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1 <br /> <br />2.09.6(2)(a) <br />The Rollins Alember is a conspicuous white to buff, cliff <br />forming sandstone and ranges in thickness from 150 feet to <br />over 200 feet. Although this sandstone forms a good <br />' regional subsurface marker, it is a poor local marker <br />because of lateral facies changes into shale. The I:ower <br />t Coal Member is composed of 50 to 180 feet of interbedded <br />sandstone, shale, and coal overlain by an irregular sandstone <br />t bed 50 to 100 feet thick. The unit contains three coal beds <br />of interest - A, B, and C seams. The Upper Coal Member <br />consisits of interbedded sandstone, shale, and coal similar <br />' to the lower member except t!~e beds are more lenticular. <br />This member ranges from 250 to 350 feet in thickness and is <br />' capped by a thick sandstone. The D, E, and F seams are found <br />in this sequence. Above the member, there is a thick sandstone and <br />shale sequence which does not contain coal. The general <br />regional dip is 3.5 degrees to the north-northeast but local <br />' dips of up to 6.25 degrees are found in the C seam. <br />The Cretaceous system of Colorado represents a rapid phase of <br />' extensive deposition of clastic sediments. These sediments <br />are both marine and non-marine in origin, resulting from a <br />' series of transgressions and regressions of the Cretaceous <br />interior seaway across a low lying coastal plain. In the <br />' North Pork area the coal-bearing sediments were deposited <br />during Campanian time leaving a predominantly regressive <br />sequence of strata. The source for the bulk of the sediments <br />was to the west during most of the C'pper Cretaceous, where <br />' orogenic activity was taY.ing place. <br /> <br />' 34 <br />