GEOLOGY OF THE MISSOURI VALLEY. 



CHAPTEE VII. 



GENERAL VIEW OF THE GEOLOGY OF THE MISSOURI VALLEY. 



Iii order that our description of the geology of that belt of country 

 bordering the line of the Union Pacific Eailroad may be more clearly 

 understood, we may in this chapter take a somewhat hasty glance at the 

 principal geological features of the vast area drained by the Missouri 

 Eiver and its tributaries. The geologist is dependent for his knowledge 

 of the earth's crust, either on natural sections formed by the channels 

 of rivers, or the upheavals of mountain chains, or on the artificial cuts 

 along railways, or artesian borings. The great Missouri cuts a section 

 from its source in the mountains to the Mississippi, a distance of nearly 

 3,000 miles, affording an excellent opportunity for studying the various 

 geological formations which occur in the Northwest. The branches also, 

 which make their way from distant points on either side of the Missouri, 

 cut the country up in every direction, so that it is hardly possible to fail 

 in obtaining at least, an approximately correct interpretation of the 

 records. The cuts along the line of the railroad are, as it were, slices 

 in the earth's crust which often reveal the nature of the underlying 

 formations with wonderful clearness, throwing a flood of light upon ob- 

 scure points. Many of the observations also, which were made for prac- 

 tical purposes by the engineers, as well as the exploration for useful 

 minerals in the vicinity of the road, may be brought into the service of 

 science. Thus the elevations which have been taken with great care 

 across the continent from Omaha to San Francisco are very useful. 

 Along a well-known line of travel, the attention of the student of 

 geology will most likely be attracted toward the principal geological 

 features, and on this account I hope to make the succeeding chapters a 

 sort of guide in this respect. My observations, which have extended 

 over a period of about three years, may be regarded as correct in the main, 

 though every year new facts will be added. 



Before starting on our westward tour let us study for a little time the 

 wonderful section which is revealed to us along the channel of the Mis- 

 souri Eiver. It has long been known that the northeastern portion of 

 Nebraska is underlaid by rocks of the upper coal measures. These 

 rocks are well shown from the south line of the State to the mouth of 

 the Platte Eiver, where they are partially concealed by a great thick- 

 ness of recent deposits. They gradually disappear beneath the water- 

 level near De Soto, about thirty miles aboveOmaha. If we ascend the 

 Platte River for a short distance we shall find the carboniferous lime- 

 stones finely exposed, and the opportunities for their study are very 

 much aided by the numerous quarries which have been opened. They, 

 in their turn, pass beneath the water-level of the river, near the mouth 

 of the Elkhorn, and are not again visible until they are exposed along 

 flanks of the mountain ranges. So far as Nebraska is concerned r the 

 carboniferous rocks seem to be directly overlaid by the rusty sandstones 

 of the lower cretaceous, No. 1. In the valley of the Big and Little Blue 



