8 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



inaugurated. An unconformity was also established by 

 paleontological evidence, and the confusion that existed in 

 regard to the various species of Aucella was finally settled. 



Paralleling in the Coast Ranges this separation of the 

 Mariposa formation from the Cretaceous, the rocks that 

 were thought to belong to the Shasta Group have been 

 shown to consist of two unconformable series. It is due 

 largely to the work of H. W. Fairbanks (1892, 1893, 1895, 

 1896), Diller and Stanton (1894) and J. S. Diller(i893) that 

 certain metamorphic and semi-metamorphic rocks of the 

 Coast Ranges and the Klamath Mountains are recognized 

 as lying unconformably below the Aticella-hQ^irmg shales, 

 which have been called Knoxville. 



The Cretaceous series has been found to contain few, if 

 any, rocks that have suffered a high degree of metamor- 

 phism. The older complex is composed of both igneous 

 and stratified rocks that may eventually prove to include 

 members of Paleozoic, as well as of Mesozoic age, embrac- 

 ing the Santa Lucia series of Willis (1900) and at least a 

 portion of the Franciscan (Lawson, 1895), or Golden 

 Gate (Fairbanks, 1895) series. The latter series was 

 named from its important development in the vicinity of 

 San Francisco Bay; it extends southward from the Klam- 

 ath Mountains along- the coast of California, and in the 

 Coast Ranges forms the basement of many later deposits. 

 The Franciscan series is generally believed to be in part 

 Cretaceous ; but much of it, including the Radiolarian 

 cherts and some of the limestones and slates, is known to 

 antedate the Cretaceous. 



In the paper by Diller and Stanton (1894), referred 

 to above, it is shown that in the upper Sacramento Valley, 

 on the flanks of the Klamath Mountains, beds that have 

 been called Knoxville overlie unconformably an older 

 metamorphic series, partly sedimentary, and partly igneous 

 and cr3'stalline. The Cretaceous series was carefully 

 studied in two more or less complete sections on the 

 western side of the Sacramento Valley, ranging eastward 

 from the Yallo Bally and Bally Choop mountains. The 



