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- Environmental changes at the seafloor of the Faro drift (Gulf of Cadiz) during the transition from the early to the middle pleistocenePublication . Silveira Molina, Giulia; Schmiedl, Gerhard; Jiménez-Espejo, Francisco; Kuhnert, Henning; Anica Claro Rodrigues, Teresa Isabel; Voelker, AntjeThis study explores the ecology of the benthic foraminifera fauna and reconstructs bottom water oxygenation, organic matter fluxes, and Mediterranean Outflow Water (MOW) dynamics in the Gulf of Cadiz during the Early to Middle Pleistocene Transition (EMPT) interval of Marine Isotope Stage (MIS) 28 to MIS 19 (1014–761 ka) using high-resolution multiproxy data from IODP Site U1387. Along with benthic foraminifera assemblages, we integrate stable isotopes (δ 18O and δ 13C), organic carbon, alkenone concentrations, and geochemical and sedimentological proxies (Zr/Al ratio, grain size) to identify environmental drivers across glacial– interglacial cycles and millennial-scale events. Furthermore, the absolute abundance of Planulina ariminensis is applied as a proxy for bottom current strength. Principal component analysis confirms assemblage responses to variations in organic matter quality and oxygenation. Periods of intensified MOW during stadial climate stages correspond to enhanced bottom water ventilation, reflected in higher abundances of epifaunal and porcelaneous taxa, higher diversity, and increased dissolved oxygen, with the exception of the late MIS 22. Intervals of reduced ventilation (e.g. interglacial MIS 27, MIS 25e, MIS 21g, MIS 19c) coincide with higher total alkenone concentrations, potentially contributing to low oxygen conditions and increased proportions of infaunal taxa. Our results reveal that bottom water dynamics at Site U1387 were controlled by local oceanographic processes (e.g. coastal upwelling, river discharge, water column stratification) rather than by global ice volume changes only. These findings highlight the importance of understanding regional oceanographic variations during the EMPT and emphasize the value of combining food supply, oxygenation, and bottom current proxies to interpret benthic foraminifera ecological changes.
- Reviews and syntheses: review of proxies for low-oxygen paleoceanographic reconstructionsPublication . Hoogakker, Babette A.A.; Davis, Catherine; Wang, Yi; Kusch, Stephanie; Nilsson-Kerr, Katrina; Hardisty, Dalton S.; Jacobel, Allison; Macaya, Dharma Reyes; Glock, Nicolaas; Ni, Sha; Sepúlveda, Julio; Ren, Abby; Auderset, Alexandra; Hess, Anya V.; Meissner, Katrin J.; Cardich, Jorge; Anderson, Robert; Barras, Christine; Basak, Chandranath; Bradbury, Harold J.; Brinkmann, Inda; Castillo, Alexis; Cook, Madelyn; Costa, Kassandra; Choquel, Constance; Diz, Paula; Donnenfield, Jonas; Elling, Felix J.; Erdem, Zeynep; Filipsson, Helena L.; Garrido, Sebastián; Gottschalk, Julia; Menon, Anjaly Govindankutty; Groeneveld, Jeroen; Hallmann, Christian; Hendy, Ingrid; Hennekam, Rick; Lu, Wanyi; Lynch-Stieglitz, Jean; Matos, Lélia; Martínez-García, Alfredo; Silveira Molina, Giulia; Muñoz, Práxedes; Moretti, Simone; Morford, Jennifer; Nuber, Sophie; Radionovskaya, Svetlana; Raven, Morgan Reed; Somes, Christopher J.; Studer, Anja S.; Tachikawa, Kazuyo; Tapia, Raúl; Tetard, Martin; Vollmer, Tyler; Wang, Xingchen; Wu, Shuzhuang; Zhang, Yan; Zheng, Xin-Yuan; Zhou, YuxinA growing body of observations has revealed rapid changes in both the total inventory and the distribution of marine oxygen over the latter half of the 20th century, leading to increased interest in extending oxygenation records into the past. The use of paleo-oxygen proxies has the potential to extend the spatial and temporal range of current records, constrain pre-anthropogenic baselines, provide datasets necessary to test climate models under different boundary conditions, and ultimately understand how ocean oxygenation responds beyond decadal-scale changes. This review seeks to summarize the current state of knowledge about proxies for reconstructing Cenozoic marine oxygen: sedimentary features, sedimentary redox-sensitive trace elements and isotopes, biomarkers, nitrogen isotopes, foraminiferal trace elements, foraminiferal assemblages, foraminiferal morphometrics, and benthic foraminiferal carbon isotope gradients. Taking stock of each proxy reveals some common limitations as the majority of proxies functions best at low-oxygen concentrations, and many reflect multiple environmental drivers. We also highlight recent breakthroughs in geochemistry and proxy approaches to constraining pelagic (in addition to benthic) oxygenation that are rapidly advancing the field. In light of both the emergence of new proxies and the persistent multiple driver problem, the need for multi-proxy approaches and data storage and sharing that adhere to the principles of findability, accessibility, interoperability, and reusability (FAIR) is emphasized. Continued refinements of proxy approaches and both proxy–proxy and proxy–model comparisons are likely to support the growing needs of both oceanographers and paleoceanographers interested in paleooxygenation records.