1. Geology and Eruptive History of the Late Oligocene Nathrop Volcanics, Central Colorado Volcanic Field
- Author
-
Emery, William Daniel
- Subjects
- Geology, Volcanology, Colorado, Central Colorado Volcanic Field, vitrophyre, welding, pyroclastic, pyroclastic fall, pyroclastic flow, Ruby Mountain, Sugarloaf Mountain, Nathrop
- Abstract
The Nathrop Volcanics consist of rhyolite lava and pyroclastic deposits located on the eastern shoulder of the upper Arkansas Graben in south-central Colorado and are part of the extensive late Eocene-Oligocene Central Colorado Volcanic Field. Deposits of the Nathrop Volcanics at Ruby Mountain consist of a lower lithic-rich lapilli tuff (ca. 3 m thick) with multiple layers that are reversely graded with respect to pumice clasts and are overlain by an approximately 30 m thick lithic-poor tuff breccia containing pumice blocks up to 1 m in diameter. The upper portion of the tuff breccia transitions up into a 5 m thick, moderately to densely welded tuff (vitrophyre), which in turn is overlain by a 20 m thick flow-banded rhyolite. A similar stratigraphic sequence is found at Sugarloaf Mountain (
- Published
- 2011