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<br />,,\:-,,'11.'\"/-'0:< .. . <br /> <br />- 16 ~ <br /> <br />The generalized terrain of this area is that of a very steep allu- <br /> <br />vial fan with its apex near the foot of Gallo Bluff. In detail, the <br /> <br />surface looks rather chaotic with numerous ridges, old channels, and <br /> <br />poorly drained areas. The material exposed at the surface and on the <br /> <br /> <br />sides of the old channels is predominantly a jumbled and ill-sorted <br /> <br /> <br />mixture of materials including ~hale and sandstone fragments of all <br /> <br /> <br />sizes, with a matrix of clay fObned from weathered Mancos Shale. The <br /> <br />.irregular topographic surface i~ an expression of the multiplicity of <br /> <br />channels, bars, and lobes forme~ by many earlier flows of viscous mud <br /> <br />that make up the major fan feature. Plate 3 is a tracing of a detailed <br /> <br />topographic map of the area whith is quite instructive concerning the <br /> <br />location and topographic expresqion of distributary channels, slope of <br /> <br />the mu~flow surface, and other tritical aspects of the fan area. <br /> <br />Some of the larger and mor~ extensive channels repr~sent former <br /> <br />through-flowing channels of Slate Creek as it shifted from one temporary <br /> <br />position to another in building the mudflow fan. One major former chan- <br /> <br />nel in particular (2d, plate 1) has in the very recent past crossed the <br /> <br />older fan and discharged mudflows into the Marble townsite from the <br /> <br />northwest. According to local reports, this channel was artificially <br /> <br />plugged and diverted to its present course by Marble residents to prevent <br /> <br />Slate Creek mudflows from entering the town. From our field and photo <br /> <br />inspections, it appears that the diversion is indeed man-made, which <br /> <br />serves to show how temporary and easily diverted the channel location <br /> <br />is at any given time. In our opinion, the re-entry of Slate Creek into <br /> <br />this former channel is only one large landslide or mudflow away - pro- <br /> <br />vided the landslide is of the required size and location, or the flood <br /> <br />of the necessary volume, viSCOSity, and erosive energy. The detailed <br /> <br />. '~r"' .' <br />