HR: 0800h
AN: B31C-0507    [Abstracts]
TI: Carbonate mound evolution and coral diagenesis viewed by U-series dating of deep water corals
AU: Frank, N
EM: Norbert.Frank@cea.fr
AF: Laboratoire des Sciences du Climat et de L'Environnement - IPSL/CEA-CNRS-UVSQ, Bat. 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: Ricard, E
AF: Laboratoire des Sciences du Climat et de L'Environnement - IPSL/CEA-CNRS-UVSQ, Bat. 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: * Blamart, D
EM: Dominique.Blamart@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de L'Environnement - IPSL/CEA-CNRS-UVSQ, Bat. 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: van der Land, C
EM: cland@nioz.nl
AF: Royal Netherlands Institute for Sea Research, P.O. Box 59, AB den Burg, Texel, NL-1790, Netherlands
AU: Colin, C
AF: Laboratoire des Interactions et Dynamique des Environnements de Surface, University Paris XI, Bat. 504 Geologie, Orsay, 91405, France
AU: Foubert, A
AF: Renard Center of Marine Geology, Gent University, Krijgslaan 281 s8, Gent, B-9000, Belgium
AU: van Rooij, D
AF: Renard Center of Marine Geology, Gent University, Krijgslaan 281 s8, Gent, B-9000, Belgium
AU: van Weering, T
AF: Royal Netherlands Institute for Sea Research, P.O. Box 59, AB den Burg, Texel, NL-1790, Netherlands
AB: U-series dating of constructional deep sea corals is a powerful tool to reconstruct the evolution of carbonate mound sediments driven by coral growth, sediment trapping and diagenesis. Here we have investigated in great detail the time framework of constructional corals such as L. pertusa and M. oculata on 5 different mounds of the eastern North Atlantic (on Rockall Bank and in Porcupine Seabight) taken at variable depth and location (610 to 880m water depth). Periods favorable for coral growth are the Holocene and prior interglacials such as marine isotope stage 5 and 7, while glacial coral growth seems inhibited or extremely reduced. Coral development is almost continuous throughout the Holocene since mound re-colonization about 10,500 years ago. Mound accumulation rates vary between 20 and 220 cm/kyr determined from the coral age - depth relationship in each core. Those changes are most likely driven by changes between horizontal and vertical mound accumulation, food supply and ocean circulation. In addition, coral dating allowed to identify an important erosional event recorded in core MD01-2455G from Rockall Bank. Here a 1m thick sediment layer containing ancient corals likely from the start of Holocene re-colonization was displaced (collapsed) from further upslope on top of younger corals of ~2500 to 3000 years age. Prior to the initiation of coral growth diagenesis occurred frequently resulting in (1) the construction of so called carbonate hardgrounds and/or (2) the dissolution of the pre-Holocene coral framework. Solely, the deepest selected core in Porcupine Seabight (MD01-2463G at 880m depth) reveals coral re-colonization on an undisturbed ancient reef structure that dates back to 250,000 years. Diagenesis of earlier coral reef generations leading to coral dissolution leads to a loss of magnetic susceptibility and open system behavior of the coral skeletons with respect to U-series dating. While the processes causing such diagenetic layers are barely understood the disappearance of the magnetic susceptibility can be used to trace such phenomena and a conserved magnetic susceptibility allows sampling of well preserved corals.
DE: 1115 Radioisotope geochronology
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting