OCR Text |
Show 110 * Looking from the Gallinas Mountains to the east' s ward a singular view meets the eye. The mountains ^ do not taper off gradually toward the plain, but, .2 where the spurs have fallen off to about one- third " § the mountain's height, a high ridge, steep in the ex- § treme, but of short extent, cutting the spurs of the « Gallinas Mountains at right angles and forming a 5" system of its own, stands prominently forth. The £ Gallinas River has cut a stupendous cafion through * these masses, which is uearly 2,500 feet deep. While • § syenite composes the principal mass of the Gallinas § Mountains, this strange elevation consists of fine' s grained granite containing red and white feldspar ^ and quartz, but relatively little biotite. This rock Q* also exhibits transitions into gneiss and grannlite. £ There can be but little doubt as regards the eruptive S character of this granite. The nearly perpendicular '^ faces of this hnge granite mass constitute it a land- * mark prominently visible far out on the plain. From J the north side the portion lying north of Gallinas u- Creek, called the Tecolote rock, may be easily climbed. _ Leaving the Canon of the Gallinas, we enter a mod' s erately wide valley, and, following it, after a journey 1 ^ of eight miles, reach the hot springs of Las Vegas. & g Some two miles above this place, however, the river • § " 8 passes another narrow canon about a mile long. At * lg the hot springs we again encounter the Carbonifer- © I ous, characterized here by the shells Productus and 13 Spirifer. Le Conte, usually a good observer, has overs' £ looked their existence when examining these regions " S^. as geologist of the Pacific Railroad survey. He re- • ^ marks, " No Paleozoic rocks are seen between the J 2 dark- red sandstones and the gneissoid rock, the Car- * j? bonifcrom limestone being here absent." I observed § Ja the Carboniferous limestone resting directly on the ^. S red gneiss, from whose fissures hot waters issue. S « The rock is sumewhat metamorphosed in contact ^^ with the gneiss, which latter is undoubtedly erupt- . § 8 ive, as indicated by the bends and displacement of " Z & the limestone. The space left by the partially ino- 28 perfect contact of the limestone with the gneiss is * I tilled with a thin stratum of clay, from which efflor-jg\ § esccnees of alum develop. This is due to the per-g" g colating mineral- water, which contaius, besides snl- * t J pbate, carbonate, and chloride of sodium, a trace of § : § sulphureted hydrogen- a trace so small, however, 5 a that it is hardly perceptible by the odor; still, it O gives rise to the formation of sulphuric acid by j » undergoing oxidation, and, as the next consequence, *•• the formation of alum and gypsum when this acid • 2 comes in contact with clay or limestone. • § Passing from the hot springs eastward)}* along the Js river there is a fine exhibition of the sedimentary Z strata, all, nearly, in a vertical position, extending i about half a mile, and terminating upon entering 3 the plains three miles north of Las Vegas. The Car' s, boniferous limestone is followed by alternate layers J of slate and shale, then ( 3) gray sandstone, ( 4) red, 5 fine- grained sandstone, ( 5) limestone, ( 6) gray sand-g* stone several hundred feet thick and widely project- *£ ing, and thus turning the river at right angles for J § some 50 feet; this rock shows beside the normal " stratification a second and false one: ( 7) slate, ( 8) J sandstone, ( 9) shales, ( 10) sandstone. g East of No. 10 all the strata have a horizontal posi- <* tion, and are of Cretaceous age, the predominating J: fossil being Inoceramus problematicu*. The scarcity r£ of the other fossils is in strange contrast with the £ abundance of this species. Should there be a certain connection between the nature of the limestone and the specific kind i f shells contained in it f This limestone is an argillaceous one. |