I9I3] STRATIGRAPHY OF PACIFIC COAST OF AMERICA. 567 



The Chehalis Formation. 



The term Chehalis sandstone was used by Lawson^^ for some 

 arenaceous bedded tuffs containing marine Eocene fossils exposed 

 in a water tunnel through the hill east of the city of Chehalis, 

 Washington. The beds here form an intregal part of the south limb 

 of an anticline in which several thousand feet of conformable strata 

 are involved, the friable nature of the rock rendering an exact 

 estimate of the thickness difificult without instrumental measure- 

 ments. The upper beds exposed by this anticline are distinctly 

 marine while the lowest are probably of freshwater origin judging 

 by the presence of workable coal seams. 



This anticline is in turn one of a series of folds whose axes 

 have a general east-west trend, exposed along the lower slopes of the 

 Cascade Range east of the Portland-Tacoma railway from a few 

 miles south of the Cowlitz River northward to Tenino. Upwards 

 of 10,000 feet of bedded tuffaceous and lignite-bearing sandstones 

 and shales, to a large degree of estuarine or freshwater origin, but 

 with frequent local zones of marine fossiliferous sediments, are 

 involved in this folding. 



Other areas of the Chehalis formation are the Balch syncline 

 west of Chehalis and Centralia, the King County coal fields extend- 

 ing from Allentown in the Duwamish Valley eastward and south- 

 ward beneath the glacial drift to Renton, Green River, Newcastle, 

 and Squak Mountain, and the lowest 2,000 feet of Eocene in the 

 Pierce County coal field, the beds in which the Fairfax and Monte- 

 zuma mines are located. 



No equivalent strata have been recognized elsewhere in the north- 

 west but the Tejon of the type locality near old Fort Tejon in 

 California evidently represents the same faunal stage. In many 

 respects the Chehalis fauna is similar to that of the succeeding 

 Olequa formation, but the floras are markedly different, that of the 

 Chehalis formation lacking the distinctly tropical facies of the later 

 divisions of the Tejon, and thus affording a most characteristic 

 feature. 



^^Ain. Geo!., XIII., 1894, P- 437- 



