GEOLOGICAL SURVEY OF THE' TERRITORIES. 



CHAPTER I. 

 INTEODUCTOEY. 



I had intended in this report to present a careful resume of the geol- 

 ogy of the jS^orthwest, so far as my explorations have extended ; but the 

 unusual pressure of executive duties, in connection with so large a party, 

 has prevented me. I shall, thereforej in this chapter pass hastily in 

 review some of the more imj)ortant points that occur along our route, 

 from Cheyenne to the Yellowstone region. 



I vdll first notice briefly the lignitic formations as they appear along 

 our route. Inasmuch as there has been some diversity of opinion among 

 geologists in regard to the precis*e position in the geological scale of the 

 great coal or lignitic group of the West, I desired to secure all the evi- 

 dence possible bearing on that point. For this purpose Professor Leo 

 Lesquereux, our great authority on fossil botany, was directed to spend 

 a few months in exploring the coal-beds of the West. He passed along 

 the Kansas Pacific Eailway to Denver, Colorado, examining the Creta- 

 ceous coal-beds on the route. From Denver he proceeded along the 

 base of the mountains to Santa Fe, and returning, made a careful study 

 of the coal-groups as shown in the vicinity of Denver. He then visited 

 the principal points of interest along the Union Pacific Eailroad to Salt 

 Lake City. The reader is referred to his valuable reports in this vol- 

 ume for the results of his examinations. 



Besides the lignitic group, there is a series of extensive lake-basins 

 in the interior of our continent which have already yielded an astonish- 

 ing number of remarkable vertebrate remains. Inasmuch as greater 

 weight is attached by some geologists to the testimony of the higher 

 order of organic remains. Professor Joseph Leidy and Professor E. D. 

 Cope, both of whom are justly regarded as the most eminent comi)ara- 

 tive anatomists of our country, made a careful exploration of the lignitic 

 and more modern lake groups, under the auspices of the survey. Their 

 reports, appended to this volume, will throw great light on the age of 

 these formations. 



Mr. F. B. Meek, paleontologist of , the survey, assisted by Mr. H. M. 

 Bannister, made a careful study of the lignitic group from the inverte- 

 brate side, and their reports contain most valuable results. The time 

 has been so short for the preparation of this re]3ort that I have not been 

 able to examine the results of the studies of these eminent gentlemen, 

 and therefore cannot present their conclusions in regard to the age of 

 these deposits with certainty. I am of the impression, however, that 

 Professor Lesquereux concludes, from his study of the fossil plants, that 

 the lignitic strata are mostly Eocene. Mr. Meek believes them to be 

 upper Cretaceous, passing up through a series of transition beds to 

 Eocene; while Professor Cope regards them as of Cretaceous age. 

 All these gentlemen must be regarded as individually responsible for 

 the opinions expressed in their reports. 



