Environmental changes at the seafloor of the Faro drift (Gulf of Cadiz) during the transition from the Early to the Middle Pleistocene

Abstract. This 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 (δ18O and δ13C), 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.