2013-02-19_GENERAL DOCUMENTS - C1981014

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Southfield C1981014: MT6 4 February 19, 2013 Shale, the Trinidad Sandstone and the Vermejo Formation (these are illustrated in Figure 3 of the Permit Application Package, aka the PAP). The Pierre Shale outcrops approximately 1.5 east of the mine area. The shale unit consists of 3,900 feet of olive -gray clay and silt layers that contain bentonite and marine fossils. It is a non -coal- bearing unit that exhibits very low hydraulic conductivity and thus is considered to be a relatively impermeable unit. At the top of the Pierre is a sequence of thin, inter - bedded sandstones and mudstones. The Trinidad Sandstone, directly above the Pierre Shale, outcrops about 1.0 miles east of the mine site and is composed of massive buff to yellow sandstones ranging from 40 to 90 feet in thickness. The Trinidad Sandstone is indicative of a prodeltaic depositional environment. The Vermejo Formation overlies the Trinidad Sandstone and is the coal- bearing unit of mining interest to the Southfield operation. The Vermejo Formation consists of a complex network of mudstones, siltstones, sandstones and eleven coal seams, all indicative of a vast fluvial delta and plain sequence. The coals developed in the backwater swamp areas of the river delta. The coal seams of economic importance in the area are Monarch, Red Arrow, Jack O'Lantem, Vento, Manley and Rex Carbon. Total thickness for the Vermejo sequence is approximately 925 feet. The coal seams mined at the Southfield Mine are two of the six principal seams present in the Vermejo Formation — the Red Arrow and the Jack O'Lantern. The Red Arrow seam ranges in thickness from 4 to 7 feet and is a moderate to high sulfur coal with 3 recognizable units separated by bony layers of ash. The Jack O'Lantern seam is a low sulfur coal that ranges in thickness from 4 to 8 feet and also consists of 3 recognizable units separated by boney ash layers. The permittee has provided a complete coal, roof and floor analysis in the permit. For further information refer to Section 2.04.6 of the permit. Ascending upward on the stratigraphic column from the Vermejo Formation is the Raton Formation, a unit consisting of two members- a basal sandstone and muddy -sandy layer. The Raton averages 650 feet in thickness. The erosional base of this unit marks the top of the Vermejo Formation in the Southfield mine area. There are no coal- bearing units found in the Raton, since its character indicates that a period of increased uplift and subsequent erosion in the area followed that of the depositional low- energy environment found in the Vermejo. Uncomformably overlying the Raton Formation are the sediments of the Poison Canyon Formation. Similar in composition and character to the Raton, the Poison Canyon Formation is coal barren and is 200 feet in thickness of alternating beds of mudstone and sandstone. Covering most of the topographic ridges in the Southfield mine area are a series of Pleistocene boulder /colluvial /alluvial deposits. Most of the boulders consist of gneiss, schist and sandstones derived from erosion and mass wasting of the Wet Mountain uplift to the south and west. Depositional thicknesses range from 5 to 100 feet in places near the mine site, with 20 feet recorded in the loadout area of the mine.