POST-TERTIARY PERIOD. 547 



2. CHAMPLAIN EPOCH. 



American. 



The Champlain epoch is so named from beds of the epoch on the 

 borders of Lake Champlain. 



The term Champlain is applied to marine deposits of the epoch by Hitchcock 

 in the Keport on the Geology of Vermont. 



I. Rocks : kinds and distribution. 



Distribution. — The distribution of the formations of the Champlain 

 epoch may be treated of under three heads : (a) river-border forma- 

 tions ; (6) lake-border and other lacustrine formations; (c) marine 

 or sea-border formations. 



(a.) River-border formations. — From New England to California and 

 Oregon, over the wide range of the continent, the river-valleys 

 contain extensive alluvial formations. The beds overlie the drift 

 of the Glacial epoch, where they occur together, as has been ob- 

 served in several places ; and they generally reach to a height far 

 above that of present alluvial action. The Connecticut Eiver, 

 Hudson, Mohawk, Ohio, Sacramento, Willamette, and numerous 

 other valleys afford fine opportunities for their study. 



The formation along the course of any river has nearly a flat 

 summit, and is the foundation of the elevated plateau of the 

 valley ; and very often there are plains at one or more levels besides 

 the upper, so that the whole makes a series of terraces. 



The sketch on p. 548 (fig. 830), from the Connecticut Eiver valley 

 some miles south of Hanover, N.H., represents the general appear- 

 ance of the alluvial formation with its terraced surface. The de- 

 scents of a road in the neighborhood of rivers are mostly from the 

 top of one of the tables down to the bed of a streamlet, the origin, 

 perhaps, of the cut ; and the ascent on the opposite side carries the 

 road to the upper level again. The borders of all such cuts, there- 

 fore, and of river-valleys generally, are excellent places for observ- 

 ing the features of the alluvial landscape and studying its beds. 

 Up or down the stream, horizontal lines may often be traced for 

 miles, marking the limit of one or more of the several terraces bor- 

 dering it. Many villages in the vicinity of rivers owe a large part 

 of the beauty of their sites to these natural terraces of the country. 



This alluvial formation appears to characterize all the river-val- 

 leys of the continent over the drift -latitudes, and also, to a less 

 extent, still farther south in the latitudes of Kentucky and Ten- 



