192 GEOLOGICAL SURVEY OF THE TERRITORIES. 



die tertiary beds by iiplieaval at Bear River City, Evanston, and Coal- 

 ville, the Bear River group. 



In the valley of Weber Eiver, from Morgan City to Devil's Gate, 

 there is a thickness of one thousand to twelve hundred feet of sands, 

 sandstones, and marls, of a light color for the most part, which I regard 

 as of upper tertiary age. These newer beds must have not only occu- 

 pied this expansion of the Weber Valley, but also all of Salt Lake Val- 

 ley, for remnants of it are seen all along the margins of the mountains 

 inclosing Salt Lake Valley. I have obtained one species of helix near 

 Salt Lake City from this group, which very much resembles a species 

 obtained from the Wind River deposits, near the source of Wind River. 

 I found this series of beds so widely extended and so largely developed 

 in Weber Valley aud Salt Lake Valley, that I regard it as worthy of a 

 distinct name, and in consequence have called it the Salt Lake gToup. 



Some years ago, in a paper i)ublished in the proceedings of the Acad- 

 emy of Natural Sciences, at Philadelphia, Mr. Meek and the writer pro- 

 posed names for certain groujis of tertiary strata, which might be added 

 to the list already given : 



First. The Fort Union or great lignite group, which occupies the whole 

 country around Fort Union near the mouth of the Yellowstone, extend- 

 ing north into the British possessions to nnknown distances, also south- 

 ward on the Missouri River to Fort Clark. It also extends along the 

 eastern flanks of the mountains, probably to Denver, Colorado, and 

 perhaps further. 



Second. The Wind River deposits are limited, so far as we now know, 

 to the Wind River Valley. The sediments are composed of indurated 

 sands and clays, with a few layers of sandstones and some calcareous 

 concretions; and the prevailing color is very light gray, sometimes 

 brown with reddish bands. The fossils thus far found are fragments of 

 *Trionyx, Testudo, Helix, Vivijpara, petrified wood, &c., doubtless of middle 

 tertiary age. 



Third. The White River group, best shown on White River, Dakota, 

 but covering a very extended area — at least one hundred and fifty 

 thousand square miles. The sediments are composed of white and light 

 drp^b indnrated sands, clays, and marls, with some beds of sandstones 

 and limestones 5 is purely fresh water, and remarkable as one of the 

 most wonderful deposits of extinct mammalia on the globe — middle 

 tertiary. 



Fourth. The Loup River beds, which certainly form a most sin- 

 gular and remarkable group. They are composed for the most part of 

 fine, loose gray or brown sands, with some layers of limestone contain- 

 ing a distinct and most remarkable fiiuna, composed of wolves, foxes, 

 tigers, hyenas, camels, horses, mastodons, elephants, &c. There are also 

 numerous fresh-water andland shells^ perhaps of recent species, npper ter- 

 tiary. To these groups might be added the Judith River beds, a small basin 

 on the Missouri River, near the foot of the mountains, about fifteen to 

 twenty miles in width aud forty miles in length. This group is probably 

 of lower tertiary age, but I think it was always separated from the great 

 lignite group. In my final report I hope to be able to illustrate each one 

 of these groups by "the organic remains peculiar to it, and, if possible, 

 show the relations of each one to the other and to all. Further explo- 

 rations of. the Territories will reveal many more of these lake basins, for 

 I am now convinced that all over the great area west of the Mississippi 

 to the Pacific coast the evidence of the existence of these lakes will be 

 more or less clear. 



