200 STEUCTUEAL GEOLOGY. 



we find that certain beds thin out shoreward. It is manifest in this case 

 that the waters of the lakes must have fallen or the land have risen. Again, 

 we find upper lake beds unconformable on lower lake beds. Here it is 

 manifest that a dry land period separated their deposition, and that displace- 

 ment occurred. These outthinnings, overlappings, and unconformities 

 appear from time to time from the base to the summit of all the fresh water 

 beds older than the Brown's Park. 



There are some other interesting facts relating to the belt under con- 

 sideration, viz, the appearance of many conglomerates which are rapidly 

 changed into sandstones in a direction farther from shore. These conglom- 

 erates are found to be made up of the more or less water-worn fragments of 

 limestones, sandstones, and quartzites similar to those outcroppings in the 

 mountain region or area of uplift, and often contain the same fossils, leading 

 us to conclude that they are derived from that region. 



It should be remarked here that the appearance of these conglomerates, 

 together with the overlappings, outthinnings, and unconformities before 

 mentioned, furnish the evidence on which we decide that this was the old 

 shore-line, and that the lake beds were never continuous over the great 

 Uinta area. On the other hand, the fact that no such phenomena have been 

 observed in the outcroppings of the Mesozoic and Paleozoic beds leads us to 

 conclude that they were at one time continuous over the Uinta area, and 

 this is strengthened by the fact that in all these lower groups any bed found 

 on the one flank re-appears on the other with all its lithologic character- 

 istics; and it is thus that we fix the epoch of the inception of the Uinta 

 upheaval after the close of the deposition of the Upper Hogback Sandstone 

 of the Point of Rocks Group, and before the deposition of the lowest bed 

 of the Bitter Creek formation. 



Returning again to the consideration of sedimentation in the region of 

 downthrow in its relation to displacement and degradation in the region of 

 uplift, we have first to consider the amount of sedimentation or building up 

 of the sediments on the flanks of the uplifts to the extent of many thousand 

 of feet ; next, the general unconformities which separate some of the forma- 

 tions ; and, lastly, the minor unconformities, overlappings, and outthinnings 

 observed in the zone of ancient shore-lines. From all these facts it appears 



