STRATIGRAPHY OF THE SKYKOMISH BASIN 565 



disturbance left the area adjacent to the Skykomish Basin on the 

 east in a condition sufficiently elevated to make the earliest Tertiary 

 a period of erosion. 



III. TERTIARY 



EOCENE 



In the Skykomish area the Eocene was a period of sedimenta- 

 tion during which 4,000 feet of arkoses, shales, and conglomerates 

 were deposited. About the middle of the series there are two shale 

 formations which yield a considerable flora. The series is directly 

 continuous with the Swauk series of the Snoqualmie quadrangle, 

 and is also related to it on paleontologic grounds. It outcrops in a 

 belt several miles in width, striking approximately N. 45 W. in 

 the Eagle Creek-Beckler and the Foss River valleys. The dips 

 vary; in the measured section, half a mile south of the Great 

 Northern Railway, the base of the series lies nearly level, with 

 increasing dip to the east as one goes east, and to the west as one 

 goes west, until the top of the series stands vertical. It is an 

 anticline whose basal beds rest unconformably on Easton schist, 

 and whose roof is a part of the Keechelus andesite series. 



Miss Duror's appended report is made on the flora collected 

 from two horizons about 600 feet apart vertically, the lower being 

 1,100 feet from the base of the Swauk. Fossils numbered F 831, 

 F 831+50, and F 844 are from the upper beds; those numbered 

 F 865 from the lower. With the latter is associated a coal bed 

 some 14 inches thick on which slopes have been driven in the hope 

 of finding minable coal. 



The sandstones and conglomerates are cross-bedded and the 

 fragments usually angular and never assorted (Fig. 1). It has 

 been considered a fresh-water lake deposit. In the light of the 

 recent developments of stratigraphy it may better be classed as 

 in part purely continental and in part deposited by streams, prob- 

 ably in deltas. The shales, and particularly those carrying complete 

 specimens of Sabal, could only have been laid down in situ and 

 must have been formed in shallow water — probably in a swamp. 

 None of the series bears evidence of deposition in deep water, and 

 both the angular condition and the considerable size of the frag- 

 ments forbid their having been transported for any great distance. 



