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Lorencita Canvan Mine - Geo(aev rechnical Reoart <br />• interburden, the units located between the Ciruela coal and the Primero coal; <br />• Primero coal; and <br />• underburden, the unit that underlies the Primero coal. <br />Alluvium/Colluvium <br />The alluvium/colluvium material is a thin unit within the permit area and is confined to valley <br />areas of ephemeral streams. The alluvial/colluvial material is composed of clay, silt, sand and <br />gravel. Boreholes drilled into the alluvial/colluvial material indicated thicknesses ranging from <br />10 to 22 feet. <br />Overburden <br />The overburden is comprised of interbedded sandstone, shales and minor coal seams. The <br />sandstone beds encountered in the overburden aze massive, fine grained, well sorted with rounded <br />to spherical sand grains. The sandstone is crossbedded and thinly laminated with mud. These <br />features are indicative of a Fluvial depositional environment. The thickness of the sandstone beds <br />generally are less than 10 feet. <br />• Shale beds occurring in the overburden consist of grey to dazk grey hard shales and carboniferous <br />shales with interbedded coal laminae. Shale comprises approximately 90 percent of the <br />overburden with the sandstone less than 10 percent. <br />Two coal beds, the S and T seams, occur in the overburden in addition to smaller seams and <br />laminae. These two seams occur in the upper Raton Formation and, where not pinched out, range <br />in thickness from inches to two and one-half feet thick. <br />Data derived during the 1996 investigation at the site and previous studies indicate overburden <br />thicknesses ranging from 0 feet at the coal outcrop to 500 feet at higher vistas. The overburden <br />is greater than 100 feet in the aeeas of proposed subsurface mining activities. A map depicting the <br />overburden thickness is included as Map G-1. <br />Ciruela Coal <br />The Ciruela coal (R Seam) is the uppermost minable seam in the permit area and is of minable <br />thickness over 2,109 acres (Boyd, 1974). The Ciruela coal is located across the entire property <br />where erosion along ephemeral streams has not occurred. The seam pinches out along the far <br />eastern portion of the site. The thickness of the seam ranges from nearly six feet in the <br />southwestern portion of the rtntt ra ea to 1 2 feet in the eastern-do~ndip direction prior to <br />pinching out. The Ciruela c \ I bed thickness 's include on Map G . <br />tie , <br />Gcology-t75/December 16, 1996 g <br />