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<br />_17_ <br />The Cretaceous to Paleocene aged Raton Formation is exposed at the surface in <br />the study area. It rests unconformably above the Vermejo Formation and has a <br />total thickness of. 1,200 to 1,600 ft. The base of the Raton Formation <br />consists of a buff to gray pebble conglomerate a few inches to several feet in <br />thickness. Most of the Raton formation is composed of very fine to medium <br />grained sandstones including arkose, orthoquartzite and graywacke which are <br />interbedded with gray to dark gray siltstone and shale. The upper 100 to 200 <br />feet of the formation tends to contain coarse grained, arkosic sandstones and <br />light colored shales. <br />The coal seam which is being mined at the Golden Eagle Mine is the Maxwell <br />seam, and the New Elk Mine is located in the Allen seam. Both the Allen and <br />Maxwell seams are located in the middle of the Raton Formation of Cretaceous <br />age. The Allen seam lies stratigraphically beneath the Maxwell coal seam. <br />The seams are separated by a thin interburden strata which varies in thickness <br />from a few feet in the New Etk Mine to a few tens of feet in the Golden Eagle <br />Mine. <br />The Paleocene Poison Canyon formation unconformably overlies the Raton <br />Formation and has a thickness of approximately 600 feet in the study area. It <br />occurs as small isolated outcrops, probably no thicker than 200 feet near the <br />study area. This formation consists of massive, very coarse arkosic <br />sandstone, pebble conglomerates, and thick shales. <br />Sills and dikes associated with Tertiary volcanism intrude the Vermejo and <br />Raton Formations and are visible in the Picketwire Valley. They range in <br />thickness from a few inches to greater than 20 feet and are primarily composed <br />of basalt. <br />Quaternary deposits consist primarily of river terrace and floodplain deposits <br />associated with the Purgatoire River and its tributaries. The study area <br />contains two levels of rock benches that formerly may have been referred to in <br />the literature as Beshoar and Barilla pediments. The applicant's consultant <br />has interpreted these as strath terraces with an alluvial veneer. These <br />strath terraces are located approximately 90 to 170 feet above the river in <br />the study area. They have been eroded from shale and siltstone containing <br />thin interbeds of fine to very fine, silty sandstone. The overlying alluvium <br />has a maximum thickness of approximately 35 feet and is composed of <br />predominantly silt and sand containing pebbles and occasional boulders. <br />Two levels of alluvial terraces were identified adjacent to the Purgatoire <br />River. These terraces are located 5 to 10 feet and 40 to 50 feet above the <br />river in the study area and have been investigated by Powell, 1952. They are <br />composed of relatively unweathered, gray to light tan alluvium overlain by <br />medium to dark brown sandy overbank deposits. These terraces support typical <br />hydrophytic vegetation characteristic of floodplains and contain ground water <br />hydrologically connected to the river. Absolute dates on the alluvial <br />deposits are not available; however, in analogous areas of the Rocky Mountain <br />Region, the strath terraces are of Pleistocene age and the alluvial terraces <br />of Holocene age. <br />