Iridium abundance measurements across bio-event horizons in the fossil record [electronic resource].
- Washington, D.C : United States. Dept. of Energy. Office of Energy Research, 1989.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- Pages: (41 pages) : digital, PDF file
- Additional Creators:
- Los Alamos National Laboratory
United States. Department of Energy. Office of Energy Research
United States. National Aeronautics and Space Administration
United States. Department of Energy. Office of Scientific and Technical Information
- Geochemical measurements have been performed on thousands of rock samples collected across bio-event horizons using Instrumental Neutron Activation Analysis (INAA) for about 40 common and trace elements and radiochemical isolation procedures for Ir. On selected samples, Os, Pt and Au were also radiochemically determined. These studies have encompassed the time interval from the Precambrian-Cambrian transition to the Late Eocene impact (microspherule) horizons. Our early work strengthened the Alvarez impact hypothesis by finding the Ir (PGE) anomaly at the K-T boundary in continental sedimentary sequences. In collaborations with paleontologists, weak to moderately string Ir anomalies have been discovered at the Frasnian-Famennian boundary in Australia, in the Early Mississippian of Oklahoma, at the Mississipian-Pennsylvanian boundary of Oklahoma and Texas, and in the Late Cenomanian throughout the western interior of North America and on the south coast of England to date. We have found no compelling evidence for an impact related cause for these anomalies although PGE impact signatures in the two Late Cenomanian anomalies could be masked by the strong terrestrial mafic to ultramafic overprint. Thus far, our evidence for extinction events older than the terminal Cretaceous does not support recent hypotheses which suggest that impacts from cyclic swarms of comets in the inner Solar system were responsible for the periodic mass extinctions. 50 refs., 7 figs., 3 tabs.
- Published through SciTech Connect.
Snowbird conference on global catastrophies in earth history, Snowbird, UT (USA), 20-23 Oct 1989.
Attrep, M. Jr.; Orth, C.J.; Quintana, L.R.
- Funding Information:
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