138 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



The McCloud shales (Nosoni formation) are provisionally correlated 

 with the upper Hueco by Girty, and Schuchert 1 remarks: " It also seems to 

 correlate with the Schwagerina zone of the Russian geologists. This zone 

 is just below the Perrno-Carboniferous or Artinskian." 



They are described as the lower part of the Pitt formation by J. P. Smith, 

 as follows: 2 



"The Pitt formation overlies conformably the McCloud limestones, and 

 consists roughly estimated of about 3,000 feet of siliceous and calcareous shales, 

 conglomerates and tuffs. * * * 



"The oldest fossiliferous strata of the Pitt formation are of Upper Carbonifer- 

 ous age. * * * The rock is a dark calcareous argillite. * * * These beds are the 

 probably equivalents of the Robinson beds of the Taylorsville region, and of the 

 Little Grizzly Creek beds, Plumas County, which seem to form the top of the 

 Carboniferous formation. The boundary of these Carboniferous argillites could 

 not be found, but they probably make up the lower thousand feet of the Pitt 

 formation." 



Diller, in the Redding Folio, says that the McCloud limestone was 

 formed by quiet sedimentation during Mid-Carboniferous time, that oscilla- 

 tions began and the McCloud was succeeded in Nosoni (late Carboniferous) 

 by shales and sandstones with increasing quantities of tuffs and volcanic 

 flows. The period of deposition was terminated in this locality by an 

 uplift and extensive volcanic activity. 



In the Klamaths proper the McCloud is a fine-grained limestone, very 

 siliceous in places; it is upper Carboniferous and equivalent to the Caribou 

 of the Plumas County region. 



The Nosoni shale is continued above the McCloud and is overlain by 

 the Hall City limestone of Permian age. 



Girty 3 correlated the McCloud limestone with the Hueco. Both Girty 

 and Schuchert have suggested that the same sea which deposited the 

 McCloud extended into southwestern British Columbia (Cache Creek), and 

 into Alaska as far as the Chicagoff Islands. 



The deposition of the Nosoni was terminated all along the Pacific coast 

 by an elevation which was the culmination of the volcanic activity which 

 furnished the tuffs and flows of the Nosoni. This elevation probably repre- 

 sents a considerable interval of time before the deposition of the Triassic. 

 It was in all probability a part of the greater movement which is traceable 

 from Alaska southward, in elevation and extensive volcanic activity both 

 subaerial and submarine (southern Alaska) as far as the Redding, Cali- 

 fornia, quadrangle. 



1 Schuchert, Chas., Paleogeography of North America, Bull. Geol. Soc. Amer., vol. 20, p. 



573. 1910. 



a Smith, J. P., loc. cit., p. 601. 

 3 Girty, Geo. H., The Relations of Some Carboniferous Faunas, Wash. Acad. Sci., vol. 7, 



p. 16, 1905. 



