_GENERAL DOCUMENTS - C1981017 (262)

Home Browse Search

The Morrison Formation is of da Formation. This formation c itly colored, variegated shales, e units Q within this formation are h Ll V 1 The Cretaceous Age, Dakota nation, 0Y�e� ' This unit consists of 100 1 ored sandstone, which is locall is very resistant to erosion and i Sedimentary rock strata e; e mines are the Cretaceous Age Mancos and t Tertiary Age 'Wasatch Fors he 3to 4,U00 feet of dark gray a Mancos,000 he 000 shale consists of two sn, ember. This formation is highly erosive, wns, _ of broad valleys along the strike of this formation anu n„ in total suspended solids in areas east of the mines. The saline nature of this marine shale formation results in an increase in total dissolved solids downstream and east of the mines. Conformably overlying the Mancos shale is the Mesaverde Group. This group is divided into two formations; the Iles Formation and the 'William Fork Formation. The Iles consists of the basal Cozzette sandstone member; the middle member consisting of shales, siltstones and fine-grained sandstones; and the upper Rollins sandstones consist of ,nedium to very fine-grained resistant sandstones. The two sandstones are ridge and cliff formers_. The Williams Fork Formation consists of over 5,000 feet of sandstones, siltstones, shales and coals. This formation conformably overlies the Iles Formation and consists of marine and terrestrial deltaic deposits. The Williams Fork Formation is divided into three members; the lower coal-bearing Bowie member, the upper coal-bearing Paonia member, and the non-coal -bearing Barren member. The Bowie member is between 675 and 850 feet thick in the area of the mines, and is composed of four general submembers. In ascending order, these submembers are: 1 ) 420 to 480 foot thick coal-bearing lower Bowie shale; 2) 30 to 130 foot thick Middle sandstone; 3) 150 to 2U0 foot thick Upper Bowie shale submemoer; and 4) 50 to 100 foot thick Upper sandstone suorr,ernber. The lower oowie coal -bearing shale suomember contains several coal seams. These coal seams vary in thickness and lateral extent along the Grand Hoyback. In the area around the Sunlight Mine, there are thr-e minable coal seams; the "A-6" seam the 0 seam and the "U" seam. -he "A-d" seam acid the "C" seams have been previously mined, and the "C" and "U" seams are currently being mined in the Sunlight '' line. Three commercially minaole coals 0f the_ Lower Bowie shale suome'noer ( "A", "3", and L seams, are located in the area of the Aorth Thompson Creek ,lines. The north Thompson Creek 'lo. 1 ;dine is currently mining the seam. The i nact i ve 'd0. Z %line was wi th i n the "B" seam. i.n she area Jf the Coal Basin Mines, there are 140 fninaole seams. the "A" and "I seams. The "3" seam is oeiP,d mined at the Coal 3asin :lo. 1 , 3 ,�, and lines. The two seams are separated by U ro 39 `ee* of interourden.