| OCR Text |
Show 81 of the Jurassic gypsum to the valley- level, the fault amounts to a thousand feet. At the junction of the two, the evidence of faulting is to be seen in the vertical Fie*. 5- View of a " Jurassic" anticlinal, looking north: 0, Gallinas Creek ; j , Jurassic beds, com posed, from above downward, of the white gypsum, the yellow, and the red beds; 1, Cretaceous No. 1, sandstone; 3, Cretaceous No. 3, in the distance. escarpments of the middle bed of Triassic sandstone, which is here on edge with the deep- red marls on both east and west sides of it. The gypsum does not descend to the valley- level, however; the end of the anticlinal having been cut transversely by a line of drainage, marked in summer by a deep arroyo, ( Fig. 5.) Immediately to the west, the sandstone of Cretaceous No. 1 forms the usual line of hog- backs, but at this point it does not lie immediately on the Jurassic, the softer lower beds having been cut out by the passage of the Gallinas Creek. This stream cuts through the hog- back escaping from the valley of No. 2, and returns to it again, after pursuing a short course between No. 1 and the gypsum. Southward five miles, the Triassic beds with the sandstone cap have been lifted to a greater elevation, of at least 1,000 feet above the level of the Gallinas. This has naturally been accompanied with a greater lateral extension. In Plate III, the foreground consists of its red beds and intercalated sandstones which extend to the valley of the Gallinas; the Jurassic beds being undiscoverable on its flanks, and even Cretaceous No. 1 being lost for a short distance. This projection or angle is opposite to an isolated mass of this formation, which, in the absence of another name, I called Red Peak. The area of the Trias is concentric with its base, the boundary retiring eastward on the south side. Here the Jurassic beds re- appear, the gypsum standing vertical, and forming a line of narrow, steep hills; the lower beds are not visible, but form the bottom of a valley which separates the Jurassio hills from the mountain. The relation of the two formations is here clearly seen, ( Fig. 6.) The elevation of the red peak and adjacent mountain- axis has fractured the Triassic beds, so that the upper sandstone, which is horizontal on their summits, also lies at a steep angle ( 45°) on their southwestern flanks. An interesting example of curved strike is here exhibited. The tilted sandstone at the left of Fig. 7 strikes northwest and southeast; the same ledge in the middle foreground north and south. These beds lie immediately on the blood- red Triassic marls, as in the mountains and elsewhere. Two miles south the Jurassic and Cretaceous No. 1 beds disappear through the erosion of a drain age- valley, but south of the latter the Jurassic rises steeply, with a dip northwest 25°, to an elevation of 700 feet above the valley. The upper surface is composed exclusively of the gypsum, and the eastern is precipitous, exhibiting the usual three strata of white, yellow, and red in descending order. But below these appear the deep- red marls of the Trias, which occupy the valley separating the Jurassic hill from the Trias mountain, and form a body of Triassic bad lands. The surface of this tract is eroded into cafions, ravines, and arroyos, with irregular masses of a deep- red color between them. Perhaps three- quarters of a mile separates the vertical sides of the valley; the Triassic beds forming the eastern wall, with the marl below and a very heavy bed of hard sandstone on top, rising to 900 feet by barometer. In the bad- land tract I obtained satisfactory evidence of the lacustrine character of the formation, a point of much importance, inasmuch as the character of these beds has remained very obscure up to the present time. The evidence consists of numerous specimens of species of Unto from a number of distinct localities, and fragments of bones and teeth of two or three species of Saurians, one of which at least is of terrestrial habits, according to our present knowledge. I have submitted the Unios to my friend Mr. F. B. Meek, who informs me that they belong to three species, which he describes as follows: |
