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<br />u <br /> <br />cross-sections. The north-south cross-section (M32) shows that the beds <br />are dipping steeply to the north. The I coal seam was used to correlate <br />the drill logs used to form this cross-section. This seam was selected be- <br />cause it is the shallowest coal seam with a developed structure map. <br />Map M34 presents a structure map of the base of the I coal seam. The <br />structure map shows the location of the Big Bottom Syncline. The dip of the <br />Upper Williams Fork units in the potential AVF areas is toward the north. <br />The G, H and I coal seams are shown on the two cross-sections. Massive <br />sandstones exist above and below the F coal seam (refer to Map M33) and <br />between the G and H coal seams. These sandstones have been labeled the <br />First, Second and Third White Sandstones in some reports. A thick section <br />of Lewis Shale is shown in the Big Bottom Syncline area on Map M32. <br />Geomorphology and Soils <br />Geomorphic mapping shows the limits of potential AVFs on Map M35A. The <br />break in slope between surrounding hillsides and essentially flat-lying <br />deposits, including some fan deposits, occurs in No Name, Johnson, Pyeatt <br />and Flume Gulches. A distinction between alluvial and colluvial deposits <br />cannot be made. However, terracing is not evident except in lower Johnson <br />Gulch, where the channel has incised in fill material, leaving the old flood <br />plain as a terrace. The drainages are probably a mixture of alluvial and <br />colluvial fill materials. Neither reworking of material nor the existence of <br />old meanders is evident. Because the drainages are ephemeral, material could <br />only be transported during periods of snowmelt or intense rainfall. <br />2-535 <br />