780 GEOLOGY 



too thick to be subaerial; but it is not apparent that it is more 

 difficult to acount for thick subaerial sediments, under the con- 

 ditions indicated, than to account for thick lacustrine or marine 

 formations. 



The relations of the Eocene beds of the western interior are 

 such as to indicate that both the attitude and altitude of the sur- 

 faces in that part of the continent were very different from those 

 which now exist. That region must have been much lower than 

 now, and, locally and temporarily at least, without well-established 

 drainage. The present mountains were certainly not so high as 

 now, though considerable elevations and great relief doubtless 

 existed. 



Close of the Eocene in North America. The closing stages of 

 the Eocene were marked by crust al movements in the west, result- 

 ing in considerable changes in geography. Such movements had 

 been in progress throughout the period, as has been indicated; but 

 the changes at the close were on a larger scale. The deformative 

 movements seem to have included both faulting and folding. The 

 result was the retreat of the sea along the Pacific coast, the develop- 

 ment of new areas of high and low lands, and therefore a shifting 

 of the sites of rapid degradation and aggradation. Outside the 

 Cordilleran region the changes were less. 



Along the Atlantic and Gulf coasts the Miocene is in many 

 places unconformable on the Eocene, and it was at the close of the 

 Eocene (or perhaps during the Oligocene) that an island, now in- 

 cluded in the peninsula of Florida, was formed. In the Carolina-, 

 and in the western Gulf region, the conformity between the Eocene 

 formations and those classed as Oligocene seems to preclude notable 

 changes of geography along the coast in the southeastern part of 

 the United States at the close of the period. 



FOREIGN 



Europe. Considerable lakes, estuaries, and perhaps other 

 areas of deposition remained over western Europe within the are! 

 from which the sea withdrew, at the close of the Meso/oir era. 

 Later, but still early in the Eocene, submergence of the land set in. 



