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Title: Impact theory of mass extinctions and the invertebrate fossil record

There is much evidence that the Cretaceous-Tertiary boundary was marked by a massive meteorite impact. Theoretical consideration of the consequences of such an impact predicts sharp extinctions in many groups of animals precisely at the boundary. Paleontological data clearly show gradual declines in diversity over the last 1 to 10 million years in various invertebrate groups. Reexamination of data from careful studies of the best sections shows that, in addition to undergoing the decline, four groups (ammonites, cheilostomate bryozoans, brachiopods, and bivalves) were affected by sudden truncations precisely at the iridium anomaly that marks the boundary. The paleontological record thus bears witness to terminal-Cretaceous extinctions on two time scales: a slow decline unrelated to the impact and a sharp truncation synchronous with and probably caused by the impact. 50 references, 4 figures.
Authors:
; ; ; ; ;
Publication Date:
OSTI Identifier:
5808167
Resource Type:
Journal Article
Resource Relation:
Journal Name: Science (Washington, D.C.); (United States); Journal Volume: 223:4641
Research Org:
Univ. of California, Berkeley
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; INVERTEBRATES; BIOLOGICAL EXTINCTION; METEORITES; ENVIRONMENTAL IMPACTS; BOUNDARY LAYERS; CRETACEOUS PERIOD; FOSSILS; IRIDIUM; PALEONTOLOGY; SPECIES DIVERSITY; TERTIARY PERIOD; ANIMALS; CENOZOIC ERA; ELEMENTS; GEOLOGIC AGES; LAYERS; MESOZOIC ERA; METALS; PLATINUM METALS; TRANSITION ELEMENTS 510100* -- Environment, Terrestrial-- Basic Studies-- (-1989); 580100 -- Geology & Hydrology-- (-1989)