| OCR Text |
Show 79 thickness on the Chania was not determined. The feature of this section is the increased thickness of the beds of the Jnrassic and Cretaceons No. 1. FIG. 4.-- South wall of the canon Canjelon: c 1, Cretaceons No. 1; } j, gypsam capping tbe " Jurassic." Continuing the route, we reach a second line of low hills of yellowish soft sandstone with Ortrea, probably Cretaceons No. 3, and then descend into tbe shallow valley of Nntria Creek. From this point the level of the country rises to Tierra Amarilla, which was determined by the topographers to stand 7,480 feet above the sea. To the south and east of this town, high hills of yellowish sandstone present escarpments to the north, which are apparently Cretaceous No. 3, and contain numerous Inocerami. The Rio Chama flows two miles weBt of the town, in a south by west course, through a bed cut in the dark lead- colored shales of Cretaceous No. 2. Eight miles northeast an enormous vertical mass of rock rises abruptly 1,274 feet above the stream below its base, and is continued to the north and west in a less precipitous mountain- flank. This mass of rock is a landmark over a great extent of country; it is cleft to the base by the caftan of the Brazos Creek, one of the heads of the Chain a. I took occasion on my return to traverse this upthrust, taking the trail which leadB from Tierra Amarilla across the mountain- axis, of which it is the western border, to Conejos, on the edge of the Rio Grande Valley. The road follows the course of the Brazos River, and for some distance the Cretaceous beds are in sight and nearly horizontal. Near the precipice above mentioned, these are lifted into high bills at an angle of 70° and 80°. On the north side of the river, sandstones of No. 1 rise with a similar dip, forming the foot- hills of the mountain, which rises perpendicularly to 1,500 feet. This mass is largely composed of a dense breccia of qnartzite fragments, closely cemented into a uniform rock of a general pink color, and not variegated. Its characteristics and position refer it with probability to the Trias; but I could not detect any indication of the Jurassic beds between it and Cretaceous No. 1. After reaching the summit, we traversed the upturned edges of the formation, which have a strike varying from northwest and southeast to north and south. The elevated region now traversed by the trail is perhaps thirty miles in width, and is worn into rounded hills. The highest point indicated by the barometer is 10,400 feet. On the upper waters of the San Antonio Creek, high hills come into view, which have flat tops composed of a bed of trachyte, and their sides are often covered with pink and purple fragments of this rock. Within twenty miles of Conejos, the intervals between these hills are occupied by a heavy deposit of the Santa ¥ 6 marls, which, with masses of intrusive basalt rising in irregular masses, reminded us that we had once more reached the forbidding scenery of the Rio Grande Valley. The bluffs that border the Chama near Tierra Amarilla are, as before observed, composed of the shales of No. 2, and they contain abundance of oysters and Inocerami. Near the upper part of the series, there are several thin beds of a light- brown color, containing numerous broken fish- bones and Ostrea congesta, & c.; the appearance resembling closely fish- bearing shales found by Professor Madge near Stockton, Kans. From Tierra Amarilla, the route of my party lay southwestward. After crossing the river and the bluffs which bound its immediate valley five miles beyond it, the sandstone of Cretaceous No. 1 rises from beneath the Cretaceons No. 2 with a southeast dip. In some places, it rises abruptly like the wall of a fault, forming vertical bluffs of greater or less elevation, facing the east. This axis of elevation is at this point narrow, and the sandstone is soon found to dip to the southwest, west, and northwest. The route continued for forty miles along the western base of this line of elevation, which increases in importance as we proceed southward. A first, the Cretaceous No. 1 sand- |
