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Title: Iridium abundance measurements across bio-event horizons in the fossil record

Abstract

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 inmore » the inner Solar system were responsible for the periodic mass extinctions. 50 refs., 7 figs., 3 tabs.« less

Authors:
; ;  [1]
  1. Los Alamos National Lab., NM (USA)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
DOE/ER; National Aeronautic and Space Administration (NASA)
OSTI Identifier:
5584069
Report Number(s):
LA-UR-89-354; CONF-891065-2
ON: DE89007752
DOE Contract Number:  
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Snowbird conference on global catastrophies in earth history, Snowbird, UT (USA), 20-23 Oct 1989
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; BIOLOGICAL EXTINCTION; VALIDATION; IRIDIUM; DETECTION; ROCKS; GEOCHEMISTRY; CLIMATE MODELS; COLLISIONS; COMETS; ENVIRONMENTAL EFFECTS; GEOCHEMICAL SURVEYS; MODIFICATIONS; RADIOCHEMICAL ANALYSIS; SPECIES DIVERSITY; CHEMICAL ANALYSIS; CHEMISTRY; ELEMENTS; MATHEMATICAL MODELS; METALS; PLATINUM METALS; QUANTITATIVE CHEMICAL ANALYSIS; SURVEYS; TESTING; TRANSITION ELEMENTS; 580100* - Geology & Hydrology- (-1989)

Citation Formats

Orth, C J, Attrep, M Jr, and Quintana, L R. Iridium abundance measurements across bio-event horizons in the fossil record. United States: N. p., 1989. Web.
Orth, C J, Attrep, M Jr, & Quintana, L R. Iridium abundance measurements across bio-event horizons in the fossil record. United States.
Orth, C J, Attrep, M Jr, and Quintana, L R. Sun . "Iridium abundance measurements across bio-event horizons in the fossil record". United States. https://www.osti.gov/servlets/purl/5584069.
@article{osti_5584069,
title = {Iridium abundance measurements across bio-event horizons in the fossil record},
author = {Orth, C J and Attrep, M Jr and Quintana, L R},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/5584069}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {1}
}

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