The importance of the terrigenous fraction within a cold-water coral mound: A case study

• Published in: Marine Geology
• Main Authors: Pirlet, Hans, Colin, Christophe, Thierens, Mieke, Latruwe, Kris, Van Rooij, David, Foubert, Anneleen, Frank, Norbert, Blamart, Dominique, Huvenne, Veerle A.I., Swennen, Rudy, Vanhaecke, Frank, Henriet, Jean-Pierre
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2011
• Subjects: Canada; Greenland; Porcupine Seabight; Iceland
• Online Access: http://nora.nerc.ac.uk/id/eprint/287629/

In the nineties, cold-water coral mounds were discovered in the Porcupine Seabight (NE Atlantic, west of Ireland). A decade later, this discovery led to the drilling of the entire Challenger cold-water coral mound (Eastern slope, Porcupine Seabight) during IODP Expedition 307. As more than 50% of the sediment within Challenger Mound consists of terrigenous material, the terrigenous component is equally important for the build-up of the mound as the framework-building corals. Moreover, the terrigenous fraction contains important information on the dynamics and the conditions of the depositional environment during mound development. In this study, the first in-depth investigation of the terrigenous sediment fraction of a cold-water coral mound is performed, combining clay mineralogy, sedimentology, petrography and Sr–Nd-isotopic analysis on a gravity core (MD01-2451G) collected at the top of Challenger Mound. Sr- and Nd-isotopic fingerprinting identifies Ireland as the main contributor of terrigenous material in Challenger Mound. Besides this, a variable input of volcanic material from the northern volcanic provinces (Iceland and/or the NW British Isles) is recognized in most of the samples. This volcanic material was most likely transported to Challenger Mound during cold climatic stages. In three samples, the isotopic ratios indicate a minor contribution of sediment deriving from the old cratons on Greenland, Scandinavia or Canada. The grain-size distributions of glacial sediments demonstrate that ice-rafted debris was deposited with little or no sorting, indicating a slow bottom-current regime. In contrast, interglacial intervals contain strongly current-sorted sediments, including reworked glacio-marine grains. The micro textures of the quartz-sand grains confirm the presence of grains transported by icebergs in interglacial intervals. These observations highlight the role of ice-rafting as an important transport mechanism of terrigenous material towards the mound during the Late Quaternary. Furthermore, ...