Research Article| November 01, 1989 Extended period of extinctions across the Cretaceous /Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories GERTA KELLER GERTA KELLER 1Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08544 Search for other works by this author on: GSW Google Scholar Author and Article Information GERTA KELLER 1Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08544 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1989) 101 (11): 1408–1419. https://doi.org/10.1130/0016-7606(1989)101<1408:EPOEAT>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation GERTA KELLER; Extended period of extinctions across the Cretaceous /Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories. GSA Bulletin 1989;; 101 (11): 1408–1419. doi: https://doi.org/10.1130/0016-7606(1989)101<1408:EPOEAT>2.3.CO;2 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 The extinction of planktonic foraminiferal species across the Cretaceous/Tertiary (K/T) boundary has been examined in continental-shelf sections at El Kef, Tunisia, and Brazos River, Texas. These sections are considered to contain the most complete boundary transition record known to date. In both sections, an extended period of species extinctions spans from about 300,000 yr below to about 200,000-300,000 yr above the K/T boundary. Distinct episodes of accelerated extinctions occur below the boundary and about 50,000 yr above the boundary. At El Kef, only 26% of the species extinctions appear directly associated with the K/T boundary and iridium anomaly. At Brazos River, no species extinctions or measurable faunal changes appear directly associated with the K/T boundary and iridium anomaly. Species extinctions selectively affect large, ornate, tropical to subtropical species first and small, primitive, nonornate, subtropical to temperate species last. This pattern of species extinction is likely caused by increased ecological stresses as a result of a late Maastrichtian sea-level regression and global cooling. The extended period of species extinctions and absence of extinctions at the K/T boundary at Brazos River is not entirely compatible with either impact or volcanism theories. Perhaps, multiple unrelated causes should be considered, including a sea-level regression, global cooling, a K/T boundary impact of limited extent, and extensive volcanism. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.