The Indian-Atlantic Ocean gateway during the Pliocene: current dynamics and changing sediment provenance

The Pliocene epoch represents a discrete interval which reversed a long-term trend of late Neogene cooling and is also the most recent geological interval in which global temperatures were several degrees warmer than today. It is therefore often considered as the best analogue for a future anthropogenic greenhouse world. However, there is growing evidence that the Pliocene was not a stable period but can rather be subdivided in several distinct climate phases. Our understanding of Pliocene climate variability in the Southern Hemisphere, and especially in the Atlantic-Indian ocean gateway, is limited by scarce marine records and poor age control on existing terrestrial climate archives. At five drilling locations IODP Exp. 361 recovered high resolution complete late Miocene to Pleistocene sections (Hall et al., 2017). Our research proposal is based on the Sites U1474 (Natal Valley), U1475 (Agulhas Plateau), and U1479 (Cape Basin) forming a latitudinal transect. The main focus is on the interplay between northern and southern sourced deep water masses in the Atlantic-/Indian Ocean gateway during the Pliocene and combines chemical, physical property and seismic methods. Our research is driven by three working hypotheses: Seismic stratigraphies for the last 6 Ma and sediment drift growth in the Atlantic-Indian gateway are mainly controlled by bottom water flow changes Using the sediment archives and physical property records from IODP Exp. 361 we aim to construct and compare detailed seismic stratigraphies for the Agulhas Plateau, the Natal valley and the Cape basin for the last 6 Ma. At all Exp. 361 sites P-wave velocity and density records enable detailed correlations of drilling results and site survey data through the calculation of synthetic seismograms. Our working hypothesis implies that seismic reflection patterns and sediment accumulation during the Pliocene are closely linked to deep water circulation changes associated with climate Pliocene phases. Furthermore four distinct high latitude Pliocene glaciation events have been identified. We speculate that these phases and events have led to deep water circulation changes in Agulhas region, have altered the sediment physical properties and thus may be recognized as reflectors in the seismic profiles. How did the sediment input of terrigenous vs. biogenic sediment components in the gateway change during these events? Are these changes driven by dilution, dissolution, or productivity? We strive to answer these questions by interpreting edited and in-situ corrected physical core scanning records in combination major element variabilty derived from post cruise XRF-scanning. Trajectories and intensities of deep water masses in the Agulhas region during the Pliocene were influenced by Antarctic ice volume rather then by the closure of the Central American Seaway. The Exp. 361 drill sites offer the possibility to inter-correlate different flow speed proxies and to derive a detailed picture of flow changes during the Pliocene. By comparing core-measurements of sortable silt (S̅S̅), physical properties and XRF-core scanning data with seismic features we will tie the major flow speed changes to our seismic grid covering the Agulhas Plateau such that changing current intensities and pathways can be mapped together. Here we hypothesize that these changes are mainly driven by climate (Antarctic ice volume). How have the sedimentation patterns changed under the growing influence of North Atlantic Deep Water (NADW) during the Pliocene? What were the main changes associated with the instability of Antarctic ice sheets and was the production of Antartic Bottom Water (AABW) reduced or enhanced during these intervals? Was there also a potential influence of tectonic processes on the flow changes in the Agulhas region? Especially the closure of the Centarl American Seaway (CAS) in various phases between ~14 and ~2.7 Ma is thought to have had a profound impact on climate. Changes in physical and chemical sediment properties in the Agulhas region are largely controlled by earth’s orbital variations and allow a significant improvement of age models by cyclostratigraphy. Another primary objective of our research is the detection and characterization of orbital and sub-orbital cycles in the Agulhas sedimentary environment in relation to paleoceanographic changes. The presence of orbital cycles in ocean sediments has widely been used to derive high resolution age models in Cenozoic sediments. Typically orbital chronologies are based on benthic oxygen isotope records (δ18O) that are correlated to astronomical forcing functions (“orbital tuning”). However, the generation of such records at high resolution over long time intervals is time consuming and will likely not be completed for the Exp. 361 sites over the next years. In the absence of δ18O records cyclic changes in high resolution measurements of physical (e.g. density, colour reflectance, magnetic susceptibility) and chemical (major elements from XRF core scanning) parameters have been successfully used for orbital tuning. At the Exp. 361 Sites very regular cyclic amplitude changes are evident in the Pliocene sections, but up to now have not been further investigated. Which orbital frequency do these cycles represent and how do the dominent frequencies change over time? What is the potential of the observed cycles for stratigraphic purposes? We will analyse those cyclicities in the depth and time domain and strive to generate orbitally tuned time series of sediment provenance

GSH Attenuates Organ Injury and Improves Function after Transplantation of Fatty Livers

Ischemia-reperfusion injury (IRI) is increased after transplantation of steatotic livers. Since those livers are increasingly used for transplantation, protective strategies must be developed. Reactive oxygen species (ROS) play a key role in hepatic IRI. In lean organs, glutathione (GSH) is an efficient scavenger of ROS, diminishing IRI. The aim of this study was to evaluate whether GSH also protects steatotic allografts from IRI following transplantation. Fatty or lean livers were explanted from 10-week-old obese or lean Zucker rats and preserved (obese 4 h, lean 24 h) in hypothermic University of Wisconsin solution. Arterialized liver transplantation was then performed in lean syngeneic Zucker rats. Recipients of fatty livers were treated with GSH (200 mu mol/h/kg) or saline during reperfusion (2 h, n = 5). Parameters of hepatocellular damage and bile flow were measured. Transplantation of steatotic livers enhanced early reperfusion injury compared to lean organs as measured by increased aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase plasma levels. Bile flow was also reduced in steatotic grafts. Intravenous administration of GSH effectively decreased liver damage in fatty allografts and resulted in improved bile flow. Intravenous application of GSH effectively reduces early IRI in steatotic allografts and improves recovery of these marginal donor organs following transplantation. Copyright (C) 2010 S. Karger AG, Base

IODP Expedition 361 – Southern African Climates and Agulhas LGM Density Profile

IODP Expedition 361 drilled six sites (U1474 – U1479) on the southeast African margin and the Indian-Atlantic ocean gateway from 30 January to 31 March 2016. The sites, situated in the Mozambique Channel, Natal Valley, Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the Greater Agulhas Current System over the past ~5 Ma. More specifically, the main objectives of Expedition 361 were: (i) to establish the sensitivity of the Agulhas Current to climate change during the Plio-Pleistocene in association with transient to long-term changes of high-latitude climates, tropical heat budgets, and the monsoon system; (ii) to determine the dynamics of the Indian-Atlantic gateway circulation in association with changing wind fields and migrating ocean fronts; (iii) to examine the connection of the Agulhas leakage and the Atlantic Meridional Overturning Circulation; (iv) to address the influence of the Agulhas Current on African terrestrial climates, notably rainfall patterns and river runoff, and potential links to hominid evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples aiming at constraining the temperature and salinity profiles of the ocean during the Last Glacial Maximum. In total, 5175 m of core was recovered (average recovery 102 %) from a region poorly represented in the database of drill sites for scientific purposes. Physical property records derived from core-logging of the recovered sequences allowed complete spliced stratigraphic sections to be generated that span the interval of 0 to between ~0.13 and 7 Ma. A high-resolution program of interstitial water samples was carried out at Sites U1474, U1475, U1476, and U1478. The expedition made major strides toward fulfilling the scientific objectives despite of ~11 days of lost operational time due to weather conditions, a medical evacuation, and delays in attaining the necessary permissions to operate in Mozambique exclusive economic zone waters. Site U1474 (3034 meters below sea level [mbsl]), located in the northernmost Natal Valley, consists of eight holes ranging in penetration depth from 3.1 to 254.1 m drilling depth below seafloor (dsf). A total of 910.8 m of sediment was recovered, predominantly consisting of foraminifer-bearing clay with nannofossils. Based on the shipboard bio- and magnetistratigraphic datums, the sedimentary sequence extends back to the late Miocene (~6.2 Ma). This record represents the only site situated beneath the main flow of the fully constituted Agulhas Current and therefore provides the opportunity for high-resolution climate reconstructions of Agulhas Current warm-water transports and upstream variability that may allow the identification of connections between Agulhas leakage and its headwater variability. It also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets and the links to the cultural evolution of early modern humans. Site U1475 (2669 mbsl), located on the southwestern flank of the Agulhas Plateau, consists of six holes ranging in penetration depth from 1.5 to 277.0 m dsf. A total of 1015.9 m of sediment was recovered, predominantly consisting of nannofossil ooze. Shipboard bio- and magnetistratigraphic data suggest that the sedimentary sequence extends back to the late Miocene (~7 Ma). This record provides the opportunity for high-resolution climate reconstructions of the Agulhas Return Current and connections with the Sub-Tropical Front, productivity, and deep-water circulation. Site U1476 (2165 mbsl), located at the northern entrance of the Mozambique Channel, consists of five holes ranging in penetration depth from 5.7 to 234.8 m dsf. A total of 873.8 m of sediment was recovered, predominantly consisting of foraminifer-rich nannofossil ooze. The sedimentary sequence extends back to the late Miocene (~6.9 Ma), as inferred from the shiboard bio- and magnetostratigraphic data. The site boasts excellent biostratigraphy and notably cyclic physical properties. It therefore provides the opportunity for high-resolution reconstructions of tropical faunal assemblages, which will allow identification of connections be¬tween Agulhas leakage and its headwater variability. It also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets and thermocline and deep-water variability with likely links to the development of the Indonesian Throughflow as well as aridification of east Africa. Because of the excellent preservation of foraminifers, this an ideal site for a long record of surface-ocean pH from boron isotopes. Site U1477 (429 mbsl), located in the western Mozambique Channel east of the Zambezi River delta, consists of three holes ranging in penetration depth from 119.4 to 181.2 m dsf. A total of 490.0 m of sediment was recovered, predominantly consisting of sandy clay with foraminifers and nannofossils. Based on correlations to a nearby 14C dated cores and two biostratigrahic markers, the sedimentary sequence extends back to the Late Pleistocene (~0.13 Ma). The extreme accumulation rate (~1 m/ky) at this site provides the opportunity for exceptionally high resolution reconstructions of terrestrial climate and thermocline characteristics during the last glacial cycle. Site U1478 (488 mbsl), located in the western Mozambique Channel east of the Limpopo River delta, consists of four holes ranging in penetration depth from 216.0 to 248.4 m dsf. A total of 922.1 m of sediment was recovered, predominantly consisting of sand or clayey/sandy silt with foraminifers and nannofossils. The shipboard age-model suggests that the sedimentary sequence extends back to the Pliocene (~4 Ma). This record provides the opportunity for high-resolution climate reconstructions of faunal, biogeochemical, and terrigenous tracers that are characteristic of the upper reaches of the Agulhas Current warm-water transports that will allow connections between Agul¬has leakage and its headwater variability. The site also holds significant potential to investigate the connections between southern African terrestrial climates and southeast Indian Ocean heat budgets, and examine the relationship between such climate variability and early human evolution. Site U1479 (2615 mbsl), located in Cape Basin, consists of nine holes ranging in penetration depth from 1.0 to 300.7 m dsf. A total of 963.1 m of sediment was recovered, predominantly consisting of nannofossil ooze with or without foraminifers. According to the shipboard bio- and magnetostratigraphy-based age model, the sedimentary sequence extends back to the late Miocene (~7 Ma). This record represents the only site situated in the immediate Agulhas leakage pathway. It will therefore provide the opportunity for high-resolution climate reconstructions of the leakage and temporal comparisons with deep-water circulation

VSHOT: a tool for characterizing large, imprecise reflectors

A prototype Video Scanning Hartmann Optical Tester (VSHOT) has been developed to characterize the optics of dish-type solar concentrators. VSHOT is a flexible platform that may characterize any large reflector with a focal length over diameter ratio (f{number_sign}) greater than 0. 45, and RMS optical error in the 0. I - I 0 milliradian range. The VSHOT hardware, software, and operation are described. Measurement uncertainty and preliminary test results are discussed. Another potential application being explored for the VSHOT is the quality assurance of slumped-glass automobile windshields. Preliminary test results from a reference optic and a section of a windshield are presented

Expedition 306 summary

The overall aim of the North Atlantic paleoceanography study of Integrated Ocean Drilling Program Expedition 306 is to place late Neogene–Quaternary climate proxies in the North Atlantic into a chronology based on a combination of geomagnetic paleointensity, stable isotope, and detrital layer stratigraphies, and in so doing generate integrated North Atlantic millennial-scale stratigraphies for the last few million years. To reach this aim, complete sedimentary sections were drilled by multiple advanced piston coring directly south of the central Atlantic “ice-rafted debris belt” and on the southern Gardar Drift. In addition to the North Atlantic paleoceanography study, a borehole observatory was successfully installed in a new ~180 m deep hole close to Ocean Drilling Program Site 642, consisting of a circulation obviation retrofit kit to seal the borehole from the overlying ocean, a thermistor string, and a data logger to document and monitor bottom water temperature variations through time

Multi-segment coherent beam combining

Scaling laser systems to large sizes for power beaming and other applications can sometimes be simplified by combing a number of smaller lasers. However, to fully utilize this scaling, coherent beam combination is necessary. This requires measuring and controlling each beam`s pointing and phase relative to adjacent beams using an adaptive optical system. We have built a sub-scale brass-board to evaluate various methods for beam-combining. It includes a segmented adaptive optic and several different specialized wavefront sensors that are fabricated using diffractive optics methods. We have evaluated a number of different phasing algorithms, including hierarchical and matrix methods, and have demonstrated phasing of several elements. The system is currently extended to a large number of segments to evaluate various scaling methodologies

Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean

This work used samples and data provided by the IODP. We are thankful for the support from the crew of the R/V JOIDES Resolution and IODP staff. This work is funded through the Universidad de Salamanca Postdoctoral Contract supported by the Ministerio de Ciencia, Innovacion y Universidades Grant RTI2018-099489-B-I00 and the German Science Foundation (DFG) Research Center/Cluster of Excellence 'The Ocean in the Earth System' (MARUM; Grant No. 49926684). We acknowledge financial support from the National Science Foundation of the US under Award No. 1737218 (M.A.B), the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant Agreement No. 799531 (M.S.P.), and the Spanish Ministry of Science and Innovation Grant CTM2017-89711-C2-1-P, co-funded by the European Union through FEDER funds (F.J.J.E.).In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations.Universidad de Salamanca - Ministerio de Ciencia, Innovacion y Universidades Grant RTI2018-099489-B-I00German Research Foundation (DFG) 49926684National Science Foundation (NSF) 1737218European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant 799531Spanish Government CTM2017-89711-C2-1-PEuropean Union through FEDER fund

Slip-rate on the Main Köpetdag (Kopeh Dagh) strike-slip fault, Turkmenistan, and the active tectonics of the South Caspian

We provide the first measurement of strike-slip and shortening rates across the 200-km-long right-lateral strike-slip Main Köpetdag Fault (MKDF) in Turkmenistan. Strike-slip and shortening components are accommodated on parallel structures separated by ∼10 km. Using Infra-red-stimulated luminescence and reconstruction of offset alluvial fans we find a right-lateral rate of 9.1 ± 1.3 mm/yr averaged over 100 ± 5 ka, and a shortening rate of only ∼0.3 mm/yr averaged over 35 ± 4 ka across the frontal thrust, though additional shortening is likely to be accommodated locally by folding and faulting, and regionally within the eastern Caspian lowlands to its south. The MKDF is estimated to have ∼35 km of cumulative right-lateral slip which, if these geological measurements are correct, would accumulate in only 3–5 Ma at the rate we have determined, suggesting that the present tectonic configuration started within that time period. We use the MKDF slip-rate to form a velocity triangle, from which we estimate the Iran-South Caspian and Eurasia-South Caspian shortening rates, and show that the South Caspian Basin moves at 10.4 ± 1.1 mm/yr in direction 333° ± 5 relative to Eurasia and at 4.8 ± 0.8 mm/yr in direction 236° ± 14 relative to Iran. In contrast to both the eastern Köpetdag and the Caspian lowlands the MKDF has little recent or historical seismicity. The rapid slip-rate estimated here suggests that it is a zone of high earthquake hazard

Orbitally-controlled variations of physical properties and sediment provenance in Indian-Atlantic Ocean gateway over the last 7 Ma

In 2016 the International Ocean Discovery Program (IODP) Expedition 361 (“SAFARI”) recovered complete high-resolution Plio-/Pleistocene sediment sections at six drilling locations on the southeast African margin and at the oceanic connection between the Indian and South Atlantic Oceans. Site U1475 is located on the southern flank of the Agulhas Plateau, proximal to the entrance of North Atlantic Deep Water (NADW) to the Southern Ocean and South Indian Ocean. The site was drilled into a sediment drift in 2669 m water depth and comprises a complete carbonate rich (74 – 85%) stratigraphic section of the last ~7 Ma. The contourite deposits hold detailed information on past changes in the bottom water flow history in the Indian-Atlantic ocean gateway. Here we present results from the integration of physical properties, seismic reflection data, and major element records. The whole spliced sediment record (292 meters) of Site U1475 was measured using an X-ray fluorescence (XRF) core scanner to derive multi-centennial resolution records of major element intensities. Based on these measurements it is possible to derive biogenic (e.g. %CaCO3) and siliciclastic (e.g. TiO2, K2O) mineral phases. Elemental log-ratios, such as Ca/Ti and K/Fe, reflect variations in biogenic (CaCO3) vs. terrigenous supply and variability of the terrigenous provenance, respectively. While long-term changes in physical properties and elemental ratios can be linked to the seismic reflection patterns associated with deep water circulation changes, short-term cyclicities reflect Plio-Pleistocene climate variations at Milanlovitch-frequencies. Evolutionary spectra show that the orbital control on sediment composition was variable over time. During the last 4 Ma energy is concentrated at the 41ka band of obliquity and at lower frequencies. In contrast, the orbital precession cycle (19-23ka) is very prominent in a peculiar high sedimentation rate interval in the early Pliocene (~4 to 5 Ma) that is bounded by seismic reflectors and characterized by the development of sediment waves