| Abstract: | Apparent apatite fission-track ages from drill core penetrating basement on the flank of the Transcontinental Arch in northwestern Iowa range from 934 ?? 86 to 641 ?? 90 Ma. These ages, the oldest reported in North America, record at least two thermal events. The 934 Ma age, which is synchronous with KAr ages in the Grenville Province and many KAr whole-rock and RbSr isochron ages from the Lake Superior region, may document basement cooling caused by regional uplift and erosion of the crust. The remaining fission-track ages are products of a more recent thermal event, relative to the age of the samples, which raised temperatures into the zone of partial annealing. Heating may have occurred between the Middle Ordovician and Middle Cretaceous by burial of the basement with additional sediment. It is estimated that burial raised temperatures in the part of the basement sampled by the core to between 50 and 75??C. These temperature estimates imply paleogeothermal gradients of about 20??C/km, approximately two and one-half times present-day values, and burial of the basement by an additional 2-3 km of sediment. ?? 1986. |
| Genre: | Article |
| ProdID: | 70015706 |
| Citation Author: | Crowley, K. D.; Naeser, C. W.; Babel, C. A. |
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| Citation End Page: | 336 |
| Citation Issue: | 3-4 |
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| Citation Language: | English |
| Citation Larger Work Title: | Earth and Planetary Science Letters |
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| Citation Number Of Pages: | 8 |
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| Citation Search Results Text: | Tectonic significance of precambrian apatite fission-track ages from the midcontinent United States; 1986; Article; Journal; Earth and Planetary Science Letters; Crowley, K. D.; Naeser, C. W.; Babel, C. A. |
| Citation Start Page: | 329 |
| Citation Volume: | 79 |
| Citation Year: | 1986 |
| Type: | citation/reference |
| Text: | Tectonic significance of precambrian apatite fission-track ages from the midcontinent United States; 1986; Article; Journal; Earth and Planetary Science Letters; Crowley, K. D.; Naeser, C. W.; Babel, C. A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 1986 00:00 -0600 |
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