STRATIGRAPHY OF THE SKYKOMISH BASIN 563 



Miss Caroline A. Duror, in another part of this paper, has 

 identified the following fossils as of Ordovician age: Rafitiesquina 

 deltoidea and Illaenus americanus. This is the first recorded evi- 

 dence of the presence of Ordovician strata in the Cascade Moun- 

 tains of Washington, and both fossils are the first of their kind of 

 Paleozoic age to be found there. With this Ordovician series 

 begins the definitely known geologic history of the Skykomish 

 Basin. It was a period during which the area stood approximately 

 at sea-level, as evidenced by the fact that the limestone lenses 

 carry marine fossils. The presence of quartzite shows that prob- 

 ably the area was not deeply submerged, but more probably was 

 near the continental margin. There is no record of the post- 

 Ordovician Paleozoic. 



MESOZOIC 



There are no Mesozoic deposits at present, though there is 

 evidence that they must have existed. The sole known event of 

 the Mesozoic in the Skykomish Basin is the intrusion of batho- 

 lithic igneous rocks whose structural relations identify them as 

 Mesozoic, though there is no other positive evidence of their age. 

 But it is altogether probable that the batholiths were intruded as 

 a part of the great Sierra Nevada intrusion identified in California 

 and Oregon as of Jurassic age. Daly, Smith and Calkins, Russell, 

 Weaver, and others assert this probability. The granodiorite of 

 which this batholith is composed is granitoid in texture, and such 

 a texture can be established only under a thick cover of super- 

 jacent rock. This cover was removed in post- Jurassic time, leaving 

 the batholith uncovered at the end of the Mesozoic. Russell 1 and 

 Smith 2 have described sedimentary rocks of Cretaceous age, from 

 Whatcom County to the north, and it is therefore inferred that 

 removal of the 2,000 feet or more of the cover of the Jurassic 

 batholith was toward the north. The series, as described by Smith, 

 under the name Pasayten, begins with a conglomerate in which 



1 1. C. Russell, "Cascade Mountains in Washington," 20th Ann. Rept. U.S.G.S., 

 Part II (1898), p. 114; G. M. Dawson, "Geological Record of the Rocky Mountains 

 in Canada," Bull. Geol. Soc. Am., XII (1901), 84. 



3 Smith and Calkins, "Cascade Mountains in Washington," 20th Ann. Rept. 

 U.S.G.S., Part II (1898), p. 114. 



