Late Cretaceous uplift and volcanism on the north flank of the San Juan Mountains, Colorado
Dickinson, Robert G; Leopold, Estella B; Marvin, Richard F (1968) Late Cretaceous uplift and volcanism on the north flank of the San Juan Mountains, Colorado. Quarterly of the Colorado School of Mines, 1906-, vol.63, no.3, pp.125-148, 1968
| Authors | Dickinson, Robert G; Leopold, Estella B; Marvin, Richard F |
|---|---|
| Year | 1968 |
| Title | Late Cretaceous uplift and volcanism on the north flank of the San Juan Mountains, Colorado |
| Source | Quarterly of the Colorado School of Mines, 1906-, vol.63, no.3, pp.125-148, 1968 |
| ISSN | 0010-1753 |
| GeoRef | 1968-056976 |
| Keywords | absolute age; areal studies; Cimarron Ridge Formation; Colorado; Cretaceous; dates; Late Cretaceous lavas; Late Cretaceous uplift; Mesozoic; minerals; North America; Rocky Mountains; San Juan Mountains; San Juan Mts.; stratigraphy; structural geology; tectonics; U. S. Rocky Mountains; United States; uplifts; volcanism |
Abstract
Rhyodacitic flows, flow breccia, tuff breccia, and associated conglomerates, here named the Cimarron Ridge Formation, crop out in the Cimarron Ridge area on the north flank of the San Juan Mountains, Colorado. Epiclastic volcanic rocks in the formation contain pollen of Maestrichtian age, and K-Ar age determinations on mineral separates from lavas and related dikes indicate an age of about 66 m.y. The volcanic rocks were deposited unconformably on an erosion surface that truncates folded and faulted Upper Cretaceous Mancos Shale, Fruitland Formation, and Kirtland Shale. The deformation and erosion apparently occurred in Maestrichtian time inasmuch as pollen of that age has been identified from the upper part of the Kirtland Shale. The Telluride Conglomerate of early Eocene age unconformably overlies the volcanics.