248 GEOLOGY. 



The marine Oligocene is also represented in western Oregon x (Aturia 

 and Astoria beds), and the earliest Tertiary deposits of British Columbia 

 (non-marine) are now referred to the Oligocene. 2 They contain some 

 coal, and antedate the Tertiary volcanic activity of the region. 



Beds referred to the Oligocene are wide-spread in Alaska, 3 where they 

 are sometimes carboniferous, and little disturbed. Here belongs the 

 • thick Kenai series (said to be 10,000 feet) unconformable on Eocene. 4 

 Certain fossiliferous beds of western Greenland seem to be of the same 

 age as the Kenai series. 



Considerable geographic changes occurred during the Oligocene, or 

 at its close, especially in the Gulf and Carribbean regions. 5 In both 

 regions, the Oligocene (early Oligocene) beds are commonly conforma- 

 ble on the Eocene and unconformable beneath the Miocene; and in 

 the latter, there was a notable deformation and increase of land during 

 the Oligocene or at its close. 



The biological effects of the physical changes about the Gulf of 

 Mexico and the Carribbean Sea at about this time have already been 

 referred to. 



Foreign. 



Europe. — The Oligocene is more distinctly differentiated from the 

 Eocene in Europe than in most parts of America. Toward the close 

 of the Eocene, the epicontinental sea of northern Europe was excluded 

 from some areas which it had covered during that period, but the 

 changes which converted the Eocene areas of deposition into land were 

 probably slight, since after their occurrence considerable areas stood so 

 near sea-level that slight changes of altitude served to greatly restrict or 

 extend the epicontinental waters. How far the restriction of the sea 

 at the close of the Eocene was the result of surface warping, and how 

 far the result of the filling of shallow basins with sediment, is unknown. 



At the beginning of the Oligocene period, the sea transgressed con- 

 siderable areas of Germany which had been land in the Eocene period. 



1 Dall, op. cit., and Diller, 17th Ann. Rept. U. S. Geol. Surv. 



2 Dawson, Science, March 15, 1901. 



3 Schrader, Bull. G. S. A., Vol. 13, p. 248, and Brooks, p. 261. 



4 Dall, Trans. Wagner Free Inst., Vol. VI, 1903, p. 1548. See also Dall, 18th 

 Ann. Rept. U. S. Geol. Surv., Pt. II, and Spurr, Pt. III. • The Kenai formation was 

 formerly classed as Eocene. 



5 See references to the writings of Hill under Eocene. 



