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<br />The Mesaverde Group is approximately 3,000 feet thick and conformably overlies <br />the Marcos Shale. It consists of the Iles Formation and Williams Fork <br />Formation. <br />Tne Ile; Formation is the lower unit and is approximate:'/ 1.500 ft. thick. It <br />consists of interbedded light-brown to write, massive, fine-era?red, <br />ie7ge-forming sandstones, brown to black cartlcnace~;us sna'e. sa~^dy shale and <br />teal beds. The coal bees are ar igned *.o the lower toes group of the <br />Mesaverde, and are distributed throughout the middle and upper Darts of the <br />formation. Four persistent sandstone bees occur 'Nithin the Iles Formation. <br />he'I dr?: 1) th2 Tow Cr?e!c 5dCC5tOne me'mW_r dt the odic: <br />?% a dcubte leeg?-formine 5ancs:one seeuence 300 feet or mcr'_ aoov2 the base; <br />_% a light_grdy idnds7Cn2 S2GUenC? Of /arldbl? CCmCC51t'On aiiOCldt2d 'Nlth the <br />upper '.iVO. 3) coals of the lower group S1L'Jdt?7 atlou*. 400 :c 1,000 feet above <br />:ne base: and 4) the Trout Cree< sancston? member .vhicn cans the formation. <br />Tne Trout Creek Santlstene is a 50 to 100 f00L thick, light-brown to <br />light-gray, fine-grained, massive sandstone. <br />The upper unit of the Mesaverde Group is the Williams ForK Formation which is <br />aptlrox`mately 1,000 to 2,000 feet thick and includes all beds betwe?n the top <br />cf the Trout Creek Sandstone Member and the bast of the overlying <br />_ Le'Nis Shale. The formation 15 conrormabla dt itS OaSe and :oo, and It 15 <br />divided into three units, the lc'.ve`, middl? arc uocer un`75. <br />-he lower unit is about 1,000 fee: this<, oonsist'ng ~f sequences of shale, <br />thin sandstone beds, sandy shale and several coal beds. The middle coal group <br />of this unit contains the coal seams of ?conomic imoertdnc? for melt of the <br />mining in this area. In ascending ord2r thou ar? the :1Cif C:'??.r, Wedge dnd <br />Lennox s?ems. 411 the mines considere; in this C:1iS surf ac? wat?r area mine <br />One Or mCr? Of tne52 CCdI; exC?pt Lhe ~.r3S;'J Gap Mlne and th? '4eadows N0. 1 <br />Mine. Tne Wedge is the only seam ?.<tract?d at the Se:^.eca ?i-:J n'ne. The <br />LeMOx 52am hd5 been e'COed tnr'pUgnJUt mU:h C Lh2 m...^.e Sit? and the Wolf <br />Creek seam lies toe de?p for reco`/?ry by surface mining me:heds. The middle <br />unit of the Williams Fork Formation includes a massive, 'Knit?, cross-bedded, <br />cliff-form'ng sandstone about 100 to 200 feet thick, called the Twentymiie <br />Sandstone Member. The upper units of the Williams Fork Formation consist of <br />interbedded sandstone, sandy shale, shale, sandstone and several thin coal <br />beds of the upper coal group. <br />Above the Mesaverde Group is the L?'.vi; Snaie, which is a 1.500 to 2,000 foot <br />thlck i2gUenC? := da r:<-yra~ to o~'Ji ;n, ~cmccancus marine i^ai? Nl to i2'rer37 <br />thin interbedded santlstcnes an;; •=a'care~us concr?.ions. <br />UnC:nsJllddt?d ai~,vidl deCO:':; Cf QUat?r.ndrv 3y'? CCn;t~tUt' t'''.9 youngest <br />ge^iCg'C 'Jniti in the 3r?a antl are jFn2`3iiy 'a;i than JQ r??: tnlC<. ne <br />ma'.<imUm thlCkne;S Jf the52 Ur,CCnSJ~iddt?7 d2COSi:; Occurs to Cne ramGd Ri`!er <br />alluvium 'Nhicn ii estimated to be less than lOC feet thic:< (3rogden and Giles, <br />1481). These de?osits are fount .Heir a:+.?nsiveiy a'ong the (amoa River, <br />Trout, Middle, `oidel, Fish. Sage a.^.~ Drv Creeks 3nc :~;nsi;r eredrminat9l! cf <br />clay, sand dnd i?ntlCUlaf, dtstontlnuous gra`/?i 13`/er';. <br />-25- <br />