Calcareous nannofossils and clastic sediments at the Cretaceous-Tertiary boundary, northeastern Mexico

Abstract

Research Article| March 01, 1996 Calcareous nannofossils and clastic sediments at the Cretaceous-Tertiary boundary, northeastern Mexico James J. Pospichal James J. Pospichal 1Department of Geology, Florida State University, Tallahassee, Florida 32306 Search for other works by this author on: GSW Google Scholar Author and Article Information James J. Pospichal 1Department of Geology, Florida State University, Tallahassee, Florida 32306 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1996) 24 (3): 255–258. https://doi.org/10.1130/0091-7613(1996)024<0255:CNACSA>2.3.CO;2 Article history First Online: 02 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 James J. Pospichal; Calcareous nannofossils and clastic sediments at the Cretaceous-Tertiary boundary, northeastern Mexico. Geology 1996;; 24 (3): 255–258. doi: https://doi.org/10.1130/0091-7613(1996)024<0255:CNACSA>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 SocietyGeology Search Advanced Search Abstract A quantitative analysis of calcareous nannofossil assemblages on the Cretaceous-Tertiary (K-T) boundary of the Mimbral and Mulato outcrops of northeast Mexico indicates that the sections are biostratigraphically complete across the boundary and that there is a prominent spherule-bearing clastic unit located precisely at the K-T boundary. The sections consist of uppermost Maastrichtian (Micula prinsii Zone) marly limestones of the Mendez Formation and marlstones of the lower Paleocene (Zone NP1) Velasco Formation separated by a distinct, 1–3-m-thick sandstone unit that has a basal spherule-bearing layer. The origin of this clastic unit and the time of deposition relative to the K-T mass extinctions have been the subjects of much controversy. Some workers attribute this unit to rapid tsunami-induced deposition triggered by the nearby Chicxulub impact, and others consider it a turbidite deposited at some time prior to the K-T mass extinctions. Cretaceous nannofossils abruptly decrease in abundance at the base of the spherule bed and only rare to few reworked specimens are present in the clastic unit and in the basal Velasco Formation. Survivors and Tertiary species are common above the clastic unit. Cretaceous nannoplankton show no evidence of recovery after deposition of the clastic unit, which indicates that extinctions probably occurred correlative with the deposition of the clastic unit and in association with the Chicxulub impact. 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.