Annual report of the United States Geological Survey to the Secretary of the Interior . ardanelle Cone. The lavas of these bluffs are, to a considerable extent, massive,basaltic looking rocks. At the northwest base, south of HighlandCreek, there is also some rhyolite. The andesite breccias are here, as elsewhere, abundant. They are ingeneral roughly stratified. A view taken of the andesite ridge northof the road from the Big Trees to Markleeville is reproduced in , A, and shows the imperfeel stratification. In the neighbor-hood of the Highland Lakes there are numerous bowlders of grani
Annual report of the United States Geological Survey to the Secretary of the Interior . ardanelle Cone. The lavas of these bluffs are, to a considerable extent, massive,basaltic looking rocks. At the northwest base, south of HighlandCreek, there is also some rhyolite. The andesite breccias are here, as elsewhere, abundant. They are ingeneral roughly stratified. A view taken of the andesite ridge northof the road from the Big Trees to Markleeville is reproduced in , A, and shows the imperfeel stratification. In the neighbor-hood of the Highland Lakes there are numerous bowlders of granite inthe andesite, one of which is shown in PI. XXXVI, B. This is from aphotograph taken a little southwest of the Highland Lakes. In thesame vicinity there are dikes of light-gray hornblende-andesite cuttingother dark-colored andesitic masses. On the summit of Arnot Peak,which has an elevation of 10,000 feet, the lavas are chiefly or entirelyandesite, some of which, in the form of tuft, is distinctly Stratified. The U. S. GEOLOGICAL SURVEY SEVENTEENTH ANNUAL REPORT PART I PL. XXXVI. A. RIDGE OF NORTH OF THE BIG TREES ROAD IN ALPINE COUNTY. B. GRANITE BOWLDER EMBEDDED IN ANDESITE-BRECCIA. TURNER.] THE DARDANELLES AREA. 709 breccia mountains along the crest of tbe range just south of SonoraPass likewise are arranged in layers. Glacial markings were noted everywhere above an elevation of 7,000and below 10,000 feet, giving evidence that a nearly continuous icesheet covered all the upper part of the range, only rugged peaks andridges projecting above it. There must have been movement in thisice sheet, even on the very summit of the range. Thus, in the sag ofthe divide, 2h miles northwest of Tower Eock, through which a trail toBridgeport passes, glacial polish and stria? may be s«en, indicatingmovement both east and west—that is to say, the stria? extend acrossthe dividing line of the drainage easterly to the Great Basin and west-erly to the Pacific. There is a s
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