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• The top of the Bowie Shale Member , and the <br /> uppermost of the three prominent marine sandstones in the <br /> district , the Upper Sandstone is up to 100 ' thick. It is <br /> virtually identical to the Rollins and Middle Sandstone <br /> units , except in having somewhat coarser , medium grain . <br /> The Upper Sandstone represents the final regression of the <br /> Cretaceous sea from this part of Colorado . Sedimentary <br /> structures indicate a predominantly southeasterly flow <br /> direction. <br /> The Paonia Shale Member , which includes the <br /> Placita-Sunshine coal interval , consists of lower and upper <br /> deltaic plain coal beds , shales , siltstones , and sandstones <br /> of fresh and brackish water origin. It is in general more <br /> -..• coarse grained than the Bowie Shale , and slightly more <br /> resistant to erosion. The base of the Paonia member over- <br /> lies the Upper Sandstone and is a coaly siltstone , approximately <br /> 2 ' thick. <br /> Above the siltstone is a 3 ' -7 ' coal bed , the <br /> Placita seam. The Placita is thickest in the southeastern <br /> part of the basin, and thins rapidly from Dutch Creek to the <br /> west and north. <br /> Approximately 50 ' -60 ' above the Placita <br /> occurs another coal seam, probably the Sunshine seam. The <br /> seam is 18"-4 ' thick in the Coal Basin area . <br /> The upper boundary of th-e Paonia is indistinct , <br /> • <br /> 25 <br /> M <br />