604 THE JOURNAL OF GEOLOGY. 



found about 1,500 feet lower down, and not accompanied by any 

 of the species that were found above. 



The Triassic shales cover all the region near Silverthorn's 

 ferry on Pitt river, and most of the country north of Copper 

 City, on both sides of Squaw creek, and extend at least twenty 

 miles to the north, but the country is nearly inaccessible, and 

 almost no geological explorations have been made in it. 



The Cedar Formation. 



Distribution and character. — The Cedar formation was first 

 named by J. S. Diller 1 to include the Upper Triassic slates and 

 limestones of Indian valley, Plumas county, and Cedar creek, 

 Shasta county. It therefore includes the original Trias described 

 by Gabb 2 from "Gifford's ranch." 



In the Pitt river region the formation is very similar to that 

 in Plumas county, being composed of finely laminated shales 

 overlain by massive limestone, each rich in fossils. It seems to 

 overlie conformably the siliceous shales of the Pitt formation, 

 but the contact could not be observed. The Pitt shales usually 

 have a different dip and strike from the overlying limestones, 

 but the region is faulted and folded, and massive limestones do 

 not adapt themselves to contortions so readily as thin-bedded 

 shales. Certain recognizable horizons were always found at the 

 same distance below the limestone, and thus the conformity 

 becomes probable. 



The formation is first seen at Cedar creek, south of Pitt river, 

 from which locality the formation was named. It has also been 

 cited by J. S. Diller 3 from near Texas Springs, southwest of 

 Redding. But the formation is best studied from Brock's ranch 

 on Pitt river, northward across Squaw creek, and nearly to the 

 McCloud river, a distance of over twenty-five miles. It is com- 

 posed of the Swearinger slates, overlain conformably by the 



'Geological Atlas U. S. Geol. Survey, Lasson Peak Sheet, 1892, Descriptive text. 



2 Paleontology of California, Vol. I. 



3 Bull Geol. Soc. Am. Vol. IV., p. 221. 



