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bir. James Pendleton <br />August 30, 1983 <br />Page 2 <br />• <br />In these areas, the bending moment will be less and <br />the extent of lithification may also decrease. <br />Fourth, the top of the channel may be covered by any <br />"normal" depositional sequence. As the situation has <br />developed at the Mt. Gunnison #1 Mine, drill hole <br />control shows the rider coal that oersists in the area <br />of the portals. This serves as an indicator of a flat <br />depositional surface above the sandstone. This will <br />be discussed in conjunction with section A-A'. <br />Finally, crustal deformation occurs. The reorienta- <br />tion, which takes place has no effect on the occur- <br />rence of the fractures. They may occur on the down- <br />dip side of the valley or beneath stable slopes as <br />well as the updip side of a valley beneath a landside. <br />Simply stated, these fractures developed at such an <br />early stage that their location in relation to more <br />recent geology and geomorphology is of no significance. <br />The second attachment (See Figure 2) is a sandstone/ <br />shale roof lithology map. In addition, this map shows <br />structure contours and the location of cross sections <br />• A-A' and B-B'. It should be noted that the anomaly in <br />the top of coal structure contours is directly related <br />to the occurrence of the sandstone. This is strong <br />evidence of compactional deformation. <br />The third attachment (See Figure 3) is cross section <br />A-A'. This cross section is based on a surveyed pro- <br />file of the mine roof along entry number 4. The air <br />rotary holes were drilled immediately behind the <br />portals during construction. The additional holes on <br />the cross section were drilled for engineering and ex- <br />ploration purposes. This section shows areas and thick- <br />nesses of known occurrences in the drill holes as well <br />as the fractures which were encountered along entry 4. <br />Two points of significance should not pass unnoticed in <br />relation to section A-A'. First, there is a very signi- <br />ficant dip reversal on the surveyed profile. This is <br />assumed to be the result of compactional loading by <br />the sandstone. Second, there is a well developed rider <br />coal distributed throughout the area. One can assume <br />that the rider coal was deposited on a horizontal <br />surface. When the shales on the flanks of the sand- <br />stone are "decompacted" beneath the horizontal rider, <br />the Flexure of the coal seam is apparent (see hypo- <br />thetical development sequence). <br />u <br />- - ~-. .....- -~,r <br />