45 8 STUDIES FOR STUDENTS 



The Puget formation consists of interbedded sandstones, shales and coal 

 beds aggregating 10,000 feet or more in thickness. Sandstones prevail. 

 They are of variable composition, texture, and color, and are frequently cross 

 stratified. Their composition ranges from a typical arkose, consisting of 

 slightly washed granitic minerals to siliceous clays. The separate beds vary 

 from a few inches to more than 100 feet in thickness. Conglomerates and 

 concentrated quartz sands have not been observed. The variations in color 

 are not such as to distinguish upper and lower sections of the formation. In 

 general the strata are similar and are similarly interbedded from top to bot- 

 tom. 



The shales pf the Puget formation are formed of siliceous clayey muds 

 •containing sometimes considerable carbonate of iron, and generally more or 

 less carbonaceous matter, which varies in character from finely divided 

 organic material to large leaves and stems 



Carefully measured sections show that the Puget formation contains more 

 than 125 beds which would attract the attention of a prospector searching for 

 coal. They range from one to sixty feet in thickness, and the workable coal 

 beds in any one section vary from five to ten in number. The valuable coal 

 is found in the lower 3000 feet of the formation as at Carbonado, Wilkison, 

 Burnett and Green River. 



The Puget formation contains an abundant flora. Fossils are 

 found throughout the Puget formation. These are brackish- 

 water forms. No marine forms have been found in the Puget beds. 

 Willis thinks the beds were laid down in an estuary in which the 

 northern Cascade range formed a peninsula, and the Olympic 

 Mountains an island. 1 



In 1895-6 Willis made collections "from definitely deter- 

 mined stratigraphic horizons on Green River, above , Burnett, on 

 South Prairie Creek, and on Carbon River near Carbonado. A 

 preliminary examination of the fossil plants enables Knowlton 

 to report that the lower beds of the series are Eocene, whereas 



the upper beds may be of Miocene age The measured 



sections of the Puget series exhibit a total thickness of 5800 

 feet on Green River, 5500 feet on South Prairie Creek, and 5480 

 feet in Carbon River Canyon. None of these measures is com- 

 plete The sections probably overlap " 2 



1 Cf. Clark : loc. cit., p. 197. 



2 Willis : Bull. Geol. Soc. Amer., Vol. IX, pp. 5, 6, 1898. 



