State Agricultural Society. 129 



THE 1"00T-1IIIJ.S OF THI- SIHKKA. 



RKAI) BEFORE THE CALIFORNIA ACADEMY OF SCIENCE JANUARY FIFTH, 

 EIGHTEEN HUNDRED AND SEVENTY-NINE— BY B. B. REDDING. 



GEOLOGICAL FORMATION. 



The western base of the Sierra Nevada bordering the Sacramento 

 Valley is known in this State as the foot-hill re<;ion. These foot- 

 hills extend from Redding, at the northern end of the valley, to 

 Caliente, at the southern extremity, a distance of three hundred and 

 fifty jiiiles. I am indebted to Mr. A. Bowman, formerly of the State 

 Geological Survey, for the following description of the formation of 

 this i)ortion of the State. He says: "Generally speaking, there are 

 gradually rising low outliers of upper tertiary gravels, sands, and 

 clays all along the western base of the Sierra. They are often capped 

 by volcanic matter, and cut through by erosions — the dry, winding 

 arroyos through the fiattish hills that are familiar to every one who 

 has followed along the edge of the Sacramento and San Joaquin 

 plains. These erosions in some places cut down into the middle ter- 

 tiary, and even into the cretaceous beds; but there is little surface 

 area of the latter. On the plains all is covered up by the recent 

 deposits. Patches occur of middle tertiary and upper tertiary, where 

 denudation has removed great masses of tertiary country, with these 

 exceptions: for example, at Millerton, on both sides of the San Joa- 

 quin, a i)atch of middle tertiary hills about three by ten miles is 

 seen, and at lone Valley, several miles S(iuar^ of steep hills of this 

 period are laid down in slightly pitching beds. The tertiary forma- 

 tions reach away up into the Sierra, in the shape of ancient river 

 deposits. They change at from three hundred to one thousand five 

 hundred feet altitude into fiuviatile deposits; although a large por- 

 tion of the plains, tertiary to below the present sea level, is also 

 fiuviatile, interbcdded with lacustrine or marine, sometimes appa- 

 rently in alternate order. The surface areas may be .'^aid to change, 

 going eastward, from recent to upi)er tertiary (pliocene) as the soil 

 belongs above or below the volcanic outflow; and then to the slate 

 and granite formations of the Sierra, extending to the summit. The 

 cretaceous formation shows scarcely any surface area along the base 

 of the Sierra except in Shasta County, although from Folsom north 

 the ravines and canons expose its edges — especially north of Oroville. 

 At Reading's ranch, and from there north to Fit River, the flat coun- 

 try is all cretaceous, the tertiary being mostly removed by denuda- 

 tion. The same is true of patches between there and Oroville. The 

 patc-h between Fort Reading and Fit Fiver is abc>ut twenty miles 

 square. The foot-hill cretaceous of Butte and Shasta Counties is 

 overlaid by the Shasta coal measures which are, I think, middle or 

 upper tertiary; and these again by the u{)per tertiary formation of 

 the ancient river gravel period, and by the volcanic outflows from 

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