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34 CONTRIDUT10N6 TO ECONOMIC GEOLOGY ~nring beds to t~,nruwie formation of Lnte Cretaceous age. Jillis (1912), ns n result of n short. visit. to the region, agreed to the parntioD of the cool-bearing rocks as advocated by Lee, bat referred e Vermejo to 1lfontnnn time and Use Raton formation to earliest Ter- nry or latest Cretaceous time. The Cretaceous-Tertiary boundary in the Trinidad coal field was ter determined by ]frown (1943) to be several hundred feet above le hose of the Raton fm•mntion; he assigned the upper port of the nton formation to the Paleocene. Later reports in this region by o Geological Survey Dave followed tl~e ngc ussigmnents of 13rown. As pert of the present investigation, areal reports on the geology pd coal resources of parts of the Trinidad coral field linve been pub- slled by Wood, Johnson, Enrgle, and others, 1951; Johnson and Ste- hens,1954a,1954h; Wood, Johnson, and Dixon,105G,1957;Johnson, 958a, 1958b; n~td IInrbour and Dixon, 1959. The con] deposits of Ie Raton basin were briefly reviewed by Carter in 195G, and in that ear Johnson and ~Vood (1956) described the uppermost Cretaceous nd Tertiary st.rat.igrnplly of the basin. GEOGRAPHY LAND FEATIIAES The'frinidnd coal field (pl. 12) is in large port a highly dissected Aland area in the westernmost part of the Great Plains province; is western margin lies along the ensteru foothills of the Sangre de ;risto 111ountnius. The cool field is mode up of rocks that are limited o the deepest part or trough of the 12nton structural basin (Johnson nd Wood, 1956, p. 707) of Colorado and New ltfexico. Along tl~e •estern and eastern boundaries of the field the more resistant beds f the'1'rinidnd sandstone separate the coal field from the surrounding olvhnud areas that are underlain by the Pierre shale. The southern margin of the Trinidad coral field along the Colorndo- 1ew lllexico State lice is marked by a high, relatively flat, and intri- ntely dissected divide between the Pw•gntoire and Canadian Rivers. n the northern port of the field, north of the Cuchnrn River, the hills re low and rolling, and they diminish in height to the north ~ebere he Raton 11[esu region merges into Huerfnno Pnrk. Surface altihules range from G,150 feet near Triuidnd and 6,230 set near ~i'alsenhm•g, along the eastern edge of the coal field, to ]liludes of 12,708 feet on Enst Spanish Penlc and 13,628 feet on }Vest Spanish I'enk. These two conical mountains rise nbrup[.ly above he surrounding counh•y, and are the domiunnt lmnhnnrks of the egim~. 1'he Inud surface slopes from the Spanish Peaks to the north, ast, and south in n series of discontinuous steplike platforms. The RE60URCE8 OF TRINIDAD COAL FIELD, COLORADO 735 igneous nmsses that comprise Dike ]llountnin and the Alnc~ills in the northwestern extremity of the coal field are also prominent topo- graphic features. Igneous dikes crisscross the cool field, nod because of their resistance to erosion they strand ns relatively straight vertical walls as much ns 100 feet above the surrrounding country. DRAINAGE Tire Trinidad coal field is drained by streams tributary to the Arknnsns River, The Huerfnno, Cuchnrn, Apishnpn, end Purgn- toire Rivers are the main streams that drain the area (pl. 12) ;they flow generally eastward from the mountains to the plains. The headwaters of the Huerfnno River are near the crest. of the ~ Sangre de Cristo Dlowltains. The Huerfnno River flows across Huerfnno Pnrk and south of the southernmost extension of the Wet Dfountnins, where it passes within 2 miles of the northern end of the Trinidad coal field and then flows northeastward across the plains to the Arknnsns River. ~Vithiu the coal field a low rolling divide separates the drninnge system of the I-Iuerfnno River from tlmt of the Cuchara River to the south. North and west of the Spanish Yanks the 1~•inidnd coal field is I drained chiefly by the Cucbnra River and its tributaries. The Cuchnrn River bends Went the crest of the Sangre de Cristo }}fountains west. of }Vest Spanish Perak, skirts the coal field for n short distance, and then crosses the field f.hrough n wide valley in a northeastward direction. It crosses the plains t.o Row into the Huerfnno River a ~ few miles above its caljunctiou with the Arknnsns lliver. A high rugged divide culmiunted by the Spanish Peaks and marking the Iiuerfmlo-Las Animas County line sepnrntes the drninnge system of the Cuchnrn River from the drninnge systems of the Apishnpn and Purgntoire Rivers to the south. i The Apishnpn River starts on the southwest slope of }Vest Spanish Peak in the western port of the Triuidnd cool field, and flows across the field in n general enshcard direction. On the plains it flows in n northenshvnrd direction to its confluence Frith the Arknnsns, River. .\n intricately dissected divide in the coal field, locally known ns "Pine Ridgo", sepnrntes the drninnge bnsiu of the Apishnpn, River from the drninnge Wren of the Purgntoire River to the south. To the west the two drninnge systems are parted by n high rolling divide, which, lienr the Haerfnuo-Las Animus County line, separates the three basins drained by the Cuchnrn, :lpishnpn, and Huerfnno Rivers. 1'he southern part of the Triuidnd coal field is drained by the Purgntoire River and its h•ibutaries. The Purgntoire River is the largest perennial stream in the cool field. Three main branches, i