118 University of California Publications in Geological Sciences 



hills. Precipitation was distributed chiefly in winter, though summer showers were 

 present in minor amount. Summers were warm to hot, with the average July maxi- 

 mum approximately 85° F. The average January temperature was approximately 

 45° F., which is about 15° F. higher than that now in the area. Extreme winter 

 temperatures apparently did not fall much below 10° F., as compared with -19° F. 

 today. The growing season probably was not less than 200 to 230 days, whereas it 

 is now 145 days. 



AGE 



Stratigraphic Evidence 



The sediments in the Verdi area were originally considered to be of Miocene age. 

 This assignment was based on the age implication of a fragmentary rhinoceros 

 tooth and a small fresh-water molluscan fauna recovered from the basal-type 

 Truckee formation at Fossil Hill in the northeastern Hot Springs (Kawsoh) 

 Mountains 60 miles northeast of Verdi (King, 1878, vol. 1, pp. 423^24). Since 

 the sediments in the Verdi area were tilted to about the same degree as the Truckee, 

 it was concluded that they were of approximately the same age (King, 1878, vol. 2, 

 p. 849) . Although the Verdi sediments appear on the Atlas of the Fortieth Parallel 

 Survey as Truckee, King (1878, vol. 2, p. 849) clearly realized that the Verdi sec- 

 tion differed lithologically from the type Truckee. 



Mammalian faunas having greater age value than the rhinoceros tooth have 

 been discovered more recently at two localities in the lower part of the Truckee 

 formation. The small Hazen fauna appears to be Late Clarendonian to Early 

 Hemphillian (Stirton, 1939, p. 635). The larger Nightingale Road fauna contains 

 a number of types distinctive of the Late Clarendonian (MacDonald, 1950 ; 1956) . 

 A recent revision of the molluscan fauna, as based on new collections from the 

 original locality in the basal type Truckee section, indicates that it is Pliocene 

 (Yen, 1950). Since the Verdi flora occurs in the Coal Valley formation, which is 

 now known to interfinger with the Truckee in the Carson Sink area (Axelrod, 

 1956, p. 141), it must also be Pliocene. This age assignment for the Verdi flora, 

 as based on its stratigraphic relations, is supported fully by the paleontological 

 evidence now available in the Verdi basin. 



Paleontologic Evidence 



plants 



The first fossil plants from the Verdi basin to be evaluated in terms of age were 

 those represented in the small collection that was secured by Anderson. J. P. Smith 

 (in Anderson, 1909, p. 483) identified species of pine, birch, willow, serviceberry, 

 and manzanita in the collection and suggested that it was Miocene ; it is worth not- 

 ing here that Smith's identifications appear to have been far more realistic than 

 those made by Knowlton (see below). Unfortunately, the fossils were neither fig- 

 ured nor referred to fossil species, and although Anderson states that the collection 

 was deposited at Stanford University, it could not be located there. It is to be 

 hoped that this collection can be found, for if birch and serviceberry are repre- 

 sented in it, they will add materially to this small flora. 



