West Elk volcanic field, Gunnison and Delta counties, Colorado
— D. L. Gaskill, F. E. Mutschler, and B. L. Bartleson

The West Elk volcanic field covers about 1,600 km² in the southern part of the West Elk Mountains (fig. 1) and ranges in elevatior from about 2,100 m along the Gunnison River to 3,960 m at Wes Elk Peak. Tertiary volcanic deposits form a deeply dissected, south sloping volcanic plateau whose western and northern edge is imposing, almost continuous escarpment that culminates in the higher peaks of the Baldy Mountains. Most of the volcanic rock: were erupted locally from Oligocene intermediate-compositior volcanoes, which are related in time to the larger San Juan vol canic field south of the Gunnison River (Steven and Epis, 1968; Lip man and others, 1978).

 

The volcanic rocks have been eroded from the northern Dart o the map area (fig. 2), exposing a thick section of Mesozoic and Tertiary strata intruded by many Tertiary plutons. Reports and maps of the Hayden Survey (Peale, 1876; Hayden, 1881) remain excel-lent first references to this region. A geologic folio (Emmons and others, 1894) covers part of the volcanic field. The southern mar-gin of the field has been recently mapped in detail by Hedlund and Olson (1973, 1974), Hedlund (1974), and Hansen (1971). A wilderness study by Gaskil I and others (1977) covers the northern part of the area. Perhaps the best general discussion of the geology is in Hansen (1965).

 

Most of the volcanic field lies within Gunnison National Forest. Oak brush and scattered stands of pine and fir predominate to elevations of about 2,600 m. Spruce, fir, and aspen are the dominant forest communities at higher elevations. About 6 percent of the area is above timberline. Erosion has removed all but scattered remnants of the West Elk volcanic field east of the map area, has exposed many of the intrusive structures, and has cut canyons many hundreds of meters deep into the volcanic pile. Glaciation has sculptured the higher peaks and valleys.