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Osmium-187/osmium-186 in manganese nodules and the Cretaceous-Tertiary boundary

Journal Article · · Science (Washington, D.C.); (United States)
;
As a result of the radioactive decay of rhenium-187 (4.6 x 10/sup 10/ years) the osmium-187/osmium-186 ratio changes in planetary systems as a function of time and the rhenium-187/osmium-186 ratio. For a value of the rhenium-187/osmium-186 ratio of about 3.2, typical of meteorites and the earth's mantle, the present-day osmium-187/osmium-186 ratio is about 1. The earth's continental crust has an estimated rhenium-187/osmium-186 ratio of about 400, so that for a mean age of the continent of 2 x 10/sup 9/ years, a present-day osmium-187/osmium-186 ratio of about 10 is expected. Marine manganese nodules show values (6 to 8.4) compatible with this expectation if allowance for a 25 percent mantle osmium supply to the oceans is allowed. The Cretaceous-Tertiary boundary iridium-rich layer in the marine section at Stevns Klint, Denmark, yields an osmium-187/osmium-186 ratio of 1.65, and the one in a continental section in the Raton Basin, Colorado, is 1.29. The simplest explanation is that these represent osmium imprints of predominantly meteoritic origin.
Research Organization:
Yale Univ., New Haven, CT
OSTI ID:
5314102
Journal Information:
Science (Washington, D.C.); (United States), Journal Name: Science (Washington, D.C.); (United States); ISSN SCIEA
Country of Publication:
United States
Language:
English

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Related Subjects

520301* -- Environment
Aquatic-- Radioactive Materials Monitoring & Transport-- Water-- (1987)
54 ENVIRONMENTAL SCIENCES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BOUNDARY LAYERS
COLORADO
CONTAMINATION
CONTINENTAL CRUST
DENMARK
EARTH CRUST
EUROPE
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION VIII
HALF-LIFE
HEAVY NUCLEI
ISOTOPES
LAYERS
METEORITES
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
ORIGIN
OSMIUM 186
OSMIUM 187
OSMIUM ISOTOPES
QUANTITY RATIO
RADIOISOTOPES
RHENIUM 187
RHENIUM ISOTOPES
SCANDINAVIA
STABLE ISOTOPES
USA
WESTERN EUROPE
YEARS LIVING RADIOISOTOPES