250 GEOLOGY. 



and many species and genera were exterminated. The distinct 

 fauna that made its appearance during the Quaternary originated 

 some time during this transformation of the Pliocene into the gla- 

 cial epoch. 



During the closing centuries of the Pliocene epoch, some convul- 

 sive movements occurred further west. King remarks " that the 

 whole country from about 114 30' was depressed to the west, the 

 western edge of the Pliocene lake settling 2,000 feet." * * * 

 " The same is true from Thousand Spring Valley eastward to Cache 

 Valley, and to the base of the Wasatch, which is a region of recur- 

 rent faults." * * "I consider it proved that the displacement at 

 the eastern base of the Sierras, and the western base of the Wasatch T 

 occurred at the close of the Pliocene, and thus broke the one broad 

 lacustrine basin into two new lake basins one at the foot of the 

 Sierras, the other under the shadow of the Wasatch Range which 

 were to receive the waters of the quaternal age." Thus it appears 

 that as the Miocene closed with the production of fractures and 

 fissures that covered a vast area with lava, so the closing centuries 

 of the Pliocene were characterized by great vertical displacements 

 of mountain chains. 



General Remarks on the Tertiary. Many of the strata of the 

 Miocene deposits were specially favorable for the preservation of 

 animal remains. Some of the strata of the Pliocene, in at least a 

 few localities, were scarcely less adapted to such a purpose. The 

 perfect petrifaction of many of these remains also indicates that this 

 property was possessed by these waters in an eminent degree. The 

 mammalian skeletons must have been carried into the old lakes 

 during flood time from some of the low lands that were subjected 

 to overflow, and once in the quiet, muddy bottom of the lake, were 

 soon covered by sediments that preserved them to our times. The 

 very original sharpness of the outline of these remains have been 

 preserved. Seldom are any marks of erosion detected on any of 

 the specimens. The curious feature about these remains is that few 

 representatives of any sub-kingdom of animals, except the verte- 

 brates, have been preserved, and of these no classes but mammals 

 and birds, except a few species of turtles. No fishes have yet been 

 found, and only a few mollusks, and these, except a land snail, of 

 comparatively low type. Fish and mollusks could not have existed 

 extensively in these lakes, or else their remains would have been 

 preserved. The climate certainly was favorable to amphibious 



