Contourite characterization and its discrimination from other deep‐water deposits in the Gulf of Cadiz contourite depositional system

This project was funded through the Joint Industry Project supported by BP, ENI, ExxonMobil, TOTAL, Wintershall Dea and TGS, within the framework of "The Drifters" Research Group at Royal Holloway University of London (RHUL), in conjunction with the projects CTM 2012-39599-C03, CGL2015-66835-P, CTM2016-75129C3-1-R, CGL2016-80445-R (AEI/FEDER, UE) and B-RNM-072-UGR18. This research used data and samples collected by IODP Expedition 339 aboard the Joides Resolution. Data was acquired at the XRF Core Scanner Lab at MARUM -Center for Marine Environmental Sciences, University of Bremen, Germany. Our thanks to Dr Javier Dorador (RHUL, UK) for the high-resolution core imaging treatment, to Dr David Roque (ICMAN-CSIC, Spain) for his help in the hydrographic panels from Fig. 2, and to Dr Angel Puga-Bernabeu (University of Granada, Spain) for revision that helped to improve the original version of the manuscript before submission. This study significantly benefited from discussions with all who attended the IODP Exp. 339 MOW meeting in Heidelberg (Germany) in January 2019. We would like to thank Associate Editor Dr Adam McArthur and the three reviewers, Dr Rachel Brackenridge, Dr Giancarlo Davoli and Dr Adriano Viana, for their positive and constructive comments that helped us improve the manuscript.Despite numerous efforts to properly differentiate between contourites and other deep‐water deposits in cores and outcrops, reliable diagnostic criteria are still lacking. The co‐occurrence of downslope and along‐slope sedimentary processes makes it particularly difficult to differentiate these relatively homogeneous deposits. The main aim of this paper is to identify differences in deep‐water sediments based on Principal Component Analysis of grain size and geochemistry, sedimentary facies, and reinforced by microfacies and ichnofacies. The sediments studied were obtained from two International Ocean Drilling Program Expedition 339 sites in mounded and sheeted drifts in the Gulf of Cadiz. The statistical approach led to the discernment of hemipelagites, silty contourites, sandy contourites, bottom current reworked sands, fine‐grained turbidites and debrites over a range of depositional and physiographic elements. These elements are linked to contourite drifts, the drift‐channel transition, the contourite channel and distal upper slope. When bottom currents or gravity‐driven flows are not the dominant depositional process, marine productivity and continental input settling forms the main depositional mechanism in deep‐water environments. This is reflected by a high variability of the first principal component in hemipelagic deposits. The stacked principal component variability of these deposits evidences that the contourite drift and the adjacent contourite channel were influenced by the interrelation of hemipelagic, gravitational and bottom current induced depositional processes. This interrelation questions the paradigm that a drift is made up solely of muddy sediments. The interrelation of sedimentary processes is a consequence of the precession‐driven changes in the intensity of the Mediterranean Outflow Water related to Mediterranean climate variability, which are punctuated by millennial‐scale variability. Associated vertical and lateral shifts of the Mediterranean Outflow Water, and therefore of its interface with the East North Atlantic Central Water, controlled sediment input and favoured turbulent sediment transport in the middle slope. During the interglacial precession maxima/insolation minima, a more vigorous upper core of the Mediterranean Outflow Water and the enhanced impact of the East North Atlantic Central Water – Mediterranean Outflow Water interface allowed for the development of the sandier contourite deposits.BP within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)ENI within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)ExxonMobil within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)TOTAL within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)Wintershall Dea within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)TGS within the "The Drifters" Research Group at Royal Holloway University of London (RHUL)AEI/FEDER, UE CTM 2012-39599-C03 CGL2015-66835-P CTM2016-75129C3-1-R CGL2016-80445-RB-RNM-072-UGR1

Beryllium isotope variations recorded in the Ad´elie Basin, East Antarctica reflect Holocene changes in ice dynamics, productivity, and scavenging efficiency

The Ad´elie Basin is a relatively small (~1600 km2), semi-enclosed continental shelf bathymetric depression located adjacent to the Wilkes Subglacial Basin, a basin underlying a sector of the East Antarctic Ice Sheet that contains ~3–4 m sea level equivalent of ice. Located within the Ad´elie Basin is a ~184 m thick laminated sediment deposit, the Ad´elie Drift, ideal for examining regional changes in ice sheet and ocean dynamics. Here, we examine the ratio of reactive beryllium-10 to reactive beryllium-9 ((10Be/9Be)reac) in a marine sediment core obtained from the Ad´elie Drift to assess these changes during the Holocene epoch (11.7 ka BP to present). The (10Be/9Be)reac record provides insight into changes in freshwater input, primary productivity, and scavenging efficiency, while removing the influence of particle size on 10Be concentration. During the early Holocene, (10Be/9Be)reac ratios indicate increased meltwater discharge from ca. 11.7 to 10 ka BP, as grounded ice retreated from the Ad´elie Basin and adjacent bathymetric highs. After ~10 ka BP, beryllium isotopes are influenced by scavenging efficiency and dilution controlled by ocean currents and accumulation rate, operating alongside meltwater input, suggesting there are additional factors to consider when using (10Be/9Be)reac as a proxy for ice shelf cover and glacial dynamics.Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) 20H00193Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science 20J21145 PE17712 P18791New Zealand Ministry of Business, Innovation and Employment (MBIE) ANTA1801Ministry of Science and Innovation, Spain (MICINN)Spanish Government CTM2017-89711-C2-1-PEuropean Union through FEDER fund

Evidences of the Blake and Iceland Basin magnetic excursions in southeastern Iberia and chronological implications for the Padul sedimentary record

Acknowledgments This study was supported by the project B-RNM-144-UGR18 and ARNM- 336-UGR20 of the action “Proyectos I + D + i del Programa Operativo FEDER 2018 - Junta de Andalucía-UGR”, the projects CGL2013-47038-R and CGL2017-85415-R, of the “Ministerio de Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional FEDER”, and the research group RNM-190 (Junta de Andalucía), and the projects P18-RT-871 and Retos P20_00059 of Junta de Andalucia. A.G.-A. was also supported by a Ram´on y Cajal Fellowship RYC-2015-18966 of the Spanish Government (Ministerio de Economía y Competividad). A.L.-A PhD is funded by BES-2018-084293 (Ministerio de Economía y Competividad). We thank the Paleomagnetic Laboratory CCiTUB-Geo3Bcn CSIC for the support on paleomagnetic analysis. LV and EB thank the Geomodels Research Institute (UB). We are very grateful to two anonymous reviewers and to the editor Christian Zeeden.The Padul-15-05 sediment core provides an exceptional perspective of the paleoenvironmental and climate change in the Western Mediterranean region for the last ca. 200 kyr. However, even though a robust chronology mainly relying on radiometric dating is available for the last 50 ka, the chronology for the older sediments is not yet fully resolved. Ages for the bottom part of the core (>21 m) were previously inferred from amino-acid racemization dating and sediment accumulation rates. In this work, we provide a more accurate chronology for the older part (>100 kyr) of the Padul-15-05 sediment core record based on the recognition of past Earth's magnetic excursions. We identify an interval prone of reversed polarity samples close to MIS-5e/5 d transition that we correlate to the Blake geomagnetic excursion (116.5 kyr–112 kyr). In addition, we identify an interval of low inclinations and two reversed samples that we interpret as the Iceland Basin geomagnetic excursion (192.7 kyr–187.7 kyr: wide scenario of VGP <40°). Our new results, which include IRM acquisition curves that contribute to understand the magnetic mineralogy, enhances the robustness of the age model for the Padul-15-05 sedimentary sequence by adding an independent age dataset with new accurate tie-points. Our refined age control together with the available paleoenvironmental and paleoclimate multiproxy data provide insightful information to unveil the response of the western Mediterranean environments to regional environmental and climate change.Project B-RNM-144-UGR18 and ARNM- 336-UGR20 of the action “Proyectos I + D + i del Programa Operativo FEDER 2018 - Junta de Andalucía-UGR”Projects CGL2013-47038-R and CGL2017-85415-R, of the “Ministerio de Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional FEDER”Research group RNM-190 (Junta de Andalucía)Projects P18-RT-871 and Retos P20_00059 of Junta de AndaluciaRamón y Cajal Fellowship RYC-2015-18966 of the Spanish Government (Ministerio de Economía y Competividad)Funded by BES-2018-084293 (Ministerio de Economía y Competividad

Algal lipids reveal unprecedented warming rates in alpine areas of SW Europe during the industrial period

Alpine ecosystems of the southern Iberian Peninsula are among the most vulnerable and the first to respond to modern climate change in southwestern Europe. While major environmental shifts have occurred over the last similar to 1500 years in these alpine ecosystems, only changes in the recent centuries have led to abrupt environmental responses, but factors imposing the strongest stress have been unclear until now. To understand these environmental responses, this study, for the first time, has calibrated an algal lipid-derived temperature proxy (based on long-chain alkyl diols) to instrumental historical data extending alpine temperature reconstructions to 1500 years before present. These novel results highlight the enhanced effect of greenhouse gases on alpine temperatures during the last similar to 200 years and the long-term modulating role of solar forcing. This study also shows that the warming rate during the 20th century (similar to 0.18 degrees C per decade) was double that of the last stages of the Little Ice Age (similar to 0.09 degrees C per decade), even exceeding temperature trends of the high-altitude Alps during the 20th century. As a consequence, temperature exceeded the preindustrial record in the 1950s, and it has been one of the major forcing processes of the recent enhanced change in these alpine ecosystems from southern Iberia since then. Nevertheless, other factors reducing the snow and ice albedo (e.g., atmospheric deposition) may have influenced local glacier loss, since almost steady climate conditions predominated from the middle 19th century to the first decades of the 20th century.Peer reviewe

Late Holocene climate variability in the southwestern Mediterranean region: an integrated marine and terrestrial geochemical approach

10 páginas, 5 figuras, 1 tabla.A combination of marine (Alboran Sea cores, ODP 976 and TTR 300 G) and terrestrial (Zoñar Lake, Andalucia, Spain) geochemical proxies provides a high-resolution reconstruction of climate variability and human influence in the southwestern Mediterranean region for the last 4000 years at inter-centennial resolution. Proxies respond to changes in precipitation rather than temperature alone. Our combined terrestrial and marine archive documents a succession of dry and wet periods coherent with the North Atlantic climate signal. A dry period occurred prior to 2.7 cal ka BP – synchronously to the global aridity crisis of the third-millennium BC – and during the Medieval Climate Anomaly (1.4–0.7 cal ka BP). Wetter conditions prevailed from 2.7 to 1.4 cal ka BP. Hydrological signatures during the Little Ice Age are highly variable but consistent with more humidity than the Medieval Climate Anomaly. Additionally, Pb anomalies in sediments at the end of the Bronze Age suggest anthropogenic pollution earlier than the Roman Empire development in the Iberian Peninsula. The Late Holocene climate evolution of the in the study area confirms the see-saw pattern between the eastern and western Mediterranean regions and the higher influence of the North Atlantic dynamics in the western Mediterranean.Projects LIMNOCLIBER REN 2003-09130- C02-02, CALIBRE CGL 2006-13327-c04/CLI, CGL-2006-2956- BOS, CGL2009-07603 (MICINN), 200800050084447 (MARM) and RNM 05212 (Junta de Andalucía), we also thanks Projects GRACCIE (CSD2007- 00067) and CTM2009-07715 (MICINN), Research Group 0179 (Junta de Andalucía) and the Training- Through-Research Programme.Peer reviewe

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

Pliocene deglacial event timelines and the biogeochemical response offshore Wilkes Subglacial Basin, East Antarctica

Significantly reduced ice coverage in Greenland and West Antarctica during the warmer-than-present Pliocene could account for ∼10m of global mean sea level rise. Any sea level increase beyond this would require contributions from the East Antarctic Ice Sheet (EAIS). Previous studies have presented low-resolution geochemical evidence from the geological record, suggesting repeated ice advance and retreat in low-lying areas of the EAIS such as the Wilkes Subglacial Basin. However, the rates and mechanisms of retreat events are less well constrained. Here we present orbitally-resolved marine detrital sediment provenance data, paired with ice-rafted debris and productivity proxies, during three time intervals from the middle to late Pliocene at IODP Site U1361A, offshore of the Wilkes Subglacial Basin. Our new data reveal that Pliocene shifts in sediment provenance were paralleled by increases in marine productivity, while the onset of such changes was marked by peaks in ice-rafted debris mass accumulation rates. The coincidence of sediment provenance and marine productivity change argues against a switch in sediment delivery between ice streams, and instead suggests that deglacial warming triggered increased rates of iceberg calving, followed by inland retreat of the ice margin. Timescales from the onset of deglaciation to an inland retreated ice margin within the Wilkes Subglacial Basin are on the order of several thousand years. This geological evidence corroborates retreat rates determined from ice sheet modeling, and a contribution of ∼3 to 4m of equivalent sea level rise from one of the most vulnerable areas of the East Antarctic Ice Sheet during interglacial intervals throughout the middle to late Pliocene.Provenance analysis was supported by a Kristian Gerhard Jeb-sen PhD Scholarship and NERC UK IODP grants (NE/H025162/1 and NE/H014144/1). Biogenic silica data was supported by a Royal So-ciety of New Zealand Marsden FastStart grant (#UOO-1315) and a University of Otago PhD Scholarship. Support for sedimentol-ogyanalysis was provided by the Royal Society of New ZealandRutherford Discovery Fellowship (RDF-13-VUW-003). XRF work was supported by the Ministry of Science and Innovation Grant CTM2014-60451-C2-1-P co-financed by the European Regional De-velopment Fund (FEDER). Samples were provided by the Integrated Ocean Drilling Program

Gibraltar Outflow and Mediterranean overturning circulation during the last 500 ky

20th Congress of the International Union for Quaternary Research (INQUA). Dublin, 25th and 31st July 2019, AbstractsIn order to explore past changes in the Mediterranean Outflow Water (MOW) we analyzed the fine sand content in the sediments together with some geochemical proxies and planktic and benthic stable isotopes at IODP site U1389. This site was recovered in the vicinity of the Strait of Gibraltar along the path of the main core of the MOW. The content of fine sand together with Zr/Al ratios were used to investigate the MOW speed variability along the past 500 ky. The MOW speed variability at this site was mainly driven by changes in the density contrast between the Inflow and Outflow, which was, in turn, governed by changes in the Mediterranean heat and freshwater budgets. Events of enhanced freshwater input to the Mediterranean associated to northward shifts of the Intertropical convergence Zone reduced the density contrast at Gibraltar and weakened the MOW at Gibraltar. Weak MOW events were recorded at times of sapropel deposition in the eastern Mediterranean. At millennial scale, the MOW intensified at times of Greenland stadials and weakened during interstadials. However, during Heinrich stadials typical three-phase events were observed, with a sandy contourite layer at the bottom and top and a phase of weak MOW in the middle of the stadial, coinciding with the arrival of icebergs to the Gulf of Cadiz. For Heinrich stadial 1 this weak MOW event occurred at the time of the massive release of icebergs from the Laurentian ice sheets. However, the inflow of less saline water to the Mediterranean should have increased not decreased the density contrast between the Inflow and Outflow, especially because freshwater discharge to the Mediterranean from the African monsoons was extremely low. We propose different scenarios to explain these weak MOW events in the middle of Heinrich stadials that were certainly triggered by prominent changes in the Mediterranean heat and freshwater budget.Universidad de Salamanca, EspañaUniversity of Cambridge, Reino UnidoLeibniz-Laboratory for Radiometric Dating and Isotope Research, AlemaniaJapan Agency for Marine-Earth Science and Technology, JapónInstitute of Earth Sciences, Heidelberg University, AlemaniaRoyal Holloway, University of London, Reino UnidoSchool of Environmental Sciences, University of Hull, Reino UnidoInstituto Geológico y Minero de España, Españ