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J~. CONTRIdU7•ION6 TO ECONOMIC GEOLOGY )iron, 105G). '1'I~rstern limb of the synclino has n gentle clip, vherens the e•estcru limb dips steeply unrl is verlicnl to ovm•htrned in laces. The Greenhorn nut.icline plunges smdhwarrl from the Wet. lonnlnins, and splits the La Vets syncline into n major syncline o the west, and n minor one, the Dclcarhon syncline (,iohnson and etephens, 1054n), to the east. Iu cross section the Delau$on syncline s shat lower ^nd more syntmet tic than 1 he La Vets syncline. THRII6T FAULT6 Une to three thrust faults parallel the east front of fhe Sangre de `risto Iltouuhtins along the steep western mm•gin of the coal field. two f;nrlt blocks northwest of ]at Vehr are crnnposed of two or possil)ly tree imbricate thrust plates east of Ibe S:wgre de Cristo thrust fault. )ne plate, with e•bich the coal-bearing Vermejo fm•mntion is nssoci- ted, is complicated by an overturned and compressed syncline and nticline whose axial planes parallel t.hc trace of the major thrust wlts nud are inclined to the west. The anticline Les been sta•ongly tented by a tbrnst fault. At the southm•u terrninns of n thrust fault. south of Cucharn fuss ear the west. margin of t.be cool field two lent faults trend soutbeast- ~nrd, and cut the roal-bearing format ions. NORMAL FAIILTS Normal faulting is not. cbnr:rcteristic of the coal field, but isolated ;roues of normml faults uccrn• througbout the nreu. Two nm•mnl rolls at the north end of the coal field cut fhe t.lvo flanks of the De.lcurbmt synrliuc, and Freud generally parallel to the axis of Ibe yncline with fhe upthrown sides toward the axis of the syncline. fhe throw of enc6 fault is less than 50 feet. 'The bighly frnclurerl unrl altered block of serlintentary rooks that. es bet d'cen Uto Spuuisb Peaks seems to have been brought from rleptb y the intrusion of Ibe 1$ast Spanish Penk magnur. 'fhe relations f fhe faulting ore obscured by curer, bal. the faults seem to be ormal. The rucks arc bighly fractured nud fnnlterl, and only the utjm• faults wme umppcd. 'l'be verlicnl displacement along these mjur faults may br as umch as a,nnn feet. Several small normal fnuhs rnrur nm•theast of \Veshnt. These uths Irend north, CIISI, Ilurtllca5t, nud northwest, and seem to be elated Io n snmll anticline m• dome. Faults north of the dome Irnve ecn dowuthruwn nn Ibe southern, sonlhensteru, ;uul srndlrwestern des; whereas faults south of the dome Lace been dotvuthrown on re western, northcvcstern, and northcaster•tt sides. i\fost of the RESOURCES OF TItINIDAD COAL FIELD, COLORADO 1~,`f • faults nro nearly vertical nud have displacements of less thi~l feet. Solitary vertical or nearly vertical normal faults occur locally, and nro of such small displacement nud extent that they are not. shown on the geologicmnp (pl. 12). FOLDS Tho Grcenhoru anticline, which splits the Ln Vetn syncline, plunges southward info the Triudad coal field. The intrusion of the Black hills magma on Lhe nose of fhe anticline bas further domed the in- truded sedimentary rocks, and beds of the Poison Canyon fm•ntntion arch over the southern part of the intrusive muss. They hove been eroded from the IIlack Ilillse]sewhere. The intrusion of the East. Spanish Penk stock has domed beds of the Coeburn fa•nrntion directly west mtd south of the stock, but beds to tho north and east of it. have not. been folded by the invasion of the mngntn. A narrow, slightly sinuous manoclinnl flexure is located 3 miles northwest of Aguilar. The monocline trends northenstwnrd througb beds of the Trinidad sandstone and the Vermejo, Raton, and Poison Cnuyou formations.' 'Tho rocks on the nortbenst side of the monocline are doe•nfolded through n zone less than one-fourth of a mile wide. Dips may he ns much ns 50° rat places. The verlicnl displacement is about. 50 feet nt. the eastern edge of the coal field, and it. increases sonthwest.wnrd to n maximum of dearly 200 feet.. The fold is sharp, and nt. places along the edges of the flexure the rocks increase in clip from less than 2° to more thmt 40° within horizontal distances of less then 400 feet (IIarhour and Dixon, 105:1, p. 464). AL Aforley n large mnfic sill, whicb does not. crop out in the map urea, has been iut.ruded bet.weml the Purgatoire fot•mn[imt and the Dnkoht snndstrnte of Early Cretaceous age, and has arched the beds above it. into nn irregnlnr dome called the Dforley dome. Raton Creek, whicb flows across the western Ilnnk of the dome, bas breached the anticline to expose beds of the Poison Canyod, Raton, and Vermejo fm•mntions, the Trinidad sandstone, and older Cretaceous rocks. Lt I he soot hweslern part. of the coal field are the Tercio anticline and the Cnnh•u syncline. Rincon Creek and the South Fm•k of the Purga- toira liiver have breached the anticline to expose beds of the Poison Canyod, llnlmr, rout Vermejo for•mafions, tbo Trindad sandstone; nnrl older Cretaceous rooks. Tho anticline may brave n closure of almost l,nnn fret. Several long, narrow, irregulnl• folds of low structural relief are prevalent. south of the Spanish Peaks. The axes of these folds hove no preferred orientation (R'ood, Johnson, nud Dixon, 1:157, pl. 2).