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Iridium abundance maxima in the Upper Cenomanian extinction intervalTwo iridium abundance peaks, both 0.11 ppb (whole-rock basis) over a local background of 0.017 ppb, have been found in Middle Cretaceous marine rocks near Pueblo, Colorado. They occur just below the 92-million-year-old Cenomanian-Turonian (C-T) stage boundary. No other peaks were found in 45 meters of strata (about 2.5 million years of deposition) above and below the boundary interval. The broad lower peak straddles the first in a series of extinctions of benthic and nektonic macrobiota which comprise the C-T extinction event. The sharp upper peak occurs stratigraphically about 1.2 meters above the lower peak. The excess Ir might be from meteoroid impacts.
Document ID
19880044563
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Orth, C. J.
(Los Alamos National Lab. NM, United States)
Attrep, M., Jr.
(Los Alamos National Lab. NM, United States)
Mao, X. Y.
(Los Alamos National Laboratory NM, United States)
Kauffman, E. G.
(Los Alamos National Lab. NM, United States)
Diner, R.
(Colorado, University Boulder, United States)
Date Acquired
August 13, 2013
Publication Date
April 1, 1988
Publication Information
Publication: Geophysical Research Letters
Volume: 15
ISSN: 0094-8276
Subject Category
Geophysics
Accession Number
88A31790
Distribution Limits
Public
Copyright
Other

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