542 O. E. MEINZER LAKES OF THE BASIN-AND-RANGE PROVINCE 



posures to afford important results in Tertiary and Quaternary stratig- 

 raphy, structure, and paleontology. I have spent a good many summers 

 in these basin valleys, studying their water resources, and I am deeply 

 impressed with the opportunity they present for further geologic work. 



The early geologists were struck by the contrast between these basin 

 valleys and the valleys in humid regions, and they did some memorable 

 work in the valley areas which resulted in such classic papers as the 

 Bonneville and Lahontan monographs. Later geologists working in the 

 region, however, largely ignored the valleys or gave them only superficial 

 attention. In recent years interest has been revived in these valleys 

 through two lines of economic geology — the study of the ground-water 

 resources of the desert region and the search for potash. 



The main purpose of the present paper is to present a nearly complete 

 map of the Pleistocene lakes of the Basin-and-Range Province which has 

 resulted from this recent work. In addition, I will discuss briefly the 

 relation of ground-water discharge by evaporation and transpiration in 

 this province to the discharge from surface lakes, as developed by our 

 recent water-resource investigations, and will call attention to studies of 

 Pleistocene climate which I hope can be made in the future by comparing 

 the Pleistocene with the present hydrology of the province. 



Pleistocene Lakes 



The map of Pleistocene lakes presented herewith (figure 1) shows 68 

 ancient lakes, including the two giant lakes — Bonneville and Lahontan. 

 A few Pleistocene lake beds* probably still remain undiscovered, but for 

 most of the region the map is complete. The ancient lakes were mapped 

 chiefly by their shore features, many of which are still very conspicuous 

 and distinct. In addition to the closed basins that held these lakes witb 

 definite shorelines, there are doubtless others that contained small 

 ephemeral lakes which left no distinct shore features. 



Somewhat more than half of these lakes were mapped by Russell and 

 Gilbert many years ago, but about 25 have been mapped (and, for the 

 most part, discovered) in recent years in connection with the ground- 

 water and potash investigations of the U. S. Geological Survey. It should 

 be noted that the newly mapped lakes are distributed over a large region 

 which had previously been almost unexplored for these features, and that 

 they represent a wide range in latitude, altitude, and climate. They are, 

 therefore, especially significant in the interpretation of the hydrology and 

 climate of the epoch in which they existed. The lakes mapped by Russell 

 and Gilbert were found in northern and middle Nevada and adjacent 



