GEOLOGICAL SURVEY OF THE TERRITORIES. 



93 



to tlie surface very often, not unfrequently iu unexpected localities, as 

 is observed on the Yellowstone, where the fossiliferous beds of No. 4 are 

 exposed in the channel of the stream for a distance of sixty miles. 

 Nowhere south of the Missouri Eiver have I seen any locality where a 

 distinct line of separation could be drawn between the upper and lower 

 series, and it is probable that this line will be best shown on the Upper 

 Missouri of any portion of the West. The break here is quite plain, 

 lithologically, and so far as the organic remains are concerned, our ex- 

 plorations have not yet been able to secure a single species that passes 

 from one to the other. The next important feature in the geology of 

 the West are the great lake basins, which seem to set in the older forma- 

 tions and in each other like dishes, and these are most properly called 

 basins. The principal one is the Fort Union, or Great Lignite Group, 

 which forms the transition group from the strictly marine condition of the 

 cretaceous j)eriod to the epoch of the numerous fresh- water lakes which 

 were scattered all over the country west of the Mississippi. Now that 

 the attention of explorers has been called to this remarkable system of 

 lakes, I have no doubt they will be found to have existed all over the 

 western portion of the continent, from the extreme north to the far 

 south. In the chapter by Dr. Newberry on the ancient lakes of the 

 West there is a most graphic description, to which the reader is referred. 

 The following general section conveys a clear idea of the different groups, 

 so far as they were known, up to the time of its first publication in the 

 proceedings of the Academy of Natural Sciences, December, 1801. As 

 these groups will be frequently referred to in this report as well as suc- 

 ceeding reports, and as each year's explorations extends their area or 

 adds new facts to our knowledge of them, it will be a matter of interest. 



General section of the tertiary ro4cs of Nebraska. 











03 



Names. 



Subdivisions. 



a 

 o 



2 



H 



Localities. 









Feet. 







Loup Eiver 



Fine loose sand, with some layers of lime- 



300 to 400 



On Loup fork of Platte River, 



) 



beds. 



stone; contains bones of Cam's, Felis, Cas- 





extending north to Niobrara 



<s 





tor, Equus, Mastodon, Testudo, &c, some 





River, and south to an un- 



1 a 





of "which are scarcely distinguishable 





known distance beyond the 



■ o 





from living species. Also Helix, Physa, 





Platte. 



•rt 





Succinea, probably of recent species. 







Ph 





All fresh-water and land types. 









White Riv- 



White and light-drab clays, with some 



1,000 



Bad Lands of White River, 



1 



er Group. 



beds of sandstone and local layers of 



or more. 



under tho Loup River beds, 







limestone. Fossils : Oreodon, Tiianothe- 





on Niobrara, and across the 



6 





Hum, Ghceropotamus, Rhinoceros, Anchi- 





country to the Platte. 



o 





therium, Hycenodon, Machairodus, Tri- 







' o 





onyx, Testudo, Helix, Planorbis, Idmnoea, 







§ 





petrified wood, &c. All extinct. No 











brackish- water or marine remains. 









Wind River 



Light-gray and ash-colored sandstones, 



1,500 



Wind River Valley ; also west 





deposits. 



with more or less argillaceous layers. 



to 



of Wind River Mountains. 







Fossils : fragments of Trionyx, Testudo, 



2,000 





>? 





with large Helix, Vivipara, petrified 











wood, &c. No marine or brackish- water 

 types. 

 Beds of clay and sand, with round ferru- 









Fort Union 



2,000 



Occupies the whole country 





or Great 



ginous concretions, and numerous beds, 



or more. 



around Fort Union, extend- 





Lignite 



seams, and local deposits of lignite, great 





ing north into the British 



^ 



Group. 



numbers of dycotyledonous leaves, 





possessions to unknown dis- 



^_ 





stems, &c, of the genera Platanus, Acer, 





tances; also southward to 



o 





TTlrnus, Populus, &c, with very large 





Fort Clark. Seen under the 



*- a 





leaves of true fan palms. Also Helix, 





WhiteRiver Group on North 



o 





Melania, Vivipara, Gorbicula, TJnio, Os- 





Platte River above Fort 



W 





trea, Corbula, and scales of Lepido- 





Laramie. Also on west side 







tus, with bones of Trionyx, Emys, Comp- 





of Wind River Mountains. 







semys, Crocodilus, &c. 









