| State | Texas |
|---|---|
| Name | Eagle Mountains caldera volcanic rocks |
| Geologic age | Oligocene |
| Lithologic constituents |
Major
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow, Pyroclastic-tuff)
Minor
Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic-tuff)
|
| Comments | Total of about 3,000-4,000 ft of eruptive rocks: lower rhyolite, a sequence of tuff, flow breccia, volcanic breccia, extrusive and intrusive rhyolite, with sedimentary rocks at base, thickness more than 1,000 ft. Trachyte porphyry--hard, compact, weathers to angular blocks, thickness as much as approximately 750 ft. Upper rhyolite--rhyolite including an upper volcanic breccia, flow breccia, and patches of basal conglo.; volc. breccia fragments of volc. rock, quartzite, and limestone in aphanitic matrix, white to lt. gray; rhyolite, aphanitic, comapct, brittle, intensely fractured, thickness 1,500 to 2,000 ft at Eagle Bluff. |
| References | Bureau of Economic Geology, 1979, Marfa Sheet, Geologic Atlas of Texas: Bureau of Economic Geology and The University of Texas at Austin, scale 1:250,000.Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000. |
| NGMDB product | |
| Counties | Culberson - Hudspeth - Jeff Davis |