314 University of California Publications in Geology [Vol. ll 



cherts from the Calaveras in the area of the Grass Valley Special 

 Map. He regarded them as replacements of limestone : 



The area along the western margin of the district consists of grayish, not very 

 fissile clay slates, alternating with much white or light colored chert, breaking in 

 small, sharp, angular fragments. 



This chert is probably derived from limestone by a process of silicification. 

 There are no outcrops of limestone within the area, yet the peculiar bowl-shaped 

 depression on the top of the ridge 2500 feet northwest from the North Star Mine, 

 known as the ' ' Devil 's Punchbowl, ' ' can be explained only as a collapsed cave 

 formed by the leaching out of limestone mass. 



Bedded cherts are reported five miles west of Coulterville. 54 They 



are also found on the southwest slope of Hunter Mountain, where 



they are associated with tuffs. 



WASHINGTON 



Bedded radiolarian cherts are known also in the Peshastin forma- 

 tion in the state of Washington. 55 The age of this formation is not 

 certainly known, other than that it is pre-Tertiary. On account of 

 the considerable amount of deformation and intrusion which has 

 affected it, it is regarded as Paleozoic. Weaver states that it is some- 

 what similar to rocks of the Calaveras formation of the Sierra Nevada, 

 and that it is also somewhat similar to the Cache Creek series in 

 British Columbia. It is therefore provisionally referred to the Car- 

 boniferous. 



The Peshastin formation is predominantly composed of black 

 slates and fine grained, dark colored quartzites. It contains occa- 

 sional bands of red and green radiolarian chert. It is cut by serpen- 

 tine and other basic eruptives and also contains amphibolitic schists. 

 In the Mount Stuart quadrangle, Smith describes some of these schists 

 as glaucophane schists. In the Snoqualmie quadrangle there are blue 

 schists, said to owe their color to the presence of graphite in green 

 amphibole. 



ALASKAsc 



In the region around Cook Inlet and Prince William Sound, in 



54 Mother Lode District, U. S. Geol. Surv. Folio no. 63, p. 4, 1900. 



ss Smith, G. O., Mount Stuart Folio, U. S. Geol. Surv. Folio no. 106, 1904. 



Smith and Calkins, Snoqualmie Folio, ibid., Folio no. 139, 1906. 



Weaver, C. E., Washington Geol. Surv. Bull. 6, 1911. 



so Palache, C, Harriman Alaska Expedition, vol. 4, pp. 26, 27, 56, pi. 2. 



Stanton and Martin, Mesozoic Section on Cook Inlet and Alaska Peninsula, 

 Bull. Geol. Soc. Am., vol. 16, p. 391, 1905. 



Grant and Higgins, Eeconnaissanee of the Geology and Mineral Eesources 

 of Prince William Sound, U. S. Geol. Surv. Bull. 443, 1910. 



Martin and Katz, A Geologic Eeconnaissanee of the Iliamana Eegion, U. S. 

 Geol. Surv. Bull. 485, 1912. 



Martin, Johnson and Grant, Geology and Mineral Eesources of Kenai 

 Peninsula, Alaska, TJ. S. Geol. Surv. Bull. 587, 1915. 



