DSC 19 mo 



THE PLEISTOCENE GEOLOGY OF THE SOUTH 



CENTRAL SIERRA NEVADA WITH ESPECIAL 



REFERENCE TO THE ORIGIN OF 



YOSEMITE VALLEY. 



BY HENRY WARD TURNER. 



(Published by permission of the Director of the United States Geological Survey-) 



CONTENTS. 



I. 



II. 

 III. 



IV. 



Plates XXXI-XXXIX. 



Page. 



The Pre-Pleistocene Orogenic History of the Sierra 



Nevada 262 



Orogenic Movements in the Pleistocene 267 



Pleistocene Periods 269 



1. The Sierran Period 269 



2. The Glacial Period 269 



Glaciation of the Inyo Mountains and of the South- 

 ern Sierra Nevada 273 



3. The Recent or Post-Glacial Period 275 



The Origin of Yosemite Valley 275 



1. General Statement 275 



2. Views of Previous Observers 278 



3. Erosive Power of Ice 284 



4. Rock Basins 286 



5. Glacial Cirques 289 



fohnson's Theory 290 



6. Cause of the Glacial Period. 293 



7. Evidence of Two Periods of Glaciation 294 



Evidence of Two Ice Periods in the Sierra Nevada. . 297 



8. Evidence of Glaciation in Yosemite Valley 302 



9. Area Covered by the Yosemite Glacier 305 



10. Geological Formations about the Valley 30S 



11. The Joint Systems of the Valley 309 



Vertical Joints 310 



Inclined Joints 311 



Horizontal Joints 312 



Relation of Joints to Schistosity 312 



12. Formation of Domes 312 



13. Formation of the Valley Floor 315 



14. Conclusions 316 



Table of Illustrations 321 



[261] 



November 3, 1900. 



