THE EOCENE PERIOD. 



203 



enough to attract prospectors. They range from one to sixty feet 

 in thickness. Most of the workable coal is in the lowest 3000 feet 

 of the series. The Eocene period in this region seems to have been 

 one of interrupted submergence. The area of deposition extended 

 south into western Oregon, and as far east as the Cascade mountains. 

 In the Coos Bay region of Oregon, the Coaledo formation (Fig. 419, , 

 like the Puget formation farther north, contains workable beds of coal 

 and many beds containing brackish-water fossils. 1 



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Fig. 421. — Map showing the position of known coal-bearing formations in Alaska. 

 The coal of the Yukon basin is partly Cretaceous and partly Tertiary; that 

 of southeastern and southwestern Alaska, chiefly Eocene, that of the north- 

 west coast, Mesozoic. South of Cape Lisburne there are outcrops of Paleozoic 

 coal-bearing formations. There is also much lignite of post-Eocene age. (Brooks, 

 U. S. Geol. Surv.) 



North of Washington. — British Columbia appears to have been 

 land during the Eocene period, and the erosion there in progress resulted, 

 by the end of the period, in a peneplain which has since been elevated 

 2000 to 3000 feet. 2 Eocene beds, much disturbed, have been recog- 

 nized in Alaska, 3 where they are sometimes coal-bearing. 



1 Diller, Coos Bay, Ore., Folio, U. S. Geol. Surv. 



2 Dawson, Science, Vol. XIII, 1901, p. 401. Also Spencer, A. C, Bull. Geol. Soc. 

 of Am., Vol. XIV, p. 131. 



s Dall, Tertiary Fauna of Florida, Trans. Wagner Free Inst., Vol. Ill, Pt. VI, 

 1903, p. 1548. 



