General Geology by Whitman Cross, assisted toy Arthur Coe Spencer. Economic Geology by Chester Wells Puriiigton. GEOGRAPHY AND PHYSIOGRAPHY. several of its branches have cut into or across the Banded Mountain is a term used in one or two which has been recently cut through a forest cov^ broken mesa, causing much diversity in the places by Holmes as an alternative for Hesperus ering into brecciated rock, in which erosion is now GENERAL RELATIONS. topography. Peak, but as the latter was finally placed upon proceeding at a rapid rate. Geographic position. The La Plata quadrangle Culture. - -The La Plata Mountains have been the Hayden map and was generally used through­ Bear Greek. The basin head of this stream is situated in southwestern Colorado, near the found to contain metalliferous deposits, and in the out the Hayden reports, the other name is applied overlaps the extreme head of the La Plata for 1^ State line, as is shown by the index map on development of mining operations a small town, to the summit of similar character north of miles and is excavated in the stocks of Diorite the title page of this folio. It is bounded by named La Plata, has grown up in the heart of the Mount Moss. Peak and Mount Moss and of the indurated and _ meridians 108° and 108° 15' west longi-o ExtentD . and. mountains. The Rio Grande Southern Towns, The other names on the map are those of local metamorphosed strata between them. Polished tude and parallels 37° 15' and 37° 30' drainage- Railroad crosses the quadrangle south usage as far as that could be ascertained. and striated areas in the upper part of the basin north latitude, embracing 237.22 square miles. of the mountains. Hesperus, situated show that this was the source of a local glacier, LA PLATA MOUNTAINS. Within its borders are the headwaters of the La at the crossing of the La Plata River, is the main but no considerable morainal accumulations exist Plata and Mancos rivers and of Bear Creek, an station within the area for the traffic from the Size and form of tlie group. The La Platas in the lower valley. Bear Creek enters the important tributary of the Dolores River. All of mountains and the valley below. Coal mining is form a compact group of high peaks, all the prin­ Dolores River in the Rico quadrangle, 8 miles this drainage is tributary to the Colorado River. carried on in the immediate vicinity of Hesperus cipal summits lying within a circle 9 miles in from the La Plata line, at an elevation of 7900 Relations to San Juan Mountains and the Pla­ on either side of the river. Agricultural lands, diameter, the center of which is situated in the feet. Fig. 5 represents the Sharkstooth, on the teau country. The quadrangle lies some 20 miles developed through irrigation, extend down the La Plata Valley near the mouth of Tirbircio west side of Bear Creek, the most northerly sum­ southwest of the San Juan Mountain front. In La Plata Valley from Hesperus, while in Thomp­ Creek. The lesser summits and outlying ridges mit of the La Platas. the intermediate space is a heavily timbered, hilly son Park and on the East Mancos are a number all come within an oval area 12 to 15 miles in Branches of Mancos River. The entire west­ country occupied by Paleozoic and lower Meso- of ranches. diameter. Nearly all the peaks of the inner circle ern slope of the mountains is drained by the three zoic formations. Westward the level expanse On the La Plata River at the entrance to the are situated within the La Plata quadrangle, but forks of the Mancos River, two of which penetrate of the Dolores Plateau stretches far toward the mountains is Parrott, once the county seat of La a few lie beyond its eastern border, in the Durango at their heads within the inner circle of peaks. canyon of the Colorado. On the southwest, and Plata County, when it embraced the whole south­ quadrangle. Of these branches the West Mancos is the longer, rising nearly 2000 feet above that plateau, is the west corner of Colorado, but the town is now Many of the summits rise to more than 12,000 rising in Owen Basin under Mount Moss and famous Mesa Verde, dissected by the deep can­ reduced to a single inhabited house. The present feet above sea level, and the highest, Hesperus Hesperus, Babcock, and Spiller peaks, all of yons of the Mancos River and its tributaries, the boundary of La Plata and Montezuma counties Peak,' reaches an altitude of 13,225' Height , _ of. which exceed 13,000 feet in height. The extreme favorite fastnesses of the cliff dwellers. The quad­ traverses the quadrangle, following the watershed feet. The general character of the peaks- head of the West Mancos is shown in fig. 11. rangleo is thus situated on the border Border_ . line,. between the Mancos and La Plata rivers. mountains and of the valleys dissecting them may The East Mancos heads in Rush Basin, under between the well-watered and forest- l^Slns Geographic names. In the course of work be seen on the Topographic, Structure Section, Spiller Peak, an amphitheater corresponding to clad mountain region of the San Juan andplateaus- in the La Plata Mountains it became desirable and Illustration sheets of this folio. that at the source of the west fork of the river. and the arid mesa, plateau, and canyon country to have names for various peaks and ridges Drainage system. The La Plata Mountains The Middle Mancos is practically a branch of the which extends far into Utah, Arizona, and New hitherto nameless. In a few other cases it was are the result of a domal uplift which has been East Mancos, heading in minor streams on either Mexico. These relations are brought out by figs. found that local usage was conflicting or for dissected by erosion. Consequently Domedis= side of the Hogback. 1, 2, and 3 of the Illustration sheets, to which some reason undesirable. Since in the drainage system of the mountains Eastern drainage. As shown by the topo­ Revival of streams- further reference will be made. these instances there were names earlier has a general radiate arrangement. graphic sheet, the two principal branches of Light­ names. Physical features. By virtue of its position, already applied in earlier publications But the work accomplished by the various streams ner Creek rise on the eastern side of the higher described above, the La Plata quadrangle presents concerning the La Platas, these older terms have has not been equal. The master stream is the La peaks of the La Platas. From Eagle Pass north varied physical features, typical of the broad, been revived. Plata, which, flowing south, has cut back at its to Cumberland Peak, which is just beyond the level, canyon-dissected plains to the west, and of The name Rampart Hills, applied to the prom­ head almost to the northern rim of the group, eastern margin of the quadrangle, are a number the foothills of the San Juan Mountains, but the inences due to the porphyry sheet on the eastern dividing the mountains into nearly equal parts. of small branches of Junction Creek. But while most prominent element in the topography is bank of the West Mancos Canyon, needs no The main northern stream, Bear Creek, has also Lightner and Junction creeks have cut back to the rugged La Plata Mountain group, occupying explanation. As seen from the west these por­ penetrated the inner circle of peaks, overlapping the main eastern divide of the mountains, there is the greater part of the northeastern section of the phyry cliffs present the aspect of an outlying the La Plata, a narrow divide separating the but a single summit of importance isolated by area. These peaks form one of a number of iso­ breastwork of the mountains. The long ridge basins at the heads of these streams. this erosion from the other high summits of the lated groups, rising high above the gen­ leading north from the La Platas to the Rico On the west side two forks of the Mancos have group. This is Bald Knob (11,600+ feet), situa­ eral plateau level, which are scattered Mountains Mountains was the course of an old Indian trail, cut slightly into the core of the group, leaving ted east of Baker Peak, about one-half mile east of over thet adjacent-i. portions otP/-II Colorado, T boneofanum-aetre°f * - s which in several places has been worn deep in but a jagged crest between their headwaters and the quadrangle line. While Lightner and Junc­ Utah, Arizona, and New Mexico. From the soft sandstones of the La Plata formation. the La Plata drainage. On the east the attack of tion creeks have but short courses Great , erosion the western summits of the La Platas may be This line of communication appears to have been the radial streams has been less effective, but within the physiographic limits of the j^jSnctfon seen the Rico, El Late, Carriso, Abajo, La Sal, a favorite one for the Indians of the region, and several branches of Lightner and Junction creeks La Plata Mountains, they have done a and, in the far distance, the Henry Mountains, all the name Indian Trail Ridge is applied to the head on the slopes of the highest peaks. These greater amount of work than the forks of the mountains of analogous origin. divide followed. The names "Sliderock" and streams are tributary to the Animas River.