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

• Main Authors: Raddatz, Jacek, Rüggeberg, Andres, Margreth, Stephan, Dullo, Wolf-Christian, IODP Expedition 307 Scientific Party
• Language: English
• Published: 2011
• Subjects: Porcupine Seabight; Antarc*; Antarctica; North Atlantic
• Online Access: http://doc.rero.ch/record/27032/files/mar_prc.pdf

The understanding of the paleoenvironment during initiation and early development of deep cold-water coral carbonate mounds in the NE Atlantic is currently a focus of international research. The Integrated Ocean Drilling Program (IODP) Expedition 307 drilled the 155 m high Challenger Mound in the Porcupine Seabight (SW off Ireland) in order to investigate for the first time sediments from the base of a giant carbonate mound. In this study we focus in high resolution on 12 m of sediments from Site 1317 encompassing the mound base. The mound initiation and start-up phase coincide with the intensification of the Northern Hemisphere Glaciation (INHG) at around 2.7 Ma. Further carbonate mound development seems to be strongly dependent on rapid changes in paleoceanographic and climatic conditions at the Pliocene–Pleistocene boundary, especially characterized and caused by the interaction of intermediate water masses, the Mediterranean Outflow Water (MOW), the Eastern North Atlantic Water (ENAW) and the influence of Southern Component Water (SCW). This study is based on well-established proxies such as δ¹⁸O and δ¹³C of planktonic ( Globigerina bulloides ) and benthic foraminifera ( Fontbotia wuellerstorfi , Discanomalina coronata , Lobatula lobatula , Lobatula antarctica , and Planulina ariminensis ) as well as grain size parameters to identify the paleoenvironmental and paleoecological setting favourable for the initial coral colonization on the mound. Stable oxygen and carbon isotope records of benthic foraminiferal species indicate that L. lobatula provides a reliable isotopic signature for paleoenvironmental reconstructions. In particular, δ¹⁸O values of L. lobatula indicate that initial mound growth started in a glacial mode with moderate excursions in δ¹⁸O values. Carbon isotope values of D. coronata are significantly offset compared to other epibenthic species. This offset may be related to vital effects. Bottom water temperatures, calculated using standard equations based on δ¹⁸O of foraminiferal tests, range ...