OCR Text |
Show 175 acquires an especial interest on acconnt of rich metalliferous lodes being associated wirh it. At the saline flats of the Mohave ( Soda Lake, Mohave Sink) the Palaeozoic limestone is highly crystalline and siliceoas, composes hills and mesas 30 to 40 feet in height, and its strata dip at an angle of 30° to the west. THE MESOZOIC FORMATION. On the entire trip through Eastern California cretaceous fossils were not seen, but a deep- red sandstone, that probably has to be referred to the Upper Carboniferous or Trias, as it forms close connection with the Palaeozoic strata, was encountered in a few places, viz, the Opal Mountains and the northern spurs of the Black Cafion range, north of the deserted Mormon town Callville, in Southern Nevada. Tliis sandstone, accompanied by gypsum, is exposed again opposite the mouth of the Virgin River, and appears to continue beneath the surface of the great detrital valley to the Cerbat range. THE TERTIARY FORMATION. This formation probably is wide- spread in the Mohave Desert, but hidden by the extensive Quaternary deposits. In the valley of the Mohave River thick beds of sandstone, clay, and conglomerate are exposed, whose Tertiary age was recognized by Prof. Jules Marcou.* Grauite and quartzite contributed the pebbles to these conglomerates, and as the volcanic rocks, notwithstanding their great abundance all along this valley, do not participate, it is evident tbat their protrusion took place after the deposition of the Tertiary beds, which latter exhibit uplifts and dislocations caused by the volcanic protrusions. These inclined strata are again overlaid by horizontal uudisturbed strata, of moderate thickness; as, for instance, 3 miles east of Grape- vine ranch ; also a singular bend noticed in the sandstone strata 10 miles east of Camp Cady may be due to volcanic perturbations. At Canon Springs, on the eastern slopes of the southernmost spurs of the San Bernardino range, occur strata evidently of equal age with those of the Mohave River valley, and consisting of light- red and gray sandstone, and indurated bluish clay with seams of gypsum. These strata show a highly- inclined dip to the south and southwest, and exhibit singularly twisted and warped folds. In the horizontal strata of conglomerate overlying them pebbles of basalt and trachyte occur, while none are seen in the inclined strata beneath them. FIG. 1.- Section at Canon Springs, San Diego County, California. a. Dark pink- colored sandstone, 80 feet. ^ b. Yellow sandstone, 24 feet. | c. Light- pink sandstone, 32 feet. S Tertiary strata. d. Yellow sandstone, 2 feet. I e. Gray sandstone iuterstratified with clay, 50 feet. J / . Post- volcanic strata. g. Granite. « ?. Intrusive rock, ( trachyte.) THE QUATERNARY FORMATION. The Glacial epoch, by which the Quaternary in high and moderate latitudes was introduced, has left but few markings in Southern California. At that time the country was submerged in the Quaternary oceau, and the highest peaks projected as merely small cliffs above the surface. Still the period of cold was not entirely gone when the gradually- rising country acquired considerable dimensions, and the peaks commenced to bear glaciers to a small extent, as the traces of moraines in the San Bernardino and Jacinto Mountains indicate. * Pacific Railroad Reports, volume 3. |