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Show 173 APPENDIX H2. REPORT ON THE GEOLOGICAL AND MINERALOGICAL CHARACTER OF SOUTHEASTERN CALIFORNIA AND ADJACENT REGIONS. UNITED STATES ENGINEER OFFICE, GEOGRAPHICAL SURVEYS WEST OF THE 100TH MERIDIAN, Washington, May 13, 1876. DEAR SIR : I have the honor to submit herewith a report upon the geological and mineralogical conditions of Southeastern California and adjacent regions. The country traversed by the party in command of Lieut. Erio Bergland, Corps of Engineers, our able and beloved leader, along the Mohave River, across the Opal, Payute, and Dead Mountains, to Cottonwood Island, in Southern Nevada, thence to the mouth of the Virgin River, across the Colorado to the Cerbat and Blue Ridge Mountains in Northwestern Arizona, from there to Fort Mohave and along the Colorado River to the Mohave range, Monument, and Riverside Mountains, thence to San Bernardino, via Chucka-valla Peak, Coahuila Valley, and San Gorgonia Pass, was of unusual interest in geological, mineralogical, aud chemical respects. Nor of less interest was the trip made, in accordance with your orders, by myself alone ( after the return of the expedition to LOH Angeles) to Panamint, Darwin, Owens Lake, Cerro Gordo, Benton, Aurora, and Virgiuia City, Nev. An immense area was thus visited from June to November, and valuable collections made. The chemical analyses of rocks, soils, and mineral springs necessary iu connection with my reports were made in the laboratory of the Smithsonian Institution ; and I cannot but express my deepest thanks to the Secretary, Professor Henry, for the liberal spirit he has shown in giving me the free use of the laboratory and all necessary utensils and chemicals wheuever I desired. Very respectfully, your obedient servant, OSCAR LOEW. Lieut. GEO. M. WHEELER, Carps of Engineers, in charge. CONTENTS. The Primitive formation- The Palaeozoic formation- The Mesozoic formation- The Tertiary formation- The Quaternary formation- Freshwater lakes of Ae Quaternary period- Black coating of rocks- The Eruptive formation- Earthquakes- General geological history of Southern California- On the metalliferous veins of California- Analysis of the tin ore of Timescal- Analysis of Partzite. Taking a bird's- eye view of the great area between the Lower Colorado and the gigantic mountain- chains traversing California from north to south, ( the Sierra Nevada and its southern prolongations, the San Bernardino and Jacinto Mountains,) one cannot fail to recognize at once a considerable predominance of three formations, viz: the Primitive, the Eruptive, and the Quaternary. A subordinate position is occupied by the Palaeozoic, the Mesozoic, and Tertiary. While the numerous ranges of hills aud mountains mainly consist of granite or trachytic rocks, the intervening valleys are filled by Quaternary deposits. The topographical features of the Mohave Desert differ, therefore, vastly from those of the Painted Desert in Northeastern Arizona, a realm of sandstone, with the characteristic mesa-type of the table- lands. THE PRIMITIVE FORMATION. Nearly all the prominent ranges of Southern California belong to this formation, although in a number of instances the axial rock is concealed, as at the Opal Mountains, by Palsezoic strata, at the Blue Ridge Mouutains by volcanic flows. The San Jacinto Mountains, the most southern range of California, consist chiefly of granite, well exhibited iu the precipitous faces turned toward the east. It is of dense structure, hard, and a splendid building stone, resembling closely the New England granite. Of mica, it is the black variety ( biotite) that dominates in the rock, and among the accessory constituents titanite, tnrmaliue, and garnet deserve especial notice. The titanite* is disseminated in small yellowish crystals through the rock for over 30 miles, ( Whitewater to Los Toros,) while the latter two minerals are confined to narrower limits, ( near Whitewater.) * Titanite is also found in the granite of the Sierra Nevada, especially on the Moke-lumne and American Rivers, according to Prof. W. P. Blake. |