georefid:2007-014828SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1130/B25955.12007-01-01publicationgeorefid:2007-014828doi:10.1130/B25955.1MacLeod, Kenneth G.University of Missouri, Department of Geological Sciences, Columbia, MO, United StatesauthorWhitney, Donna L.University of Minnesota, United StatesauthorHuber, Brian T.Smithsonian National Museum of Natural History, United StatesauthorKoeberl, ChristianUniversity of Vienna, AustriaauthorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyGeological Society of America Bulletin119 (1-2)101-115Ocean Drilling Program (ODP) Leg 207, on the Demerara Rise in the western tropical North Atlantic, recovered multiple Cretaceous-Paleogene boundary sections containing an ejecta layer. Sedimentological, geochemical, and paleontological changes across the boundary closely match patterns expected for a mass extinction caused by a single impact. A normally graded, approximately 2-cm-thick bed of spherules that is interpreted as a primary air-fall deposit of impact ejecta occurs between sediments of the highest Cretaceous Plummerita hantkeninoides foraminiferal zone and the lowest Paleogene P0 foraminiferal zone. There are no other spherule layers in the section. In addition to extinction of Cretaceous taxa, foraminiferal abundance drops from abundant to rare across the boundary. Ir concentrations reach a maximum of approximately 1.5 ppb at the top of the spherule bed, and the Ir anomaly is associated with enrichment in other siderophile elements. We attribute the unusually well-preserved and relatively simple stratigraphy to the fact that Demerara Rise was close enough ( approximately 4500 km) to the Chicxulub impact site to receive approximately 2 cm of ejecta, yet was far enough away (and perhaps sheltered by the curve of northern South America) to have been relatively unaffected by impact-induced waves.completedStratigraphyAtlantic OceanbiostratigraphybiozonesCenozoicChicxulub Craterclastic rocksclaystoneCretaceousDanianDemerara RiseejectaEquatorial Atlanticfaunal listForaminiferageochemical anomaliesgeochemistryimpactsInvertebratairidiumK-T boundaryLeg 207lower Paleocenemarine sedimentsmass extinctionsMesozoicmetalsmicrofossilsNorth AtlanticNorthwest AtlanticOcean Drilling ProgramODP Site 1259PaleocenePaleogeneplanktonic taxaplatinum groupPlummerita hantkeninoidesProtistarare earthssedimentary rockssedimentssiderophile elementsspherulesstratigraphic boundaryTertiaryUpper CretaceousX-ray dataurn:org.iodp:exp:207urnlargerWorkCitationcampaignurn:org.iodp:exp:207:site:1259urnlargerWorkCitationstudyurn:org.iodp:exp:207urnlargerWorkCitationcampaignEnglishgeoscientificInformation-54.1200-54.12009.18009.1800