GEOLOGICAL SURVEY OF THE TERRITORIES. 



93 



to the surface very often, not unfrequently in 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 period 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 tlw tertiary rocks of Nebraska. 



Names. 



Subdivisions. 



Localities. 





! >-8 



II 



Loup Eiver 

 beds. 



White Riv- 

 er Group. 



Wind Eiver 

 deposits. 



Fort "Union 

 or Great 

 Lignite 

 Group. 



Fine loose sand, with some layers of lime- 

 stone; contains bones of Canis, Felis, Cas- 

 tor, Equus, Mastodon, Testudo, <£c, some 

 of which are scarcely distinguishable 

 from living species. Also Helix, Physa, 

 Succinea, probably of recent species. 

 All fresh-water and land types. 



White and light-drab clays, with some 

 beds of sandstone and local layers of 

 limestone. Fossils : Oreodon, Tiianothe- 

 Hum, Ghosropotamus, Rhinoceros, Anchi- 

 therium, Hycenodon, Machairodus, Tri- 

 onyx, Testudo, Helix, Planorbis, Limnoza, 

 petrified wood, &c. All extinct. No 

 brackish-water or marine remains. 



Light-gray and ash-colored sandstones, 

 with more or less argillaceous layers. 

 Fossils : fragments of Trionyx, Testudo, 

 with large Helix, Vivipara, petrified 

 wood, &c. No marine or brackish- water 

 types. 



Beds of clay and sand, with round ferru- 

 ginous concretions, and numerous beds, 

 seams, and local deposits of lignite, great 

 numbers of dycotyledonous leaves, 

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

 TTlmus, Populus, die, with very large 

 leaves of true fan palms. Also Helix, 

 Ifelania, Yivipam, Corbicula, Unio, Os- 

 trea, Corbida, and scales of Lepido- 

 tus, with bones of Trionyx, Emys, Comp- 

 semys, Crocodilus, <6e. 



Feet. 

 300 to 400 



1,000 

 or more. 



1,500 



to 

 3,000 



2,000 

 or more. 



On Loup fork of Platte Eiver 

 extending north to Niobran 

 Eiver, and south to an ud 

 known distance beyond tht 

 Platte. 



Bad Lands of White Eiver 

 under the Loup Eiver beds, 

 on Niobrara, and across thu 

 country to the Platte. 



Wind Eiver Valley ; also west 

 of Wind Eiver Mountains. 



Occupies the whole country 

 around Fort Union, extend- 

 ing north into the British 

 possessions to unknown dis- 

 tances; also southward to 

 Fort Clark. Seen under the 

 WhiteEiver Group on North 

 Platte Eiver above Fort 

 Laramie. Also on west side 

 of Wind Eiver Mountains. 



< to 



