THE TERTIARY PERIOD 



The Pliocene Epoch 



The term Pliocene is from the Greek pleion, more, and kainos, 

 and refers to its close approximation to the present order of things. 



American. — The Pliocene is not a conspicuous formation in 

 this country, and only of late years has it been recognized at- all 

 on the Atlantic coast. The movements which closed the Miocene 

 gave to the Atlantic and Gulf shores nearly their present outlines, 

 but some differences may be noted. Much of southern Florida 

 was still under water, and a gulf invaded northern Florida, cover- 

 ing a narrow strip of Georgia and South Carolina. Isolated patches 

 of Pliocene rocks in North Carolina and Virginia may be remnants 

 of a continuous band. A small part of eastern Mexico, much of 

 Yucatan, and some of Central America were still submerged. 



On the Pacific coast the post-Miocene upheaval had laid bare 

 the western foot-hills of the Sierra and greatly disturbed the Mio- 

 cene strata of the Coast Range. This range sank again early in 

 the Pliocene, whose strata lie unconformably upon the Miocene, 

 and extend over upon older beds. The transgression of the sea 

 was limited, and Pliocene rocks form only a narrow band along 

 the coast in California, Oregon, and Washington. The San Fran- 

 cisco peninsula was an area of subsidence and maximum deposi- 

 tion, for here no less than 5800 feet of sandstone (the Merced 

 series) were formed, the thickest mass of Pliocene in North 

 America. The mountains of British Columbia are believed to 

 have been at a higher level than now, an elevation which probably 

 connected Vancouver's and the Queen Charlotte Islands to the 

 mainland. Marine Pliocene also occurs in southern Alaska. 



In the interior are a number of Pliocene lake basins, the out- 

 lines of which have not yet been determined. The oldest of these 

 formations is the Goodnight stage, named from a locality in Texas, 

 where the beds lie unconformably upon the Nebraska substage of 

 the Loup Fork. Similar beds have been found in northern Kansas 

 and eastern Oregon, where they are closely connected with the 

 Nebraska and followed them after no long interval. The second 

 stage of fresh-water Pliocene is the Blanco, which extends over 



