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Extraterrestrial Cause for the Cretaceous-Tertiary Extinction
A hypothesis is suggested which accounts for the extinctions and the iridium observations, and the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other.
Iridium Anomalies of Late Eocene Age at Massignano (Italy), and ODP Site 689B (Maud Rise, Antarctic)
Iridium anomalies of Late Eocene age are here reported in sequences from northern Italy and Weddell Sea, Antarctic. We have analyzed 270 samples of marly limestones from the Eocene/Oligocene boundary…
Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition
Sand-size spheroids of K-feldspar in the Cretaceous-Tertiary (C-T) boundary clay at Caravaca, southern Spain, were interpreted by Smit and Klaver as having solidified from a melt resulting from the…
Iridium Anomaly Approximately Synchronous with Terminal Eocene Extinctions
The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago, and other workers have deduced that the microtekkites are part of the North American strewn tektite field, which is dated at about34 million years before present.
Special Studies: The Obsidian Trade at Isla Cerritos, Yucatán, Mexico
AbstractProvenience analysis of a small sample of obsidian artifacts from Isla Cerritos, a Terminal Classic/Early Postclassic Itza trading port on the north coast of Yucatan, indicates a wide range…
Ecuadorian Obsidian Sources Used for Artifact Production and Methods for Provenience Assignments
- F. Asaro, E. Salazar, H. Michel, R. Burger, F. Stross
- GeologyLatin American Antiquity
- 1 September 1994
A study by neutron activation analysis and X-ray fluorescence measurements of 116 Ecuadorian obsidian artifacts as well as primary and secondary source samples has shown that the material originated…
Current status of the impact theory for the terminal Cretaceous extinction
Iridium is depleted in the earth's crust relative to its normal solar system abundance. Several hundred measurements by at least seven laboratories have disclosed an iridium abundance anomaly at the…
Impact Theory of Mass Extinctions and the Invertebrate Fossil Record
- W. Alvarez, E. Kauffman, F. Surlyk, L. W. Alvarez, F. Asaro, H. Michel
- Environmental Science, GeographyScience
- 16 March 1984
The paleontological record 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.
The End of the Cretaceous: Sharp Boundary or Gradual Transition?
Evidence indicates that the Cretaceous-Tertiary boundary is very sharp, and, within the limits of resolution, it is apparently synchronous at the various boundary localities. Arguments to the…
The Precursor of the Cretaceous-Tertiary Boundary Clays at Stevns Klint, Denmark, and DSDP Hole 465A
The mixed-layer smectite-illite from the interval 118 to 120 centimeters in the zone of high iridium abundance has a very low rare earth element content; the negative cerium anomaly indicates formation in the marine environment.