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CONTRIBUTIONS TO ECONOMIC 6EOLOOY
<br />ns di$er with ]rsty, and upland meadows have an nhtmdance of
<br />ass. Irrigation farming is practiced along the valleys of the major
<br />•sams, and alfalfa and some of tho larger grains are the principal
<br />cps. Dry farming is practiced on upland terraces and open fields
<br />interrnediats elevations, and timothy, millet, rye, and beans are
<br />oduced. Apples and plums nre grown in valleys where there is
<br />fficient water. Lumbering ]ras been carried on for many years
<br />thin the coal field, and sawmills still furnish timber to ranchers
<br />td the mining industry. The most important product of the region
<br />coal, which Itas been used for caking and domestic purposrs for•
<br />ore than 80 years.
<br />6ETTLEbIENT
<br />The three largest communities in the Trinidad oonl field nre along
<br />ho eastern margin where the three major streams flow from the up-
<br />end areas of the coral field onto the plains (pl. 12). Trinidad, with n
<br />opulation of about 12,200 in 1350, is on the Purgntoiro River; Wal-
<br />enburg, with about 5,000 people in 1950, is on the Cuchara River:
<br />nd A1,nlilar, with about 1,000 people in 1950, is on the Apishapn
<br />3iver. The rural population is centered mainly in small ranching
<br />tad farming communities along the Purgntoire, Cuchara, and Api-
<br />shapn Rivers.
<br />The population of the coal field ltas decreased steadily since 1930
<br />Sue in largo part to the decline in coal mining. Afnny of the mining
<br />;amps are now abandoned. The population of Las Animas County
<br />diminished from 32,368 in 1940 to 23,902 in 1950, and the population
<br />of Huerfano County decreased from 18,088 in 1940 to 10,549 in 1950.
<br />The population of the towns and cities declined nlrnost without ex-
<br />ception during this period, and it is suspected that the number of
<br />people on ranches rand farms also dwindled,
<br />TRANSPORTATION AND ACCESSIBILITY
<br />, The Trinidad coal field is easily reached by major railroads and
<br />i»ghwnys and by nn airline; many secondary roads rand several fi•eigbt
<br />rail lines extend into the coal field from population cantata. The
<br />main line of the Atchison, Topeka, rand Snntn Fe Railway passes
<br />through Trinidad and crosses the southeastern corner of the coal field.
<br />The Colorado and Southerl Rnilwny passes through Wnlseuhurg and
<br />Trinidad. A branch line. of the Denver nntl Rio Grande Western
<br />Railronrl serves \Vnlsenburg rand Ln Vetn. A short branch line frron
<br />Walsenburg skirts the northern end of the cool field. The Southern
<br />Division of the Colorado and Wyoming Rnilwny extends from its
<br />junction with the Atchison, Topeka, rand Santa Fe Raihvny up the
<br />RESOURCES OF TRINIUnu ,,gnu ..
<br />. Purgatoire River to tho Allen mine nenr Stonewall. T~dnd is
<br />served by Continental Airlines.
<br />BEDIAfENTARY ROCKS
<br />Sediutentary rocks of Paleozoic, l+fesozoic, and Cenozoic nge crop
<br />out in or nenr the Trinidad coal field. Rocks of pre-Cretaceous nge
<br />are exposed in the Sangre de Cristo )yfountains rand the \1'et Moun-
<br />tains west rand north, respectively, of the coal field, and crop out in
<br />the canyons of L-le I3trerfano, Cuclrnrn, Apishapn, rand Purgatoire
<br />Rivera northeast and east of the field. Cretaceous rand younger rocks
<br />crop out in and adjacent to the coal field.
<br />Exposures of sedimentary rocks of Lnte Cretaceous rand Tertiary
<br />age nre generally fair throughout the coal field. The rocks in areas
<br />adjacent to the Cuchnrn and Huerfnno Rivers are not so well exposed
<br />as in those areas adjacent to the Apishapn rand Purgatoire Ricers to
<br />the south, but nre better exposed than those on the timbered monnL•rin
<br />flanks at altitudes between 9,000 rand 11,500 feet. Exposures of rocks
<br />above the timberline are excellent. The sedimentary rroc:k sequence
<br />is sumtnnrized grnpllically on plate 12, and the areal distribution of
<br />tho formations isshown on the geologic map.
<br />Quntenenry alluvium is present in most of tdre streaal bottoms and
<br />on adjacent flood plains. Soil and pediment deposits cover large
<br />parts of the Wren. Lnndsiide debris surrounds the mowttains.
<br />MESOZOIC ROC%R
<br />AOCKH OF CRETACSOIIH •OE
<br />TRINIDAD 9AHDBTONE
<br />The Trinidad sandstone (Hills, 1899, p. 2) of the Isfontnnn group
<br />(Eldridge, 1888, p. 93) cans first described soudrenst of Trinidad in
<br />the Elmoro quadrangle. Ifills divided the fot•mntiar into the lower
<br />and upper gS•inirlnd with n thickness of 75 feet. for the )over part
<br />rand 70 to 80 feet for the upper part.. Later he chnngerl fire name to
<br />Trinidad sandstone (Hills, 1001, p. 1), but retained the snore forma-
<br />tional boundaries. Lee (1917, p. 48) redefined the formation by
<br />assigning the lower Trinidad to the Pierre shale rand by ref pining the
<br />upper Trinidad ns the Trinidad sandstone. In general, recent reports
<br />by the Geological Survey have followed Lee's definition of the
<br />Trinidad sandstone.
<br />The formation is 45 feet thick southeast of Trinidad, rand it increases
<br />in thickness tcesttcurd to 260 feet nenr Stonewall car the western
<br />margin of the coal field. However, the formation ranges in thickness
<br />from a thin edge at the northwestern edge of the coal field, where it
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