Origin,Growth and demise of the cold-water coral mound Challenger (IODP Site 1317)

• Main Author: Raddatz, Jacek
• Other Authors: Dullo, Wolf-Christian, Eisenhauer, Anton
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2011
• Subjects: thesis; ddc:550; Carbonate mounds; Cold-water corals; North Atlantic; Porcupine Seabight
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-75153; https://macau.uni-kiel.de/receive/diss_mods_00007515; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00004095/Diss_Raddatz2011.pdf

The Integrated Ocean Drilling Program (IODP) Expedition 307 was proposed to obtain evidence for understanding the origin and evolution of a 155 m high deepwater carbonate mound in the Porcupine Seabight. The major aim of this study is the reconstruction of environmental parameters using well-developed paleoceanographic proxies derived from calcareous tests and skeletons of benthic organisms based on sediment cores from this expedition. In particular, this study uses different archives such as scleractinian cold-water corals and calcitic foraminifers. The second chapter (published in Marine Geology 2011) reports on a high-resolution record of the mound base. Stable oxygen and carbon isotopes measured in several benthic and planktonic foraminifers as well as sortable silt analyses document the start-up phase of coral growth. Mound initiation and further development coincide with the intensification of Mediterranean Outflow Water (MOW) characterized by oceanographic conditions favourable for rapid cold-water coral growth. Furthermore excursions in foraminiferal δ13C values and increased flow conditions indicate erosional intervals, which overprinted probably diagenetically the original geochemical signals. The third chapter (to be submitted to Geology), also based on sediments from the mound base, shows that these ecosystems only thrive under specific oceanographic conditions. Based on core material, not only from Challenger Mound (IODP Expedition 307) but also from the Propeller Mound, we reconstructed paleo-seawater densities from oxygen isotope ratios in benthic foraminifera. Results clearly indicate results demonstrate that cold-water coral mound development occurred when a density window of sigma-theta (σΘ) = 27.35–27.55 kg m-3 was present in the ambient bottom water. Therefore we conclude that seawater density is reflecting one of the major controlling factors favoring mound growth and highlights the sensitivity of these ecosystems to environmental changes. The fourth chapter (submitted to Earth Planetary ...