cenozoic time — quaternary. 981 



2. Champlain Period. 



AMERICAN. 



The Champlain period is so named from the occurrence of beds of the 

 period on the borders of Lake Champlain. 



The term Champlain was first used by C. H. Hitchcock, in the Report on the Geology 

 of Vermont (1861), for the marine beds of the period occurring along the lake, and for 

 similar beds in the St. Lawrence valley, as a substitute for the term, "Laurentian 

 deposits," applied to the latter by DesOr. The author, in a paper, in 1856, adopted the 

 latter name ; but as Laurentian was earlier given by Logan to a subdivision of the 

 Archfean, Champlain was substituted in the first edition of this work (1863). 



The prominent events of the period are : (1) the completion of the sub- 

 sidence begun in the closing part of the Glacial period ; (2) the subsidence 

 over large areas, greatest to the north ; (3) the disappearance of the ice that 

 remained on the mountains and elsewhere within the borders of the United 

 States, and finally from the Canadian ice-plateau, completing the deglacia- 

 tion of the continent; (4) a change of climate to one even warmer than 

 that of Recent time ; (5) the conversion of many of the southward flowing 

 streams, that were eroding streams in the Glacial period, into feebly mov- 

 ing and feebly working streams, and the making of lakes ; (6) the rapid 

 growth of vegetation, covering hills, mountains, and prairie regions with the 

 greatest of forests. A moister climate than the present is rendered probable 

 by the greatly increased surface of fresh waters in lakes and rivers over the 

 continent, as well as by the greater warmth of the climate. 



The Champlain has been sometimes designated the Pluvial period, to mark 

 its contrast with the Glacial period. 



THE SUBSIDENCE. 



1. Kind of evidence. — Evidence of the subsidence is found on the borders 

 of the continent in elevated shore-lines of the Champlain period, as beaches, 

 shell-beds, seashore flats, rock planulations or terraces ; and over the interior 

 of the continent in the existence of lake-basins that were occupied by Cham- 

 plain lakes, some of them exceeding in size any modern lake. 



2. Amount over the eastern Continental border. — The subsidence increased 

 in amount over eastern America from the south, northward, and also from 

 the seashore, landward. The difference between the level of the Champlain 

 period and the present as indicated by shore-lines, terraces, shell-beds, and 

 other evidence is about as follows at the places mentioned : on the southern 

 shores of ISlevv England, near New Haven, 20 feet ; shell-beds in deposits at 

 Sancati Head, on Nantucket, 80 feet ; on the coast of Maine, as proved by 

 fossils, 150 to 300 feet ; the upper benches at Mount Desert, Me., 270 to 300 

 feet (Shaler). 



Along the north and south valley of the Connecticut, terraces increase in 



