244 J. p. SMITH — AGE OF THE AURIFEROUS SLATES. 



The Auriferous slates have long been a puzzle to California geologists, 

 and, on account of the scientific as Avell as economic interest attached to 

 them, much has been written — hardly any two writers agreeing — about 

 their age. 



This paper is intended to present the facts known at the present time. 



Opinions of previous Writers. 



1858. The first geologist to write about the age of the Auriferous slates 

 of the Sierra Nevada was W. P. Blake,^ who stated that a great part of 

 the gold-bearing formation would probably prove to be Silurian and 

 Devonian. 



1859. Sir R. Murchison also thought that these rocks were Paleozoic, 

 mostly Silurian. t The work of Dr John B. Trask J in finding Carbonif- 

 erous fossils in the metamorphic rocks of Shasta county seemed to con- 

 firm these opinions, for the McCloud river rocks are almost in the pro- 

 longation of the strike of the Auriferous slates of the Sierra Nevada. L. 

 Simonin § claims to have found trilobites in the slates, but does not give 

 the locality. J. Marcou || says that they were found in Mariposa count}^ 

 and were preserved in the museum of the University of Santiago, Chile. 



1864. The first reference of the Auriferous slates to other than Paleo- 

 zoic age was made by J. D. Whitney ,*[[ who said that they consisted 

 largely of Trias and Jura. This was based on the finding of undoubted 

 Triassic and Jurassic fossils in Indian valley, Plumas county, and of 

 rather uncertain Jurassic fossils on the Mariposa estate, Mariposa county. 



1865. F. B. Meek afterward published ** descriptions and figures of the 

 Jurassic fossils of the Mariposa slates. Whitney ft refers to the finding 

 of Goniatites (^Celtitesf) Isevidorsatus, Gabb (not Hauer), in Tuolumne 

 county between Knight's and Robinson's ferries on Stanislaus river, at the 

 mouth of Mormon creek, and in Eldorado county at Spanish Flat. On 

 this evidence, together with the finding of Upper Trias near Taylorsville, 

 Plumas county, he refers part of the Auriferous slates to the Trias. 



1870. W. M. Gabb^ published the opinion that all the Jurassic deposits 

 of the Sierra Nevada and their vicinity were probably of Liassic age. 

 1 876. J. F. Whiteaves §§ thinks that Aucella erringtoni is the equivalent 



* Pacific Railroad Report, 1858, Introduction, p. iv. 



t Murchison : " Siluria," third edition, 1859, pp. 455 and 475. 



X Report on the Geology of the Coast Mountains, 1855. 



gComptes Rcndus, tome L, 1860, p. 391. 



II Bull. Soc. Geol. France, 1883, p. 409, 



^ Am. Jour. Sei., September, 1864, p. 261. 



** Geology of California, vol. i, Appendix B. 



ft Paleontology of California, vol. i, p. 279. 



JJAm. Jour. Conch., vol. v, p. 5. 



§§Geol. Survey of Canada, Mesozoic Fossils, vol. i, part i, p. 86. 



