GEOLOGICAL EEPOET. 



INTRODUCTION. 



In order that the relation of the different geological formations re- 

 ferred to in this report may be more clearly understood, I have thought 

 it best to commence with the upper coal measures as exposed along the 

 Missouri River near Omaha and the mouth of the Platte. 



Omaha, which is well known to be the eastern terminus of the Union 

 Pacific railroad, is built upon the northwestern rim of the coal meas- 

 ures as seen along the Lower Missouri. These rocks occupy a consid- 

 erable portion of the State south of the Platte River, but north of tbat 

 point they cover only a small portion of Sarpy and Douglas Counties. 

 The last exposure of any importance is near the point decided upon as 

 the location for the railroad bridge across the Missouri. The limestones 

 at this point have been quarried for many years, but the amount of 

 labor required to remove the vast thickness of marl and drift above it,, 

 will diminish greatly the importance of this quarry. Near Florence 

 these limestones are seen in the bottom of the river at very low water, 

 and near De Soto, obscure exposures have been detected. From that 

 point to the foot of the mountains these rocks are not again seen. Along 

 the Platte River for about eight miles there are extensive quarries of 

 limestone that are very useful for building purposes. Scattered over 

 the surface of the country in the two couuties of Douglas and SarjDy, are 

 exposures of the rusty sandstone of the Dakota group 5 and at the moutk 

 of the Elkhorn River all traces of the coal measure rocks have disap- 

 peared, and do not reappear again until we reach the very margin of 

 the mountains, over five hundred miles to the westward. After leaving 

 the mouth of the Elkhorn very few exposures of rocks are seen for the 

 next hundred miles, but there are enough to show that the underlying: 

 rocks are of cretaceous age. Near the mouth of Elkhorn River the 

 sandstones of the Dakota group are seen, while on the distant hills- 

 traces of the yellow, chalky limestone. No. 3, occur. After reaching a 

 point along the Platte about one hundred miles west of Omaha, the light, 

 yellowish marls and sands of the White River grouj) overlap the older 

 rocks and occupy the country to the very margins of the Rocky Mountains. 

 But the most important formation, and one that has a more favorable 

 influence on the State of Nebraska than any other, is of very recent date 

 in geological history. In the valley of the Missouri River, extending 

 up nearly to Fort Pierre, and also to the mouth of the Missouri, and 

 probably southward to the valley of Mexico, is a deposit of yellow marl 

 varying in thickness from a few feet to several hundred. It has been called 

 " the bluff formation," for it constitutes the picturesque bluffs or high hills 

 which form the most conspicuous features in the scenery along the Mis- 

 souri River. This yellow marl also enters largely into the composition 

 of the soil of the vast bottom lands of the river which are so justly cel- 

 ebrated for their fertility. It is, however, in the immediate proximity 

 to the water-courses that this yellow marl deposit is the thickest, and it 

 gradually diminishes in depth as we recede from themj still, it is to this 



