THE FRESHWATER TERTIARY FORMATIONS 

 OF THE ROCKY MOUNTAIN REGION. 



By W. M. Davis. 



Received January 29, 1900. Presented February 14, 1900. 



CONTENTS. 



1. Piedmont Depositories of Moun- 



tain Waste 345 



2. The Various Origins of Stratified 



Deposits :;i7 



3. Accounts of Tertiary Lakes in 



tlie Rocky Mountain Region . I'.IT 



4. Characteristics of Lake Deposits 351 



5. The Vermillion Creek Beds of 



Wyoming 354 



6. The Arapahoe and Denver For- 



mations of Colorado .... 356 



7. Lacustrine and Fluviatilc Quater- 



nary Deposits 359 



8. Continental Deposits .... 360 



9. Fluviatile Deposits .... 360 



10. The Indo-Gangetic Fluviatile 



Plain 362 



11. Fluviatile Deposits of the Great 



Plains 363 



12. Fluviatile Basin Deposits . . 364 



13. Pocky Mountain Basin De- 



posits 365 



14. Deposits in Arid Basins . . . 366 



15. vEolian Deposits 369 



16. Summary 370 



1. Piedmont Depositories of Mountain Waste. — Extensive plains 

 stretch forward from the base of many mountain ranges. They are 

 formed of the waste brought from the valleys in the mountains by the 

 streams that have for ages drained them. Sometimes the plains are 

 open and slope gently to the seashore, as in northern India and northern 

 Italy ; sometimes they occupy a basin drained through a gap in one of 

 its enclosing ranges, as in Hungary and California ; sometimes they fill 

 the floors of interior continental basins from which no river escapes to 

 the sea, as in Utah and Nevada, Persia and Central Asia. Although 

 Piedmont fluviatile plains are familiar geographical features, their genetic 

 association with mountains is seldom stated explicitly. It is seldom that 

 sufficient importance is given to the complimentary relation in which the 

 plains stand to the mountain valleys whence their materials have been 

 derived, even though some emphasis may be allowed to the fact that the 



