| Abstract: | Eocene volcanic flow and dike rocks from the Beringian margin have arc characteristics, implying a convergent history for this region during the early Tertiary. Chemical and mineralogical compositions are similar to those of modern Aleutian-arc lavas. They also resemble volcanic-arc compositions from western mainland Alaska, although greater chemical diversity and a stronger continental influence are observed in the Alaskan mainland rocks. Early Eocene ages of 54.4-50.2 Ma for the Beringian samples are well constrained by conventional K-Ar ages of nine plagioclase separates and by concordant 40Ar/39Ar incremental heating and total-fusion experiments. A concordant U-Pb zircon age of 53 Ma for the quartz-diorite dike is in good agreement with the K-Ar data. Plate motion studies of the North Pacific Ocean indicate more northerly directed subduction prior to the Tertiary and a continuous belt of arc-type volcanism extending from Siberia, along the Beringian margin, into mainland Alaska. Around 56 Ma (chron 25-24), subduction changed to a more westerly direction and subduction-related volcanism ceased for most of mainland Alaska. The increasingly oblique angle of convergence should have ended subduction along the Beringian margin as well. However, consistent ages of 54-50 Ma indicate a final pulse in arc-type magmatism during this period of plate adjustment. -from Authors |
| Genre: | Article |
| ProdID: | 70015232 |
| Citation Author: | Davis, A. S.; Pickthorn, L. -B. G.; Vallier, T. L.; Marlow, M. S. |
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| Citation End Page: | 1490 |
| Citation Issue: | 7 |
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| Citation Language: | English |
| Citation Larger Work Title: | Canadian Journal of Earth Sciences |
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| Citation Number Of Pages: | 17 |
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| Citation Search Results Text: | Petrology and age of volcanic-arc rocks from the continental margin of the Bering Sea: implications for Early Eocene relocation of plate boundaries; 1989; Article; Journal; Canadian Journal of Earth Sciences; Davis, A. S.; Pickthorn, L. -B. G.; Vallier, T. L.; Marlow, M. S. |
| Citation Start Page: | 1474 |
| Citation Volume: | 26 |
| Citation Year: | 1989 |
| Type: | citation/reference |
| Text: | Petrology and age of volcanic-arc rocks from the continental margin of the Bering Sea: implications for Early Eocene relocation of plate boundaries; 1989; Article; Journal; Canadian Journal of Earth Sciences; Davis, A. S.; Pickthorn, L. -B. G.; Vallier, T. L.; Marlow, M. S. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1989 00:00 -0600 |
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