TERTIARY PERIOD. 



505 



the junction of the same with the Cretaceous. The whole low-coun- 

 tries of the Southern Atlantic States and the whole of Florida were then 

 a sea-bottom. The Gulf of Mexico was far more extensive than now, 

 and especially it sent a wide bay northward to the mouth of the Ohio- 

 The Mississippi Kiver below that point did not then exist. The Ohio, 

 Arkansas, and Red Rivers emptied by separate mouths into the embay- 

 ment of the Gulf. 



This was at the beginning. During the course of the Tertiary the 

 shore-line was gradually transferred eastward along the Atlantic, and 

 southward along the Gulf, as shown by the dotted lines introduced in 

 the Tertiary areas in the map on page 291. 



In the interior, in the region of the Plains, the Plateau, and the 

 Basin, there were at different times immense fresh-icater lakes. The 

 places of some of these are indicated on map, Fig. 844,, in dotted out- 



Fig. 844.— Map of Tertiary Times, showing Outline of Coast and Places of Principal Tertiary Lakes. 



line. These outlines, however, are not intended to be accurate. These 

 lakes drained some of them into the Mississippi, some into the Colo- 

 rado, and some into the Columbia River. 



The Pacific shore-line at that time was along the foot-hills of the 

 Sierra Range, and therefore the whole region occupied by the Coast 

 Ranges and the Sacramento and San Joaquin Valleys, and also portions 

 of Western Oregon, were then a sea-bottom. These facts are roughly 

 represented on map, Fig. 844. The positions of the principal mount- 

 ain-chains, e. g., Sierra, Wahsatch, Uintah, the eastern border of the 



