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. . . . 0652 The Cretaceous and Tertiary formations conlprise the foothills, which have steep slopes and narrow valleys. More detailed geologic data are given in appendix F. 18. Charmel characteristics. - In the headwater reaches upstream from Weston, Colorado, river mile 180, gradients are several hundred feet per nQle. Below that point to the vicinity of Long Canyon, river mile 164, slopes are in excess of 50 feet per mile. From Long Canyon to the mouth of San Francisco Creek, river mile 122, the stream bed decreases in eleva- tion at rates of between 50 and 20 feet per mile, and the channel capac- ity is about 15,000 cubic feet per second. River slopes, channel capac- ities, and other pertinent data are given in table 1. A profile of the river is shown on plate 2, appendix A. TABLE 1 PURGATOIRE RH'ER RIVER SLOPES AND MININUH CHANNEL CAPACITIES Inter- Approximate Miles vening L01'i-water Low-water Approximate Locality above !fJiles Elevation Slope Channel Houth by Feet above Feet Capacity River MSL per Mile c.f.s. Junction, North & 186 7,400 JII',iddle Forks 22 55.7 Not estimated ~louth of Long 16h 6,175 Canyon 7 26.3 15,000 Trinidad 157 5,987 35 19.2 15,000 Mouth of San 122 5,320 Francisco Creek 19. Soils. - The four soils groups found in the Purgatoire River drainage area vary greatly in character. In the upper or "estern part of the area above Stonewall, the Rough Stony and Alpine Meadow groups are mostly a complex of barren, rough, stony land. In the meadows the soils are usually shallow alld stony. IiLthosols cover mast of the area from Stonewall downstream to the front range belo" Trinidad. The dominant 7 , ~.i-