ORDOVICIC PERIOD 529 



lith reworked by the sea of the succeeding transgression? Such being 

 the case, these reworked sandstones must be referred to the Ordovicic 

 system. 



Ordovicic Period (new emendation) 



(In part the Ordovician of authors) 



For the detailed descriptions of the various formations of this system 

 see Ulrich's paper, and for the areal distribution of the seas the five 

 maps — (1) Stones Kiver-Chazy, (2) Lowville, (3) Lowest Trenton, (4) 

 Late Trenton, and (5) Utica (plates 56-60). Also see pages 486, 487. 



Table of Ordovicic Formations 



Utica of New York. Mastigograptus fauna. 



Trenton of New York. In the main, Galena of Iowa, Illinois, etc. 

 In the Atlantic province, the Climacograptus caudatus, Cory- 

 noides curtus, and Magog graptolite zones. 



I K!mm Gi*e r a lly" n btakheri SS0Uri - 1 The horizon of the Nor " 



Generally a break here. J of the Atlantic P rovlnce - 



Lowville of New York. Represented in Moccasin of Tennessee. 



Generally a break here. 

 Upper Chazy of the Champlain valley. This horizon is included 

 in the Holston of Tennessee, 800-900 feet thick. . Plattville of 

 Chazian . . . . -{ Wisconsin = Carter or top of Upper Stones River. 



Stones River (Lower and Middle) of the Southern states. Lower 

 and Middle Chazy of the Champlain valley. 

 General break. 

 Canadic period. 



The Saint Peter emergence of the Canadic period was followed by a slow 

 and very decided transgression of the sea. The invasion, however, was 

 highly oscillatory, moving in and out of the areas, yet in general the suc- 

 cessive floods were greater and greater, and finally in Trenton time was 

 developed the greatest inundation that had ever covered the North Ameri- 

 can continent. More than one-half of its area and somewhat less than 

 two-thirds of the United States were then under the sea. Here again the 

 Appalachian-Acadian land barriers were effective in preventing the inter- 

 mingling of the Pacific and Atlantic faunas. The life in the Pacific, 

 however, now took on a more cosmopolitan character, which was in all 

 probability due to the mixing of the Pacific elements with those of the 

 Arctic region, for at this time occurred the first northern Paleozoic inun- 

 dation. Very similar faunas are found in Baffin Land, Manitoba, Minne- 

 sota, New Jersey, and Tennessee. Today the Arctic is regarded by 

 oceanographers as but a part of the Atlantic, but in Ordovicic times it had 

 little communication with that ocean, and many of the Black Eiver, 

 Trenton, and Eichmond fossils remind one of those of the Baltic region, 



