METAMORPHIC SERIES OF SHASTA COUNTY. 6oi 



seems to be characteristic of Upper Carboniferous, in Nevada is 

 found also in Lower Carboniferous. But the most decisive proof 

 of the Upper Carboniferous age of these strata is their position 

 so far above the Baird shales, which have been shown in this 

 paper to be equivalent to the Lower Carboniferous of the Eureka 

 district, Nevada, which is known to occur 3,000 feet above the 

 base of the formation. 



The McCloud limestone is probably equivalent to the lime- 

 stone of the Caribou 1 formation of Plumas county. But J. S. 

 Diller 2 thinks that they belong to a lower horizon than that 

 assigned them by the writer. The Robinson 3 beds of the Tay- 

 lorville section are probably higher up in the section, but never- 

 theless the McCloud limestone is, in part at least, equivalent to 

 the Coal Measures. 



The Pitt Formation.' 1 



General character of the rocks. The Pitt formation overlies 

 conformably the McCloud limestone, and consists roughly esti- 

 mated of about 3,000 feet of siliceous and calcareous shales, con- 

 glomerates and tuffs. The rocks in most places are highly meta- 

 morphosed, very poor in fossils, and folded to such a degree 

 that the stratigraphy is obscure. The general strike is north 

 and south, and the dip generally toward the east, since most of 

 the folds are overthrown. 



The formation is largely developed in the region near the 

 junction of the Pitt and the McCloud rivers. It contains both 

 Carboniferous and Triassic rocks, in an apparently conformable 

 series, both with a decisive fauna, the presence of Upper Carbon- 

 iferous and Middle Trias being proved by fossils. 



The Carbo?iiferous argillites. The oldest fossiliferous strata 

 of the Pitt formation are of Upper Carboniferous age, and are 

 found on the east bank of the McCloud river, about nine miles 



1 U. S. Geol. Survey, Geological Atlas, Lassen Peak Sheet, 1892, J. S. Diller. 



2 Bull. Geol. Soc. Am., Vol. III., p. 375. 



'•Bull. Geol. Soc. Am., Vol. V., p. 247. 



■♦H. W. Fairbanks, Ms. 



