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Show 78 Creek, near Conejos, contain pebbles of qnartzite, sandstone, trachyte, and basalt, indicating the existence of the latter as rocks during the deposit of the marls. At other points I observed a horizon of basalt, intercalated with the arenaceous marly beds, while the third horizon is the usual one, capping the marls, and giving the mesa char-actor to the region where it occurs. CHAPTER V. THE SIERRA MADRE ASD ITS WESTERN SLOPE. The close of the second chapter described the first appearance of the variegated red and yellow beds, as the exploration was carried from the valley of the Bio Qrande to the dividing axis of the Sierra Madre.* As these strata rise, forming large hills on the north side of the Rio Charaa, the road, rising less rapidly, passes over lower horizons, finally reaching a bed of hard, light, and rather coarse sandstone. At this point the route turns to the northward, leaving the river, and climbs a low, long hill, whose surface is this sandstone, without soil. A few miles beyond the summit is reached, and is fonnd to present a sage- brush plane, many miles in extent, which is bordered by hills of remarkable beauty. To the south the cafio nof the Chama with the Abiqnin Peak and other mountains beyond it bound the plane; while to the east and north, the brilliantly- colored strata above described form a perpendicular wall of about 500 feet elevation. The upper third or more of this precipice is of a lemon yellow, the remaining and lower portion of a subvermilion red, forming a beautiful combination. The rock is fissured by ravines, and intervening portions rise as huge buttresses of varied proportions, sometimes especially prominent near the summits, forming often regular bastions. Near the base certain bluish strata form naked mounds and hills of bad- land character; but I failed to discover any fossils on them. The southern face of this wall presents a tremendous fissnre, the " puerta " of the Cafion Cangilon. Our route laid through this defile for many miles, and we thus obtained an excellent section of the higher level of the region. The yellow beds or the present description were described at the close of chapter III, as being overlaid with a shale, and this again by an arenaceous conglomerate. These formations increase in thickness northward, and near the mouth of the canon Cangilon a bed of fractured gypsum appears above the shale; the former soon becoming 25 feet in thickness, the latter only 3 feet. Along the sides of the southern part of the canon the gypsum forms a snow- white bed of 50 feet in thickness, overlying the walls of yellow and red, and its borders are cut into fissures by the atmospheric erosion. From these points the stain produced by the dissolved gypsum forms stripes or fan- shaped shades of a beautiful mauve tint, which gives these rocky walls the appearance of a changeable silk, the mauve representing the shadows, and the red and yellow the lights. Altogether the picturesque forms, brilliant hues, and regular cleavage of the precipices which for miles bound this canon form a scene of unusual beauty. The beds soon present a northwest dip. The gypsum descends from its elevated position, and a mud- brown Bandstone appears on the summit of the walls. Six or seven miles beyond the mouth of the cafion, the gypsum bed is at the level of its bottom, forming low rounded hills at the base of the sandstone cliffs, ( see Fig. 4,) which rise to a height of 700 feet. From this point the bottom of the canon slowly rises between the sandstone walls, which, continuing their northwest dip, add perhaps 150 feet of thickness before the road reaches their summit- level. The road issues from the cafion on to an elevated country, which is covered with more grass than the regions previously traversed, and. large patches of sage- brush. A short distance from this point a line of low hills runs parallel to the direction of travel, with a northwest and southeast strike. They support groves of pinones, and examination showed that they form the outcrop of the bed of Cretaceous No. 2, and doubtless rest immediately on the sandstone below. They consist of lead- colored shales, which whiten on exposure, and contain Inoceramiis and 08trea in abundance. Having determined this horizon, I recur to those previously described, with the view of identifying them with the standard of comparison selected in chapter I, viz: the section at Colorado Springs. The resemblance is at once seen to amount to an identity. The sandstone of the northern half of the cafion Canjelon is the Cretaceous No. 1; thickness 800 feet; below it the gypsum is that usually referred to the Jurassic, 50 feet, and doubtless inseparable from the brilliantly- colored beds below, ( 400 feet,) which undoubtedly belong to the Jurassic beds. The hard sandstone underlying these is the upper member of the beds that correspond to the Trias of the same section. Their * The term " Sierra Madre" has been applied differently upon published maps of the Southwestern Territories. Its use is likely to be superseded as soon as the general topography of the several ranges and mountain groups shall have been determined. - |
