Impact and extinction in remarkably complete Cretaceous-Tertiary boundary sections from Demerara Rise, tropical western North Atlantic

Research Article| January 01, 2007 Impact and extinction in remarkably complete Cretaceous-Tertiary boundary sections from Demerara Rise, tropical western North Atlantic Kenneth G. MacLeod; Kenneth G. MacLeod 1Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA Search for other works by this author on: GSW Google Scholar Donna L. Whitney; Donna L. Whitney 2Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA Search for other works by this author on: GSW Google Scholar Brian T. Huber; Brian T. Huber 3Department of Paleobiology, Smithsonian National Museum of Natural History, Washington, DC 20013-7012, USA Search for other works by this author on: GSW Google Scholar Christian Koeberl Christian Koeberl 4Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (1-2): 101–115. https://doi.org/10.1130/B25955.1 Article history received: 19 Dec 2005 rev-recd: 29 Apr 2006 accepted: 01 Jul 2006 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kenneth G. MacLeod, Donna L. Whitney, Brian T. Huber, Christian Koeberl; Impact and extinction in remarkably complete Cretaceous-Tertiary boundary sections from Demerara Rise, tropical western North Atlantic. GSA Bulletin 2007;; 119 (1-2): 101–115. doi: https://doi.org/10.1130/B25955.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Ocean 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, ∼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 ∼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 (∼4500 km) to the Chicxulub impact site to receive ∼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. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.