HISTORY OF DEFORMATION IN GREAT Bt^SIN PROVINCE 247 



horizontal, showing that this period was not one of very great disturb- 

 ance. Nevertheless there was probably some local folding and consider- 

 able uplift and subsidence on a large scale. Some of the folds and faults 

 which had been previously formed continued their growth. 



In the Death Valley region the earlier Tertiary plications became 

 more marked, as shown by the upturning of probable Pliocene strata. 

 At Twin springs, in the Pancake range, and in the Meadow Valley can- 

 yon the writer noted in Pliocene strata faults which are not so recent as 

 those presently to be described as Pleistocene, since the}^ are not ex- 

 pressed in the topography. It is possible that some of the larger folds, 

 such as the anticlinal of the Mormon range, originated in the Pliocene. 

 In Utah, Nevada, and the Great Plains region King has described an 

 important broad tilting of the Pliocene strata.^ 



According to Mr Diller, the Sierra Nevada experienced at the close of 

 the Pliocene a great elevation, accompanied by great volcanic activity .f 

 This was followed by the erosion which wrought the present grand 

 scenery of this range. 



In the Colorado plateau the Grand canyon began to be cut, in conse- 

 quence of the general deformation.^ 



PLEISTOCENE 



During the Pleistocene period local deformation has been compara- 

 tively active. Mr Gilbert has described and admirably discussed the 

 many recent fault-scarps with vertical displacements of 100 feet and less 

 which have been formed since the lake Bonneville epoch. § Farther 

 west, in the lake Lahontan basin. Professor Russell has discovered similar 

 recent fault-scarps of about the same magnitude. || In Meadow Valley 

 canyon the present writer has observed post- Pliocene flexures and faults, 

 some of which are so recent as to be directly expressed in the topography.^y 

 In the Funeral Range region the folding, which became active during the 

 Tertiary, continued until it involved the probably Pleistocene basalts. 



Besides absolute folding and faulting, there has been much warping, 

 as is shown in the region north of lake Mono, where the sediments of 

 the Pliocene Shoshone lake have probably been elevated 1,000 or 1,200 

 feet above their normal height, in conjunction with Pleistocene volcanic 

 activity. This deformation is of the same important kind as that which 

 Mr Gilbert recognized in Utah, where the Bonneville shorelines have ex- 



* Explorations of the Fortieth Parallel, vol. i, p. 757. 



t Eighth Ann. Rept. U. S. Geol. Survey, part i, p. 432. 



X C. E. Dutton : Second Ann. Rept. U. S. Geol. Survey, p. 120. 



§ Monograph i, U. S. Geol. Survey, pp. 340, 352, 354, 356, 301, 305, 367, 308, 371, 372. 



II Monograph xi, U. S. Geol. Survey, pp. 25, 27, 29, 274-283. 



II See figure 1, plate 24. 



