The Sierra Nevada Range 



173 



the entrance to Yosemite National Park. The river cuts across 

 a series of thin beds of chert (metamorphosed siliceous sea- 

 bottom ooze) and shale that are compressed into astonishingly 

 intricate labyrinthine wrinkles. On the scoured and polished 

 rocks in the river bed these wrinkles conspicuously appear (Fig. 

 55). In the granitic areas above the lower Sierra slope occur 

 here and there small bodies and individual slabs of metamorphic 

 rock, remnants of the ancestral rock roof. Larger masses of 



Photo by F. C. Calkins, U. S. Geol. Survey 

 FIG. 55. Upturned beds of slate and schist. In lower Merced Canyon. 



metamorphic rock, including white marble, occur near May 

 Lake at the base of Mount Hoffmann, and also in the rugged 

 headwater basin of Yosemite Creek. Next to the broad belt 

 on the lower slope of the Sierra Nevada the masses of meta- 

 morphic rock, remnants of the ancestral rock roof, situated 

 near the crest of the range are the most extensive. They make 

 up the bulk of Mount Dana, Mount Gibbs, and Parker Peak, 

 and of that jumble of mountains north of Tioga Pass, the cen- 

 tral summit of which is Mount Warren. 



