MESOZOIC TIME — TRIASSIC AND JURASSIC. 809 



there took place after the Triassic. In the Sierra Nevada an unconformity 

 occurs, according to Diller, between the Lias and Upper Trias of the Taylor- 

 ville region, but the succession of deposits shows that no emergence in that 

 portion of the Sierra Nevada accompanied the disturbance. In the Island 

 belt of British Columbia, along Vancouver and the Queen Charlotte Islands, an 

 emergence occurred after the Triassic period; for no Jurassic beds exist 

 between the Triassic formation of the region and the Cretaceous ; moreover, 

 at some time between the Triassic period and the Cretaceous, according to 

 Gr. M. Dawson, an extensive upturning of the Triassic beds took place; but 

 whether at the close of the Triassic or of the Jurassic is left uncertain 

 (1886, 1887). 



The close of the Jurassic period was the time of the making of the Sierra 

 Nevada Range, as announced by J. D. Whitney in 1864 (Am. Jour. Sc, 

 xxxviii., 1864 ; Eep. GeoL, 1865), after the discovery of Triassic and Jurassic 

 fossils in Plumas County, and of Jurassic in the Auriferous slates of Mariposa 

 County and other regions. This conclusion has been questioned and the 

 event referred to the Middle Cretaceous, on the ground chiefly of resemblance 

 between the Aucellae of the Jurassic Sierra slates and those of the Lower 

 Cretaceous ; but it has been fully confirmed by the study of the Mariposa 

 and other fossils by Hyatt and others, and by the fact of the unconform- 

 ability of the Lower Cretaceous with the rocks of the Sierra in many places 

 west of the Sacramento River. 



It is also sustained by the fact of the conformability of the Lower and 

 Upper Cretaceous, or the Shasta and Chico series, as observed by Diller; 

 who has, moreover, traced the wuconformability, not only along the west side 

 of the Sacramento, from Pit River southward by Redding, Horsetown, and 

 Ono, into Tehama County, but also northward by Yreka and Ashland, far 

 into Oregon. Moreover, other ranges to the west and north participated in 

 the upturning; for the Coast Range and the Klamath Mountains were 

 parts of the result, according to Diller and Fairbanks ; and it may be that 

 still others in the Sierra line, to the north or south, were then formed. 



The black slates and siliceous rocks of the auriferous belt of the Sierra 

 are associated with hydromica schist, hornblende schist, serpentine, crystal- 

 line limestone, along with some sandstone, and with limestone which is 

 semi-crystalline. Prom the Mariposa region northward they commonly have 

 a dip eastward of 60° to 80° or 90°. The relative positions of the rocks of 

 the belt are finely exhibited on the colored geological maps of parts of the 

 Sierra region published by the United States Geological Survey, prepared 

 chiefly by Lindgren and Turner. They show by colors the positions of the 

 areas of outcrop of the granite or dioryte, which makes the core of the Sierra, 

 and also of the various eruptive rocks of the region as well as the belts which 

 make up the Auriferous series. 



In the Taylorville region, Plumas County, the beds, ranging from Upper 

 Jurassic to the Silurian, are partly in overthrust flexures, the thrust being 

 to the eastward (landward) as described and figured by Diller (G. Soc. Avi., 



