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Structural orientation of surface outcrops in the Lease area is difficult to determine <br />because of the poor quality of most exposures. Measured dips rarely exceed 10 <br />degrees. Dip directions are generally towards the synclinal axis of the South <br />Rangely Syncline, a feature that transects the north eastern part of the Lease <br />boundary (Figure 4-9). <br />Faults are apparently not abundant on the Lease. The Dudley Bluffs Graben, which <br />is a major structural feature on the Piceance Creek Dome, approaches the Lease <br />from the southeast (Figure 4-9), but dies out after crossing Ryan Gulch. Smith and <br />Whitney (1979) indicated that a fracture system may extend along strike onto and <br />across the Lease towards Yellow Creek. Geophysical studies near Yellow Creek by <br />Campbell (1977) suggest that fracturing and/or faulting associated with the Dudley <br />Bluffs system may be present. Mapping by Anne Eckert (unpublished master's <br />thesis, University of Colorado) confirms the presence of fractures in Yellow Creek <br />near the confluence of Corral Gulch and Stake Springs Draw. Although it is <br />probable that fractures and minor faults associated with the Dudley Bluffs system <br />cross the southwestern corner of the Lease, it is not clear at the present time what <br />significance they may have. They probably will not affect commercial exploitation of <br />the Lease. However, additional detailed field mapping and study of aerial <br />photographs should be done to quantify the intensity of the structure. It is probable <br />that the fracture system does exert a dominant control over groundwater mobility, <br />both vertically and laterally. Drilling by the U.S. Bureau of Mines (CH 01; see Figure <br />4-11) near where the Dudley Bluffs Graben crosses Ryan Gulch is reported to have <br />generated very large volumes of groundwater, even though the hole was 1,300 feet <br />north of the graben. <br />Most ridge tops, flats and valley slopes on the Lease are covered by a thin veneer of <br />soil. Soils are rarely more than several feet thick, are low in humic material, are <br />generally well drained, and usually quite sandy. Soil mapping in the Lease area has <br />identified ten types (U.S. Bureau of Land Management, 1983, page 73). Dominant <br />soils include the Rentsac, Rentsac/Piceance, Piceance and Yamac Types. Below <br />the soils, weathered regolith may be present down to depths of 10 to 20 feet. <br />Daub & Associates, Inc. Page 4-35 NSI Mine Plan 2010 Rev. <br />Printed: 7/5/2010 Section 4 Geology