SILURIC OR OXTARIC PERIOD 



539 



later a general subsidence was in progress in the Hudson sea, and finally 

 the greater part of the American continent became emergent. This was at 

 the beginning of the Salina group, and from this time to the close of the 

 Siluric the continental seas were North Atlantic in origin, their extension 

 being restricted to the northern Appalachian and the Saint Lawrence seas. 



The seas of Cayugan time in the main were not normal marine waters. 

 They were shallow pans, in which locally red and black shales, with salt, 

 gypsum, and water limestones, were deposited. The life was Atlantic in 

 origin, the principal eurypterids and ceratiocarids having marked rela- 

 tionship with those of Scotland and Wales, and to a lesser degree with 

 those of the Baltic area. Even in the Saint Lawrence trough, the de- 

 posits of this time are as devoid of life as those of the Appalachian sea. 



Toward the close of the Siluric in the Monroe group normal marine 

 conditions gradually became dominant, and there was an appearance of 

 life prophetic of the Helderbergian of the Devonic. The various forma- 

 tions of the Cayugan series are as follows : 



Table of Cayugan Formations 









m 





<0 









5h 



o . 



d> 



° a 



m 



*H r? 







d 



o 2 



03 



bo 



S M 



d 





>> 





oi 







U 



ft 













o 





r-\ 





S£ 





03 





d 













03 





m 



New York 



Western New York Eastern New York 



Bertie, 60 feet 

 Camillus, 50-300 feet 

 Syracuse \ fi00 f , 

 Vernon f bUUleet 

 Pittsford, 20 feet 



Manlius. 75 feet 

 Rondout, 40 feet 

 Cobleskill, 6 feet 



Rosendale 

 Wilbur 

 Binnewater 

 High Falls 

 Shawangunk 



Michigan and western On 



tario (Grabau, Jour. 



Geol., 1909) 



Lucas 



Amherstburg I Upper 

 Anderdon f Monroan 

 Flat Rock J 



During the Siluric there was much land throughout the Eocky Mountain 

 region, from Mexico into the Arctic area, and it was only on the eastern 

 side of this land that the Pacific spread into the Cordilleran sea by way 

 of the Great Basin and the Arctic ocean. In the Sonoran sea, at El Paso, 

 Texas, there was another Siluric transgression. Of these western faunas 

 little is as yet known. Kindle 158 reviews all the known Eocky Mountain 

 occurrences. In California a few Siluric fossils have been found in the 



158 Kindle : American Journal of Science, vol. 25, 1908. 



