44 THE JOURNAL OF GEOLOGY. 



relations, namely, that during the Miocene the country was a 

 series of plains and peneplains with low mountain ranges, or in 

 other words, the country was but little above its baselevel of 

 erosion. In no other position could such extensive plains have 

 been formed by erosion. 



GEOGRAPHY OF NORTHERN CALIFORNIA DURING THE MIOCENE. 



The lone formation being well stratified was evidently laid 

 down in a body of water having a distribution at least as 

 extensive as the formation itself. In the Sacramento valley, 

 as far north as Marysville Buttes, the water of the bay was 

 salt, as shown by the marine shells found at that point by Mr. 

 Lindgren.^ 



Upon the borders of this bay, at lone, where the conditions 

 were favorable for the accumulation of the vegetable matter to 

 form lignite, the water was regarded as fresh or brackish. Far- 

 ther northward only unios have been found, and the water in 

 which the lone formation originated was fresh. Beyond the 

 Lassen Peak region in northern California the water was undoubt- 

 edly fresh, but whether one large lake or a series of lakes, or a ' 

 water body connected directly with that of the Sacramento val- 

 ley as an estuary from the sea, is a matter of doubt. 



From the Great valley the sea swept across the region of the 

 Coast Range, perhaps near the latitude of Sacramento, and 

 extended northward over the area of the broad belt of sand- 

 stones upon the western slope to beyond Humboldt Bay. The 

 borders of the land must have been low and swampy to make 

 the conditions favorable for the accumulation and preservation 

 of vegetable matter to form coal. The Sierra Nevada and 

 Klamath Mountains themselves were lov/, with gentle slopes a3 

 compared with those of the present ranges, and the streams 

 flowed down their flanks in broad, shallow valleys instead of in 

 deep canons as they do now. 



^ Geologic Atlas of the United States, text accompanying the Sacramento sheet. 

 See also U. S. Geological Survey Bulletin,No. 84, by W. H. Dall and G. D. Harris, 

 p. 197. 



