Paleoenvironmental reconstruction of Challenger Mound initiation in the Porcupine Seabight, NE Atlantic

Bottom currents transporting intermediate water masses of southern origin (Mediterranean and Bay of Biscay) enhanced at 2.6 Ma supporting first coral settlements with the INHG. The benthic δ13C and the sortable silt records indicate that the early Pleistocene hydrodynamic regime was characterized by weaker current intensities associated with vertical movements of MOW or its replacement by SCW at intermediate depth. After these sluggish phases enhanced MOW flow dominated again and led to stronger current intensities and most probably sediment erosion on Challenger Mound. Erosion in combination with early diagenetic (oxidation) processes overprinted the sediment layers as indicated by dissolved coral skeletons, the increase in Ca-content and sediment density, minimum δ13Cplanktonic values, as well as the occurrence of gypsum and pyrite, implying a careful evaluation of original and overprinted geochemical signals. We conclude that the Challenger Mound development was already influenced by short-term variability of water masses from southern origin and possible erosional events comparable to the late Pleistocene setting.