Upper Cretaceous (Campanian) coal resources of western Colorado
— D. Keith Murray

Colorado encompasses parts or all of eight distinct coal-bearing regions, which cover nearly 30 percent of the total area of the State (fig. 1). These eight regions, within which are located 21 designated coal fields, contain more than 10 percent of the total coal reserves of the United States above a depth of 1,830 m (6,000 ft), or at least 434 billion short (394 billion metric) tons of in-place coal. Of this resource, more than 273 billion short (248 billion metric) tons, or 63 percent of the total, have been estimated for the Green River, San Juan River, and Uinta coal regions of western Colorado (see Murray, 1980a, 1980b). Although most of this re source is believed to consist of coals of Cretaceous age, no data presently are available regarding the breakdown of coal resources in Colorado by geologic age or formation. However, based on the known distribution and thicknesses of the widespread, multiple (often numbering 20 to 30 or more) coal beds encountered in the Mesaverde Group and equivalents (essentially, Campanian in age), there is little doubt that the bulk of the coal resources of Colorado lies within this sequence. In the southeast part of the Uinta region, for example, total net thickness of Mesaverde coals in places exceeds 24 m, based on an evaluation of oil and gas well geophysical logs in the area (see Murray and others, 1977, p. 389). In the Danforth Hills coal field, Rio Blanco and Moffat Counties (fig. 1), total coal thicknesses in the 30-47 m range have been noted, based upon subsurface information. To date, western Colorado coal fields have produced more than 224 million short (203 million metric) tons of coal, which amounts to nearly 33.5 percent of the State's cumulative production, from 1864 through 1980, of nearly 670 million short (608 million metric) tons. During 1980, the three western Colorado coal regions produced more than 17 million short (15.4 million metric) tons of coal, or 90 percent of the State's total. Virtually all of the historic coal production from western Colorado has come from Cretaceous age sequences; and all of the present production consists of coals of this age. Based on preliminary data from the Colorado Division of Mines, nearly 12 million short (10.9 million metric) tons of coal was surface-mined in western Colorado during 1980, which comprises 70 percent of all coal mined in that region and nearly 93 percent of all surface mined coal in Colorado.