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Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary
Abstract
A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.
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Citations
Cited by
THE GLOBAL STRATIGRAPHY OF THE CRETACEOUS-TERTIARY BOUNDARY IMPACT EJECTA
Smit, J. (1999) · Annual Review of Earth and Planetary Sciences · doi:10.1146/annurev.earth.27.1.75 · Cited by 466
ORIGINS OF THE GENETIC CODE: The Escaped Triplet Theory
Yarus, M., Caporaso, J. G., & Knight, R. (2005) · Annual Review of Biochemistry · doi:10.1146/annurev.biochem.74.082803.133119 · Cited by 166
O'Keefe, J. D., & Ahrens, T. J. (1989) · Nature · doi:10.1038/338247a0 · Cited by 158
Vredefort, Sudbury, Chicxulub: Three of a Kind?
Grieve, R., & Therriault, A. (2000) · Annual Review of Earth and Planetary Sciences · doi:10.1146/annurev.earth.28.1.305 · Cited by 133
Observations at terrestrial impact structures: Their utility in constraining crater formation
Grieve, R. A. F., & Therriault, A. M. (2004) · Meteoritics & Planetary Science · doi:10.1111/j.1945-5100.2004.tb00336.x · Cited by 60
Metadata
- Authors
- Bohor, B. F., Foord, E. E., Modreski, P. J., & Triplehorn, D. M.
- Venue
- Science
- Published
- 1984-05-25
- Volume
- 224
- Issue
- 4651
- Pages
- 867-869
- ISSN
- 0036-8075 (ISSN-L)
- 1095-9203
- OpenAlex
- W2038487387
- Cited by
- 307
- References
- 0
- FWCI
- 33.89
- Type
- journal article
- Language
- en
- Open access
- closed
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- Bohor, B. F., Foord, E. E., Modreski, P. J., & Triplehorn, D. M. (1984). Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary. Science. https://doi.org/10.1126/science.224.4651.867
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Contains information from the Semantic Scholar Academic Graph Datasets, made available under the ODC Attribution License (ODC-BY 1.0).
Semantic Scholar’s data is described in: Kinney, R., et al. (2023). The Semantic Scholar Open Data Platform. arXiv:2301.10140.
