XVI REPORT UNITED STATES GEOLOGICAL SURVEY. 



great Eocky Mountain region, especially those portions of it that have 

 been surveyed, as well as those in which surveys are in progress. 



Among other important results, he has shown the identity of the 

 lignitic series of strata east of the Rocky Mountains in Colorado with 

 the Fort Union group of the Upper Missouri River, and also its iden- 

 tity with the great Laramie group of the Green River Basin and other 

 portions of the region west of the Rocky Mountains. He also finds 

 the planes of demarkation between any of the Mesozoic and Cenozoic 

 groups, from the Dakota to the Bridger inclusive, to be either very ob- 

 scure or indefinable; showing that whatever catastrophal or secular 

 changes took place elsewhere during all that time, sedimentation was 

 probably continuous in what is now that part of the continent from the 

 earliest to the latest of the epochs just named. Other results and further 

 details of the season's work will appear in the following paragraphs. 



The general course of travel i^ursued by Dr. White during the season 

 was as follows, not including the numerous detours, meanderings, and 

 side trips which the work necessitated : Outfitting at Cheyenne, he jour- 

 neyed southward, traversing in various directions a portion of the great 

 plains which lie immediately adjacent to the eastern base of the Rocky 

 Mountains in Colorado. The most easterly point thus reached was some 

 sixty miles east of the base of the mountains and the most southerly 

 point about twenty -five miles south of Denver. Returning to Denver to 

 renew his outfit, he crossed the Rocky Mountains by way of Boulder 

 Pass, through Middle Park. After making certain comparative exam- 

 inations of the Mesozoic and Cenozoic formations in Middle Park he pro- 

 ceeded westward to the headwaters of the Yampa River, following that 

 stream down to the western foot-hills of the Park Range of mountains. 



Here resuming his comparative examinations of the Mesozoic and 

 Cenozoic strata, he passed down the valley of the Yampa as far as Yampa 

 Mountain, one of those peculiar and remarkable up-thrusts of Paleozoic 

 rocks through Mesozoic strata. In all this area, as well as that between 

 the Yampa and White Rivers, the Laramie group reaches a very great 

 and characteristic development, and it received careful investigation, 

 yielding some of the most important results of the season's work. 

 Crossing the ground between the two rivers named to White River Indian 

 agency, thence down White River Valley about one hundred miles ; 

 thence to Green River, crossing it at the southern base of the Uintah 

 Mountains, making many detours on the way, he reviewed the geology 

 of the region which he had surveyed during the previous season. This 

 review brought out not only the important paleontological facts before 

 referred to, but it also added materially to the elucidation of the geological 

 structure of the region which lies between the eastern end of the Uintah 

 Mountain Range on the west and the Park Range on the east. 



Beyond Green River he pursued his travels westward, studying the 

 Mesozoic and Cenozoic strata that flank the Uintah Range upon its south 



