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of the upper Trinidad. These sands are generally fine to medium grained <br />and light gray to buff in color. Total Trinidad thickness ranges from 40 <br />to 90 feet. <br />Vermeio Formation. Overlying the delta deposits of the Trinidad are the <br />complexly interbedded mudstones, siltstones, sandstones, and coals of the <br />Vermeio Formation. These sediments were part of a vast fluvial delta <br />plain sequence prograding eastward on the "Trinidad Delta". Differential <br />compaction of the accumulating sediments and regional subsidence <br />concurrent with deposition allowed moderate thicknesses of coal to develop <br />in back river swamps of the delta plain. <br />The Vermeio Formation is the coal bearing unit of interest in the <br />Southfield mine area. In ascending order, coal horizons of significance <br />.include the Monarch, Red Arrow, Jack O'Lantern, Vento, Manley, and Rex <br />Carbon. Several.of these coal horizons contain more than one seam and <br />have been described in the past under more than one name. In addition to <br />these six principal horizons, the Vermejo includes several other <br />recognized coal units within the General Area. Stratigraphic <br />relationships of the six main horizons and other minor coal occurrences <br />are illustrated by Figure 3, General Stratigraphic Sequence. Total <br />thickness of the Vermeio sequence is approximately 925 feet. <br />The Southfield Mine is currently developing reserves in the Red Arrow and <br />the overlying Jack O'Lantern coal seams. Both seams are part of the <br />"Radiant Coal Zone" recognized by the Colorado Geological Survey. The <br />Red Arrow Seam is a moderate to high sulfur coal ranging in thickness from <br />4 to 7 feet, consisting of 3 recognizable. coal units. Atypical face <br />description is as follows: <br />Upper Unit 1.0' <br />Upper Parting 0.2' <br />Middle Unit 2.2' <br />Lower .Parting 0.5' <br />Lower Unit 2.0' <br />coal <br />bone / carbonaceous shale <br />coal <br />bone <br />coal <br />