PHYSIOGRAPHIC CHARTS 



249 



At the close of the whole revolution the continental land outlines dif- 

 fered very little from those immediately preceding the Saint Peter epoch. 



Paleogeogeaphic Charts 



Following out the conclusions involved in the foregoing discussion, the 

 accompanying physiographic charts are presented (see figures 5 and 6). 

 They are an attempt to indicate the land and sea distribution for the 

 Mississippi valley in Saint Peter time. The 



ines drawn are genera 1- 



Fiuure (j. — Continental Outline near close of Saint Peter Time. 



izations and do not aim at local precision. It is intended to be under- 

 stood that a maximum land area existed in mid- Saint Peter time, 

 followed by a rapid encroachment of the sea to a coastline very like its 

 pre-Saint Peter position. 



The maximum retreat is drawn arbitrarily as interpreting the change 

 of character of sediments from offshore to deep-sea types. In the absence 

 of data northward beyond the present limits of the formations involved, 



