OCR Text |
Show 286 the Urac ridge would seem to indicate the mechanical origin of these deposits, though metamorpbism has entirely obliterated every other trace of their original character. The same metamorphic action may yet be found to have extended to the more recent formations which rest upon the flank of this great lateral spur. But the Cretaceous, as also the Tertiary beds, have been removed by the erosion of the valley of the Cimarroncito, so that the slope of the granitic ridge is barred, except perhaps insignificant outliers of inclined Cretaceous strata, which have escaped degradation, as if to afford a clew to their former extent and intimate relation to the subordinate axis of upheaval. Indeed, in the low ridge through which the Cimarroncito has cut its lower canon, and not more than a mile north of the Urac Mountain, the Tertiary sandstones are gently upraised, and bear unmistakable evidences of metamorpbism in their semi- quartzose character. Just beyond this point, at the foot of a charming grassy nook, through which the merry little stream winds in the descent of its bowlder- strewn bed, a picturesque escarpment of light granitic rock rises over the stream, forming a craggy battlement along its northern margin. So it would appear that we have already gained the threshold of that old igneous belt which had its seat of origin or culmination in Great Baldy, at the head of the Moreno Valley, twenty miles to the northwest- an outburst of igneous activity similar to, though less marked than, that in which originated the twin cones of the Spanish Peaks, to the north of the Purgatory. From the eastern flank of Great Baldy northward, the Tertiary deposits follow the somewhat irregular zigzag trend of the main watershed separating the drainage of the Canadian from the basiu of the Rio Grande, until reaching the Francisco Pass, at the initial point of the Baton Hills, on the northern boundary of the Territory, or about thirty miles in a direct line nearly due north of Baldy. To the east, the entire country is occupied by the Lignite formation, which is abruptly terminated in the lofty escarpments boundiug the valley of the Canadian. The Baton Hills form a broad- topped ridge, culminatiug in the watershed between the Purgatory, an affluent of the Arkansas, and the headwaters of the Canadian, and which attains an altitude of between 8,000 and 9,000 feet. From the point where it impinges upon the main range, it stretches nearly due east forty miles, and abruptly terminates amidst the wild ravines and pretty glades at the foot of the basaltic wall capping the Chicorica Mesa, in the neighborhood of the stage- road over the Baton Pass. From a high point near the summit of the pass, at an altitude of near 8,000 feet, the topographical features of the ridge and its relations to the great Tertiary plateau are advantageously displayed. The main divide perceptibly rises to the westward in rounded wooded heights; but to the south westward files of successively lower undulations or ridges appear, clothed with pine and a variety of dwarfish deciduous growth, marking the courses of the numerous drainagechaunels which traverse the plateau from their sources in its western border. Here, too, are observed those conspicuous terrace- like steps which are the records of early shore- Hues in the drainage of the ancient waters which occupied the region bordering the eastern flank of the mouutains during the epoch preceding our own. These benches- variable in height and distinctness of definition, often forming considerable escarpments or sharp declivities, according to the nature of the deposits, whether arenaceous shales or more consolidated sandstone, out of which they are wrought- constitute interesting features in the topography of the plateau, distinctively peculiar to this formation. Hence it is tbat when the great eastern escarpment is viewed from a short distance out in the plaius, the formation reveals |