A micropalaeontological perspective on export productivity, oxygenation and temperature in \{NE\} Atlantic deep-waters across Terminations I and İI\}

Abstract Census counts of benthic foraminifera were studied from the \{SW\} Iberian Margin to reconstruct past changes in deep-water hydrography across Terminations I and II. Detailed benthic faunal data (> 125 μm size-fraction) allow us to evaluate the limitations imposed by taphonomic processes and restricted size-fractions. The comparison of recent (mudline) and fossil assemblages at İODP\} Site \{U1385\} indicates the quick post-mortem disintegration of shells of astrorhizoid taxa (  80% of the present-day fauna), resulting in impoverished fossil assemblages. While the application of quantitative proxy methods is problematic under these circumstances, the fossil assemblages can still provide a qualitative palaeoenvironmental signal that, while most fully expressed in the 125–212 μm size-fraction, is nonetheless also expressed to some degree in the > 212 μm size-fraction. Variations in the benthic foraminiferal assemblages reveal information about changing organic matter supply, deep-water oxygenation and temperature. \{MIS\} 2 is generally characterized by an elevated trophic state and variable oxic conditions, with oxygenation minima culminating in the Younger Dryas (YD) and Heinrich Stadials (HS) 1, 2 and 3. Low oxic conditions coincide with decreased water-temperature and lower benthic δ13C, pointing to the strong influence of a southern sourced water-mass during these periods. \{HS\} 1 is the most extreme of these intervals, providing further evidence for a severe temporary reduction or even shutdown of AMOC. With the inception of \{MIS\} 1, organic matter supply reduced and a better ventilated deep-water environment bathed by \{NEADW\} is established. For Termination II, clear indications of southern-sourced water are limited to the early phase of \{HS\} 11. During the latter part of \{HS\} 11, the deep-water environment seems to be determined by strongly increased supply of organic matter, potentially explaining the decoupling of benthic δ13C and Mg/Ca records of earlier studies as a phytodetritus effect on the carbon isotope signal. However, the presence of a warm, nutrient-rich and poorly oxygenated water-mass cannot be ruled out. With the inception of interglacial \{MIS\} 5e trophic conditions are reduced and ventilation by \{NEADW\} increases.