Distribution of noble metals across the Cretaceous/Tertiary boundary at Gubbio, Italy: Iridium variation as a constraint on the duration and nature of Cretaceous/Tertiary boundary events

Abstract

Research Article| January 01, 1988 Distribution of noble metals across the Cretaceous/Tertiary boundary at Gubbio, Italy: Iridium variation as a constraint on the duration and nature of Cretaceous/Tertiary boundary events James H. Crocket; James H. Crocket 1Department of Geology, McMaster University, Hamilton, Ontario L8S 4M1, Canada Search for other works by this author on: GSW Google Scholar Charles B. Officer; Charles B. Officer 2Earth Sciences Department, Dartmouth College, Hanover, New Hampshire 03755 Search for other works by this author on: GSW Google Scholar Forese C. Wezel; Forese C. Wezel 3Instituto di Geologia, Universita degli Studi, 61029 Urbino, Italy Search for other works by this author on: GSW Google Scholar Gary D. Johnson Gary D. Johnson 4Earth Sciences Department, Dartmouth College, Hanover, New Hampshire 03755 Search for other works by this author on: GSW Google Scholar Geology (1988) 16 (1): 77–80. https://doi.org/10.1130/0091-7613(1988)016<0077:DONMAT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation James H. Crocket, Charles B. Officer, Forese C. Wezel, Gary D. Johnson; Distribution of noble metals across the Cretaceous/Tertiary boundary at Gubbio, Italy: Iridium variation as a constraint on the duration and nature of Cretaceous/Tertiary boundary events. Geology 1988;; 16 (1): 77–80. doi: https://doi.org/10.1130/0091-7613(1988)016<0077:DONMAT>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 Iridium, Pd, Pt, and Au were determined in sections from the Bottaccione Gorge and Contessa Valley, Gubbio, Italy, by radiochemical neutron activation. Shales and limestones were sampled from 2.85 m above to 219 m below the Cretaceous/Tertiary (K/T) boundary. Metal enrichment was evaluated by comparing the boundary shale region with the lower part of the section (background). Iridium is concentrated by 63 times in the boundary shales in comparison with the background, whereas other metals are enriched by no more than 2.2 times. The enrichment of Ir is not confined to the boundary shales but extends approximately 2 m above and below this horizon. Within this Ir-rich region there are four distinct Ir maxima in addition to the major Ir enrichment in the K/T boundary shales. Iridium maxima are stratigraphically coincident with maxima in abundances of shocked minerals characteristic of explosive volcanism. Limestones are much lower in noble metals than shales, and their Ir contents in the K/T boundary region are largely accounted for by their minor clay mineral contents. The time represented by the 4 m of Ir-rich section is at least 3 x 105 yr, if published sedimentation rates are used. To sustain an increased Ir flux over this period and to account for the Ir distribution near the K/T boundary, intense volcanic activity is a preferred alternative to impact of extraterrestrial material. 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.