| Abstract: | A newly discovered Cretaceous-Tertiary (K-T) boundary locality in the western Powder River basin, Wyoming, is characterized by a palynologically defined extinction horizon, a fern-spore abundance anomaly, a strong iridium anomaly, and shock-metamorphosed quartz grains. Detailed microstratigraphic analyses show that about one third of the palynoflora (mostly angiosperm pollen) disappeared abruptly, placing the K-T boundary within a distinctive, 1- to 2-cm-thick claystone layer. Shocked quartz grains are concentrated at the top of this layer, and although fern-spore and iridium concentrations are high in this layer, they reach their maximum concentrations in a 2-cm-thick carbonaceous claystone that overlies the boundary claystone layer. The evidence supports the theory that the K-T boundary event was associated with the impact of an extraterrestrial body or bodies. Palynological analyses of samples from the K-T boundary interval document extensive changes in the flora that resulted from the boundary event. The palynologically and geochemically defined K-T boundary provides a unique time-line of use in regional basin analysis. ?? 1992. |
| Genre: | Article |
| ProdID: | 70017160 |
| Citation Author: | Nichols, D. J.; Brown, J. L.; Attrep, Jr. , M.; Orth, C. J. |
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| Citation End Page: | 30 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Cretaceous Research |
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| Citation Number Of Pages: | 28 |
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| Citation Search Results Text: | A new Cretaceous-Tertiary boundary locality in the western powder River basin, Wyoming: biological and geological implications; 1992; Article; Journal; Cretaceous Research; Nichols, D. J.; Brown, J. L.; Attrep, Jr. , M.; Orth, C. J. |
| Citation Start Page: | 3 |
| Citation Volume: | 13 |
| Citation Year: | 1992 |
| Type: | citation/reference |
| Text: | A new Cretaceous-Tertiary boundary locality in the western powder River basin, Wyoming: biological and geological implications; 1992; Article; Journal; Cretaceous Research; Nichols, D. J.; Brown, J. L.; Attrep, Jr. , M.; Orth, C. J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1992 00:00 -0600 |
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