kmmo.ns.) THE WASATCH MOUNTAINS. 383 



The post-Archean transgression is here, as elsewhere, most distinct 

 and easily recognizable, and the positions winch the succeeding sedi- 

 mentary beds bear to the niassives of ancient crystalline rocks, show 

 that they must have been deposited on the flanks of lofty and precipi- 

 tous mountain masses. Of the rocks which were first deposited against 

 these shores the ontcrops are very limited and have been but slightly 

 studied. The great thickness of Paleozoic beds, which form the prin- 

 cipal mass or main crest of the range, rest upon the projecting nias- 

 sives of Archean rocks; not in regular folds with parallel axes, as in the 

 Appalachian system, but wrapping around (hem, with curving strike 

 and ever-changing dip. in anticlines and synclines with axes of varying 

 trends, which, on the eastern thinks of the range, are still partly buried 

 beneath the beds of the Tertiary transgression. 



The movement at the close of the Paleozoic is proved by no discern- 

 ible angular discrepancy in the position of beds deposited before and 

 alter it, but by the change in the character of sedimentation and by 

 the striking fact that the crest of the range marks the western limit of 

 deposition of Mesozoic beds in this latitude. From the meridian of 

 this range (112° W. long.) to long 117° 30' W. (from Greenwich), no 

 trace of .Mesozoic beds has been found, and those that exist west of 

 the latter are of entirely different character, both lithological and pal- 

 eontological, from those found east of the Wasatch range. 



The transgression about the close of the Jurassic is shown by a dis- 

 crepancy of strike rather than of dip, and even this, in the Wasatch 

 mountains, is not very marked but is well developed further east, espe- 

 cially in the Rocky mountains of Colorado. M A considerable thick- 

 ness of bower Cretaceous beds is found to the north, in British Colum- 

 bia (Kootanie beds), and in Texas, east of the mountains and south of 

 the Great Plains (Comanche beds), which are wanting in the Wasatch 

 and in Colorado. 



The transgression at the close of the Laramie (coal-bearing) Creta- 

 ceous is the most distinctly marked and most readily observed, next to 

 that at the close of the Archean. It is generally (though not always) 

 shown by a marked unconformity of angle between the Laramie and 

 succeeding deposits. The earlier deposits with unimportant exceptions 

 are marine, the Laramie brackish water, and all succeeding deposits in 

 the interior of the Cordilleran system of fresh water origin. 



In the Wasatch region the succeeding Eocene Tertiary conglomerates 

 overlap the eroded edges of all the earlier series, and even rest upon 

 denuded Archean high up on the western slopes of the range. They 

 generally constitute the greater portion of the high table lands or mesas 

 which form the eastern and southern continuation of the Wasatch 

 uplift. 



The Tertiary transgression, or transgressions (for there have been 



