1988-04-11_PERMIT FILE - C1981008A (4)

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State Reg. in mesa tops and benches, and recent alluvial sand and gravels restricted to stream flood plains (Williams, 1964) . Thicknesses of these deposits are highly variable owing to the nature of deposition. The maximum known thickness of alluvial sands near the mine is 18 feet on the south side of Tuttle Draw. Gravel deposits of unknown thickness are found along the San Miguel River at Naturita, Colorado. Mancos Shale (Late Cretaceous) . The youngest formation found in the Nucla Syncline, with the exception of Quaternary deposits, is the Mancos Shale. It is a drab dark gray, homogeneous, soft, fissle, marine shale which attains a maximum thickness of ap- proximately 4,000 feet where fully present. Nbst of the Mancos has been removed by erosion in the Nucla Syncline except for the basal portion which forms a few isolated hills south of Nucla. Dakota (Naturita) Sandstone (Late Cretaceous) . The contact be- tween the Mancos Shale and the underlying Dakota Sandstone is conformable, and in sane cases, gradational (Lohman, 1965) . Basically, the Dakota consists of resistant yellowish to gray, fissile sandstone and conglomeratic sandstones interbedded with dark gray carbonaceous shales, impure coal, and a basal con- glomerate (see stratigraphic column, Figure 6-2 in Site Specific Geology Section) . Total maximum thickness for the Dakota in the area is estimated to be approximately 200 feet (Williams, 1964) . Well exposed sections are found in Coal Canyon to the northwest of the mine site and along the rim of the San Miguel River Valley to the southwest. It outcrops extensively along the axis of the Nucla Syncline. With the underlying Burro Canyon Formation, it forms resistant mesa tops and sharp canyon walls. Burro Canyon (Cedar Mountain) Formation (Early Cretaceous) . An erosional uniformity of regional extent marked by the basal con- 6--/