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Uplift on the west-southwest; and Grand Mesa-Piceance Basin on the north (Collins, 1976). Toooaraohv The topography consists mainly of north-trending hills and ridges separated by similarly trending drainage. Minor east-west trending draws and ravines are cut by tributaries to the major drainage. The portion of the area east of Stevens Gulch is very steep and rugged, with elevations ranging from about 6,400 to nearly 8,000 feet. In the portion west of Stevens Gulch the elevations range from about 6,800 to 9,600 feet, but the overall topography is somewhat less rugged. Slopes are covered with scrub oak and juniper at the lower elevations, and with aspen, fir, and spruce at higher elevations. Bedrock outcrop is poor even in the high-relief eastern portion, and is minimal in the north, west, and northwest portions of the study area (Map 2-7). Stratigraohv Regional Stratigraphy Generally, Paleozoic strata comprise the Elk Mountains on the East; Mesozoic and Cenozoic strata are exposed within the Uncompahgre Uplift, pre-Cambrian within the Gunnison Uplift, and Mesozoic • strata comprise the immediate North Fork Valley. The area is further modified by Tertiary intrusive porphyritic rocks, which are predominantly laccolithic in structure (west Elk Mountains, Hail, 1972), and Miocene basalt flows capping Grand Mesa (lunge, 1978). Local exposed lithologies range in age from Upper Cretaceous Mancos and Mesaverde to Holocene alluvial fill along the North Fork of the Gunnison River (Figure 2.00). The Mesaverde Group of Holmes (1877), has been extended throughout western Colorado, eastern Utah, and southwestern Wyoming, and represents a dominantly regressive sequence which formed in response to larger detrital input from the Cordilleran region to the west rather than contemporaneous basin subsidence (Weimer, 1976). The Rollins Sandstone Member (Lee, 1912) of the Mesaverde Group represents the basal regression of the Cretaceous Seaway, although Collins (1976) identified seven cycles of marine-nonmarine deposition in the Eastern Piceance Basin (Figure 2.01). The coal deposits of the area were deposited as the complex relationships of deltaic, fluvial, and barrier island facies were intermittently modified by transgressive-regressive cycles of the retreating Cretaceous shoreline (Figure 2.O1B). The coal bearing member of the Mesaverde Formation varies regionally in thickness from 500 to 1,000 feet and locally contains four to six minable coal seams in the North Fork Valley (Figure 2.00). The seams are in ascending alphabetical order, within the • stratigraphic interval 500 to 600 feet above the Rollins Sandstone - 7 -