OCR Text |
Show 41 the Dolores Plateau to the south and numerous mesas on divides between the larger streams. A copy of Coffin's map* is included with the maps (PV-225, 1-12) submitted in a separate roll and shows the principal topographic and geographic features with cross-sections of the underlying formations and structures, The canyon of the Dolores River extends northerly across the area, dividing It roughly into two equal parts, 'The canyon of the San Miguel River, a tributary of the Dolores River, extends northwesterly across the northerly part of the area. Both rivers are fed by a substantial and permanent supply of water from the San Juan Mountains to the southeast. They are the only permanent streams in the area, except for a few small streams from the La Sal Mountains to the west and from the Uncompahgre Plateau to the north. Most of the tributary canyons are dry most of the year. Virtually every canyon, both large and small, is flanked with one or more successive cliffs of sandstone that terminate above in benches or less precipitous slopes developed on soft, easily eroded shale. The wide, open areas of Paradox Valley, Sinbad Valley, Gypsum Valley and Disappointment Valley are open 4Coffin, R. C , Radium, uranium and vanadium deposits of Southwestern Colorado: Colorado Geol. Survey Bull. 16, pi. 1, Reconnaissance geologic map of the main carnotite area of southwestern Colorado, 1920. |