638 



NEW YORK STATE MUSEUM 



Barriers 



named 



northern parts, the eastern one in the middle part of the Appa- 

 lachian valley, they constituted, if we except the Normans kill 

 and Utica transgressions and the Devonic intervals of local sub- 

 mergence, an effective barrier between the interior continental 

 or Mississippian sea and the Atlantic, to the final emergence of 

 the entire Appalachian region. 



The western of these two folds, whose geographic position is 

 indicated on the accompanying map, we shall call the Appalach- 

 ian valley barrier or fold, while the eastern is called the Chilhowee 

 barrier or fold, when we refer to the middle portion and lower 

 end of the uplift, and the Green mountains barrier in speaking of 

 its northern &nd. 



Coincident with the emergence of these folds, the Mississip- 

 pian sea was restricted to narrower limits, but at present it is 

 not safe to indicate the extent of the land areas then formed. 

 Still it seems certain that, with the exception of the Chazy 

 basin and Levis channel defined in the following paragraphs, all 

 of New York was above sea level. 



The space between the two folds we shall refer to gen- 

 erally as the Appalachian valley trough or simply Valley 

 vaiiey trough t mU gh, and, in order to facilitate reference and geographic 

 accuracy, it is divided into three unequal parts. The 

 southern third, extending from Alabama to southwestern Vir- 

 ginia, we shall refer to as the Lenoir basin, the middle third, 

 extending on to New Jersey, forms part of the subsequent Cum- 

 berland basin, and the northern third, extending as far as New- 

 foundland, will be called the Levis ohannel. Parallel with, but 

 shorter than the Levis channel, and immediately northwest of 

 the Appalachian valley barrier, lies the Chazy basin, with its 

 typical Chazy deposits and fauna. 



As will be seen later, these divisions are distinct though in- 

 definitely bounded basins, of which the central one was com- 

 monly occupied by the Mississippian sea, while the terminal 

 basins were generally taken up by Atlantic waters. 



Immediately following the emergence of the folds and the 

 broader land area just mentioned, there began a period of sub- 



