Isotope Signature of calcareous Organisms from upper and Lower carbonate mound sediments 2

• Applicant: Professor Dr. Wolf-Christian Dullo
• Subject Area: Palaeontology
• Term: from 2007 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 49066122

, Cold-water coral mounds or carbonate mounds are known to occur widespread within the Porcupine Seabight. Sediment cores from gravity corer and especially drill cores from ICDP Expedition 307 at Challenger Mound indicate the recurring and abrupt occurring changes of carbonate mound growth. Geochemical signals in biogenic tests of planctonic and benthic foraminifers, as well as in skeletons of cold-water corals will allow us to understand the mechanisms of these changes. Stable isotope signature of benthic foraminifera (δ18O, δ13O) from the mound initiation shows a significant change to values characteristic for the water masses derived from the Mediterranean Sea (Mediterranean Outflow). Paleotemperatures derived from Sr/Ca from coral skeletons indicate optimum conditions of growth fort these biota. We speculate that the density envelope of σө= 27.35 - 27.65 kg/m3 characteristic for the ambient seawater of present day cold water coral growth played also an important role in the past. To reconstruct and to better understand these changes between „shut on" and „shut off“ conditions in mound growth we aim to date more samples from lODP-Kem 1317C to close thc existing gap in information. Since conventional U/Th methods are limited to the upper portions of the core (about 350 ka), we shall also apply precise 234U/238U (234U excess decay) and 87Sr/86Sr (radiogenic Sr evolution in the ocean), to better constrain the growth modcl and to reconstmct the encountered hiatuses. The geochronological aspect is a central part for the last year, to reconstmct the mound shaping mechanisms in relation to paleoenvironmental, to paleoclimatotological and to palcoceanographical conditions. The geochemical work will focus on thc analysis of isotopes in foraminifera and element rations in corals to reconstruct paleotemperatures and paleosalinilies, which in combination may provide data on paleodensities of sea water.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Bereich Infrastruktur - "International Ocean Discovery Program" (IODP)
• International Connection: Belgium
• Participating Persons: Professor Dr. Anton Eisenhauer; Dr. Volker Liebetrau (†); Dr. Andres Rüggeberg