georefid:2011-007988SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-07-06T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1130/G31195.12010-01-01publicationgeorefid:2011-007988doi:10.1130/G31195.1Jimenez Berrocoso, AlvaroUniversity of Missouri, Department of Geological Sciences, Columbia, MO, United StatesauthorMacLeod, Kenneth G.University of Florida, United StatesauthorMartin, Ellen E.authorBourbon, ElodieauthorLondono, Carolina IsazaauthorBasak, ChandranathauthorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyGeology (Boulder)38 (12)1111-1114Neodymium isotopes of fish debris from two sites on Demerara Rise, spanning approximately 4.5 m.y. of deposition from the early Cenomanian to just before ocean anoxic event 2 (OAE2) (Cenomanian-Turonian transition), suggest a circulation-controlled nutrient trap in intermediate waters of the western tropical North Atlantic that could explain continuous deposition of organic-rich black shales for as many as approximately 15 m.y. (Cenomanian-early Santonian). Unusually low Nd isotopic data (epsilon (sub Nd(t)) approximately -11 to approximately -16) on Demerara Rise during the Cenomanian are confirmed, but the shallower site generally exhibits higher and more variable values. A scenario in which southwest-flowing Tethyan and/or North Atlantic waters overrode warm, saline Demerara bottom water explains the isotopic differences between sites and could create a dynamic nutrient trap controlled by circulation patterns in the absence of topographic barriers. Nutrient trapping, in turn, would explain the approximately 15 m.y. deposition of black shales through positive feedbacks between low oxygen and nutrient-rich bottom waters, efficient phosphate recycling, transport of nutrients to the surface, high productivity, and organic carbon export to the seafloor. This nutrient trap and the correlation seen previously between high Nd and organic carbon isotopic values during OAE2 on Demerara Rise suggest that physical oceanographic changes could be components of OAE2, one of the largest perturbations to the global carbon cycle in the past 150 m.y.completedStratigraphyIsotope geochemistryanaerobic environmentAtlantic Oceanblack shaleC-13/C-12carbonCenomanianclastic rocksCretaceousDemerara Risedepositional environmentEquatorial Atlanticgeochemistryisotope ratiosisotopesLeg 207marine environmentMesozoicmetalsneodymiumNorth AtlanticNorthwest AtlanticnutrientsOAE 2Ocean Drilling Programoceanic anoxic eventsODP Site 1258ODP Site 1260organic compoundspaleo-oceanographypaleocirculationrare earthsSantoniansedimentary rocksSenonianstable isotopestropical environmentUpper CretaceousWest Atlanticurn:org.iodp:exp:207urnlargerWorkCitationcampaignurn:org.iodp:exp:207:site:1258urnlargerWorkCitationstudyurn:org.iodp:exp:207urnlargerWorkCitationcampaignurn:org.iodp:exp:207:site:1260urnlargerWorkCitationstudyurn:org.iodp:exp:207urnlargerWorkCitationcampaignEnglishgeoscientificInformation-54.4400-54.33009.16009.2600With GSA Data Repository Item 2010301