two early Eocene transient global warming events
Paleoclimate & Biogeology, Earth Sciences Department, Utrecht University, The Netherlands
The early Eocene (56–48 Ma) can provide important constraints on the near-future warm climate state (Zachos et al., 2008; Burke et al., 2018) because it is a greenhouse period of highly-elevated CO2 levels and the occurrence of multiple transient global warming events (hyperthermals) (e.g. Lourens et al., 2005; Sluijs et al., 2006; Bijl et al., 2009; Anagnostou et al., 2016; Cramwinckel et al., 2018; Lauretano et al., 2018). Given the large heat capacity of the deep ocean, deep-sea temperatures are arguably the best indicator for mean global temperature change. Here we apply for the first time the clumped isotope technique (Δ47) on early Eocene benthic foraminifera to better constrain absolute deep water temperatures across two hyperthermal events in the Southeastern Atlantic. Our results indicate warmer background deep-sea conditions, and larger high-temperature variability associated with these warming events than previously estimated based on foraminiferal δ18O and Mg/Ca. Assuming our temperatures are representative for the global deep ocean, the robust reconstructions of early Eocene deep-sea temperatures that we provide may indicate higher climate sensitivity for these past warm climates (or alternatively higher CO2 forcing).
4:05pm - 4:20pm
Characterizing sediment dewatering and fluid flow in accretionary systems – A rock magnetic approach on the example of IODP Site U1518
1Paleomagnetic Laboratory 'Fort Hoofddijk', Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands; 2Center for Advanced Marine Core Research, Kochi University, Nankoku, Japan; 3Institute of Geosciences and Geography, Martin-Luther University Halle, Halle, Germany
The dewatering and subsequent drainage of fluids from porous sediments in forearc regions control the frictional behavior of the plate boundary décollement and all other faults in the forearc. Site U1518 of International Ocean Discovery Program (IODP) Expedition 375 penetrated the Pāpaku fault, a shallow splay fault near the deformation front of the Hikurangi Subduction Margin (New Zealand). We present rock magnetic datasets that help to depict strain history, and provide information on permeability anisotropy as well as the locus of fluid and gas migration across the fault zone.
A set of room temperature magnetic parameters was acquired on one sample per every meter of core recovered. Conspicuous are two anomalies at 304 - 312 m and 334 - 351 m (below seafloor), towards lower remanence intensity and coercivity. The upper interval coincides with an upper strand of high intensity fracturing and deformation within the Pāpaku fault, the lower interval to a sand-rich interval adjacent to a lower strand of high intensity deformation. Backscattered electron images show a significantly higher abundance of, and recrystallization of framboidal iron-sulfide minerals in this zone. We propose that the rock magnetic signature is due to the reduction of ferrimagnetic greigite (Fe3S4) to paramagnetic pyrite (FeS2). This is most likely caused by the drainage of methane-, and sulfide rich fluids/gas along high permeability zones. The results of magnetic fabric analyses conducted using the Anisotropy of Magnetic Susceptibility (AMS) indicate a sub-horizontal near fault-parallel alignment of paramagnetic clay minerals, which may have enhanced permeability anisotropy.
4:20pm - 4:35pm
A 5.3-million-year history of monsoonal precipitation in northwestern Australia
1NIOZ - Royal Netherlands Institute for Sea Research, and Utrecht University, Texel, the Netherlands; 2MARUM – Center for Marine Environmental Sciences, Bremen University, Bremen, Germany; 3Department of Earth Sciences, Faculty of Science, Vrije Universiteit Amsterdam, The Netherlands; 4ANU – Australian National University, Research School of Earth Sciences, Canberra, Australia; 5School of Geography, Earth and Environmental Sciences at University of Birmingham, Edgbaston Birmingham, United Kingdom; 6LSCE - Laboratoire des Sciences du Climate et de l’Environnement, Gif-sur-Yvette, France; 7University College London, UCL, dept of Earth Sciences, London, United Kingdom; 8Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, USA; 9JAMSTEC – Japan Agency for Marine Earth Science and Technology, Yokosuka, Japan
Australia is the driest inhabited continent on the planet, with its moisture mostly sourced from the tropical monsoon in the north and the southern westerlies in the south. The continent has experienced large climate fluctuations in the geologic past, but long continuous records of palaeo-environmental changes are lacking, particularly prior to ~0.55Ma. Here, we address this paucity by presenting a continuous record of continental aridity and monsoonal activity in northwestern Australia since the Pliocene (5.3 Ma). Our records are based on bulk-chemical XRF-scans and particle-size distributions of the terrigenous fraction, in two cores from the northwestern Australian continental shelf: MD002361 and ODP122-762B. In our records we distinguish between aeolian- and fluvial sediments that were deposited at sea. Support for the distinction between aeolian and fluvial sediment fractions in the two marine sediment cores is found in the bulk-chemical composition of aeolian- and fluvial material in the potential source areas in northern West Australia. Our records show a warm and dry early Pliocene (~5.3 Ma) on the northwestern Australian continent, which experienced a gradual increase in humidity peaking at about 3.8 Ma with higher than present-day rainfall. Between 3.8 and about 2.8 Ma, climate became progressively more arid with more rainfall variability. Coinciding with the onset of the northern hemisphere glaciations and the intensification of the northern-hemisphere monsoon, aridity continued to increase overall from 2.8 Ma until today, with greater variance in precipitation and an increased frequency of large rainfall events. We associate the observed large-scale fluctuations in Australian aridity with variations in Indian Ocean sea-surface temperatures, which largely control the monsoonal precipitation in northwestern Australia.
4:35pm - 4:50pm
Virtual Presentation | ECS
Felsic veins in gabbros drilled by IODP at Atlantis Bank (Southwest Indian Ridge; Expedition 360): Formation, metamorphism and their role for fluid and mass transfer: first results
Leibniz University Hannover, Germany
Hole U1473 (32° 42.3622’ S; 057° 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 (Dick et al., 2015). For their formation 3 endmember models are discussed: (1) fractional crystallization as consequence of oxide saturation at a late stage of tholeiitic magma evolution; (2) anatexis of mafic rocks in the deep oceanic crust, triggered by hydrothermal fluids; (3) liquid immiscibility in an evolved MORB system. This project aims to clarify their formation, their metamorphic evolution and their role to act as pathways for transporting fluids into the deep crust.
Felsic veins are ubiquitous throughout hole U1473 crosscutting the host gabbros. Mineral assemblages in the felsic veins include plagioclase, amphibole, Fe-Ti oxides ± quartz, sometimes associated with accessory minerals as zircon, apatite, ± titanite, ± biotite, ± K-feldspar. The vein minerals often show strong zoning, which is especially expressed in amphiboles easily visible by their color ranging from brown to green (Fig. 1 a) corresponding to compositions from pargasite via pargasitic amphiboles, magnesiohornblendes to tremolite/actinolite. An contents of plagioclases in the veins vary from 33.55 down to 4.75, which is distinctly lower than in the plagioclases of the host gabbros. Clinopyroxenes directly on the contact between felsic veins and host gabbros show reactions towards amphibole (Fig. 1 d). In order to monitor the transition between magmatic and metamorphic processes amphiboles are well suited, with focus on the concentration of Ti, which is a function of formation temperatures (Ernst & Liu, 1998). Preliminary results display that TiO2 is generally strongly enriched in the host rock (up to ~4.5 wt%), decreasing gradually in the veins to very low contents (Fig. 1b).
The contents of F and Cl help to distinguish between magmatic and seawater derived fluids controlling the amphibole formation. Preliminary results show profiles in which Cl parallels the zoning pattern for TiO2 , whereas F seems to be unaffected (Fig. 1 c).
Characteristic features observed in ~1/3 of all samples are granophyric textures exposed as intergrowth of quartz and (albitic) plagioclase (Fig. 2a). Only in one sample we observed a special variety of this intergrowth. Here, both domains of the granophyric texture are plagioclase slightly varying in average composition, instead of plagioclase and quartz, (Fig. 2b, 2c). IODP/ICDP Kolloquium Hamburg 9.-11.3.2020 47 We believe that in this special situation quartz was replaced by albite, due to the presence of SiO2 undersaturated hydrothermal fluids.
4:50pm - 5:05pm
Virtual Presentation | ECS
Drillcore GT1 of the ICDP Oman Drilling Project: insights into magmatic processes beneath fast-spreading mid-ocean ridges
1Insitut für Mineralogie, Leibniz Universität Hannover, Germany; 2Géosciences Montpellier, Université de Montpellier, CNRS, Université des Antilles, Montpellier, France; 3Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel; 4Department of Earth and Environmental Sciences, University of Manchester, UK; 5different institutions of Earth Sciences worldwide
The Samail ophiolite in Oman provides an ideal field laboratory for investigating the processes taking place beneath fast-spreading mid-ocean ridges (MORs). Drill site GT1, which was sampled by the Oman Drilling Project in the frame of the International Continental Scientific Drilling Program (ICDP), is located in Wadi Gideah (Wadi Tayin massif). Here, a reference profile through the entire Oman paleocrust was established  such that GT1 can be embedded into the surface profile. The core was investigated with diverse petrographic, petrological, and microstructural tools in order to better understand the accretion of the lower crust at fast-spreading MORs.
The majority of the obtained samples are gabbros or olivine gabbros. Mg#s (Mg#=Mg/(Mg+Fe)x100; molar) vary between 74 and 86 in clinopyroxene, and between 70 and 83 in some primary olivine relicts. Ca# (Ca#=Ca/(Ca+Na)x100; molar) in plagioclase varies between 68 and 87. Both Mg#s and Ca# show distinct minima with progressively increasing trends both up and down section at 1050 m above the Moho. To quantify the pole figure symmetry, i.e. fabric, of plagioclase, we use the BA index  which varies between 0 for a purely foliated and 1 for a purely lineated fabric. BA correlates with the petrological data indicating a more foliated plagioclase fabric that correlates with the minima in Mg#s and Ca#, indicating stronger compacted and/or less sheared material at this horizon. We interpret the correlation between petrological and microstructural data as indicator for the influx of more evolved melt leading to a concurrent weakening of plagioclase lineation.
 Koepke, J., Garbe-Schoenberg, D., Mueller, T., Mueller, M., Mock, D., Strauss, H., Schuth, S., Ildefonse, B., 2017. A Reference Section through the Lower Fast-spreading Oceanic Crust in the Wadi Gideah (Sumail ophiolite, Sultanate Oman): Drill Sites GT1A and GT2A within the ICDP Oman Drilling Project Abstract V43G-2737: presented at 2017 Fall Meeting, AGU, New Orleans.
 Satsukawa, T., Ildefonse, B., Mainprice, D., Morales, L. F. G., Michibayashi, K., & Barou, F. (2013). A database of plagioclase crystal preferred orientations (CPO) and microstructures-implications for CPO origin, strength, symmetry and seismic anisotropy in gabbroic rocks. Solid Earth, 4(2), 511.
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