I30 



NATURE 



[Dec. 13, 1877 



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 identity 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 demarcation between any of 

 the niesozoic and cenozoic groups, from the Dakota to the 

 Bridger, inclusive, to be either very obscure or inde- 

 finable ; 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 earhest to the latest of 

 the epochs just named. 



The general course of travel pursued by Dr. White 

 during the season was as follows, not including the nu- 

 merous detours, meanderings, and side trips, which the 

 work necessitated. Outfitting at Cheyenne, he journeyed 

 southward, traversing in various directions a portion of 

 the great plain which lies immediately adjacent to t>^e 

 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. Return- 

 ing to Denver to renew his outfit, he crossed the Rocky 

 Mountains by way of Boulder Pass, through Middle 

 Park. After making certain comparative examinations of 

 the mesozoic and cenozoic formations in Middle Park, he 

 proceeded westward to the head-waters of Yampa River, 

 following that stream down to the western foothills of the 

 Park Range of mountains. Here, resuming his compara- 

 tive examination 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 upthrusts 

 of palaeozoic 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 100 miles, thence to 

 Green River, crossing it at the southern base of the 

 Uinta Mountains, making many detours on the way, he 

 reviewed the geology of the region which he had sur- 

 veyed during the previous season. This review brought 

 out not only the important palsontological facts before 

 referred to but it also added materially to the elucidation 

 cf the geological structure of the region which lies 

 between the eastern end of the Uinta 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 

 Uinta range upon its south side, and making comparisons 

 of both their lithological and palccontological charac- 

 teristics. 



In this way he traversed the whole length of the Uinta 

 range, crossing at its junction with the Wasatch range 

 over into the valley of Great Salt Lake. Re-crossing the 

 Wasatch to the north side of the Uinta range, he con- 

 tinued his examinations of the cretaceous and tertiary 

 strata into and entirely across the Great Green River 

 basin, leaving the field at the close of the season at 

 Rawlin's station on the Union Pacific Railroad. 



A general statement of the results of the season's work 

 has been given in a previous paragraph, but the following 

 additional summary will make the statement somewhat 

 clearer, being made after the route of the season's travel 

 has beeii indicated. The formations of later mesozoic 

 and earlier cenozoic ages, especially those to which Dr. 

 White, in former publications, has applied the provisional 

 designation of " post-cretaceou?," have received par- 



ticular attention. The extensive explorations or' \iv. 

 Hayden in former years, and the palseontological in- 

 vestigations of the late Mr. Meek, pomted strongly 

 to the equivalency of the Fort Union beds of the 

 Upper Missouri River with the lignitic formation 

 as it exists along the base of the Rocky Moun- 

 tains in Colorado ; and also to the equivalency of the 

 latter, with the Bitter Creek series west of the Rocky 

 Mountains. The investigations of the year have fully 

 confirmed these views by the discovery not merely of one 

 or two doubtful species common to the strata of each of 

 these regions, but by an identical moUuscan fauna ranging 

 through the whole series, in each of the regions named. 

 This shows that the strata just referred to all belong to 

 one well marked period of geological time ; to the strata 

 of which Mr. King has applied the name of " Laramie 

 group" (Point of Rocks, Group of Powell). His in- 

 vestigations also show that the strata which in former 

 reports by himself and Prof. Powell, have been referred 

 to the base of the Wasatch group, also belong to the 

 Laramie group, and not to the Wasatch. He has reached 

 this later conclusion not merely because there is a simi- 

 larity of type in the fossils obtained from the various 

 strata of the Laramie group with those that were before 

 in question ; but by the specific identity of many fossils 

 that range from the base of the Laramie group up, into, and 

 through the strata that were formerly referred to the base of 

 the Wasatch. Furthermore some of these species are found 

 in the Laramie strata on both sides of the Rocky Moun- 

 tains. Thus the vertical range of some of these species 

 is no less than three thousand feet and their present 

 known geographical range more than a thousand miles. 



Besides the recognition of the unity of the widely dis- 

 tributed members of the formation of this great geological 

 period, bounded by those of undoubted cretaceous age 

 below, and those of equally undoubted tertiary age above ; 

 his further observations have left comparatively little 

 doubt that the "lake beds" of Dr. Hayden, as seen in 

 Middle Park, the " Brown's Park group " of Prof. Powell, 

 and the " Uinta group" of Mr. King, all belong to one 

 and the same epoch, later than, and distinctly separate 

 from, the Bridger groups. In that portion of the region 

 which lies adjacent to the southern base of the Uinta 

 mountain range, and which is traversed by Lake Fork 

 and the Du Chesne River, not only the Uinta group, but 

 both the Green River and Bridger groups also, are well 

 developed, each possessing all its peculiar and usual 

 characteristics, as seen at the typical localities in the 

 great Green River Basin, north of the Uinta Mountains. 

 This, added to the known existence of Bridger strata in 

 White River Valley, and the extensive area occupied by 

 the Green River group between White and Grand Rivers, 

 has added very largely to our knowledge of the south- 

 ward extension of those formations. 



In all the comparative examinations of the formations 

 or groups of strata that have just been indicated he has 

 paid special attention to their boundaries or planes of 

 demarcation, crossing and recrossing them wherever 

 opportunity offered, noting carefully every change of both 

 lithological and palaeontological characters. While he 

 has been able to recognise with satisfactory clearness the 

 three principal groups of cretaceous strata, namely, the 

 Dakota, Colorado, and Fox Hills, on both sides of the 

 Rocky and Uinta Mountains respectively, they evidently 

 constitute an unbroken series so far as their origin by 

 continuous sedimentation is concerned. While each of 

 the groups possesses its own peculiar palaeontological 

 characteristics, it is also true that certain species pass 

 beyond the recognised boundaries of each within the 

 series. 



The stratigraphical plane of demarcation between the 

 Fox Hills, the uppermost of the undoubted cretaceous 

 groups, and the Laramie group, the so-called post- creta- 

 ceous, is equally obscure ; but the two groups are pa'aeon- 



