| 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. |
| Genre: | Article |
| ProdID: | 70014029 |
| Citation Author: | Bohor, B. F.; Foord, E. E.; Modreski, P. J.; Triplehorn, D. M. |
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| Citation End Page: | 869 |
| Citation Issue: | 4648 |
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| Citation Language: | English |
| Citation Larger Work Title: | Science |
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| Citation Number Of Pages: | 3 |
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| Citation Search Results Text: | Mineralogic evidence for an impact event at the cretaceous-tertiary boundary; 1984; Article; Journal; Science; Bohor, B. F.; Foord, E. E.; Modreski, P. J.; Triplehorn, D. M. |
| Citation Start Page: | 867 |
| Citation Volume: | 224 |
| Citation Year: | 1984 |
| Type: | citation/reference |
| Text: | Mineralogic evidence for an impact event at the cretaceous-tertiary boundary; 1984; Article; Journal; Science; Bohor, B. F.; Foord, E. E.; Modreski, P. J.; Triplehorn, D. M. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1984 00:00 -0600 |
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