56 



GEOLOGICAL SURVEY OF THE TEERITOEIES. 



General section of tlie Tertiary roclcs of NebrasTca. 



The details of all these formations will be discussed more fully in the 

 final report. 



Commencing with the oldest of these Tertiary basins, we have — 



1st. Judith Eiver basin, which is located near the entrance of the 

 Judith into the Missouri, and is separated by the latter river into two 

 nearly equal portions. It covers an area of about fifteen to twenty miles 

 east and west, and forty miles from north to south. 



This basin is one of much interest, as it marks the dawn of the Ter- 

 tiary period in the West, by means of the transition from brackish to 

 strictly fresh water types. It is also remarkable for containing the 

 remains of some curious reptiles and animals, reminding the paleon- 

 tologist of those of the Wealden of England. 



2d. The great lignite basin which occupies all the country from Heart 

 Eiver to the Muscle-Shell — most of the Valley of the Yellowstone — 

 extends for an unknown distance northward into the British possessions 

 and southward at least to the North Platte,where the beds of the fourth 

 basin overlap, coming to the surface again at Pike's Peak, and extend- 

 ing to Eaton Pass, in New Mexico. 



The limits of this great basin have not yet been determined. Although 

 not known to occur within the present defined limits of the State of 

 Nebraska, it will undoubtedly have an influence on the prosperity of 

 the State, on account of the extensive lignite beds which occur in it. 

 Along the Missouri and Yellowstone Elvers are forty or fifty beds of 



