128 NEW YORK STATE MUSEUM 



and the greater part of the interior Siluric sea into a vast partially 

 or entirely inclosed basin. This elevation appears to have been 

 accompanied by climatic desiccation which brought about 

 a rapid evaporation of the waters and a consequent increase in 

 salinity. Thus this great interior water .body was changed from, a 

 richly peopled mediterranean, to a lifeless body of intensely saline 

 water^ a veritable Dead sea. As the concentration of the brine con- 

 tinued, deposition of gypsum began, and later on the extensive beds 

 of rock salt of this formation were laid down. Some of these salt 

 beds in Michigan are reported to be a thousand feet thick^ 

 but none of the New York beds approach this thickness. The clas- 

 tic strata of the Salina series were probably derived from the de- 

 struction of the sediments which were formed during the early 

 periods of the Siluric and during preceding periods. This would 

 account for the presence of limestone beds in deposits formed in a 

 lifeless sea. All these limestones were more or less mixed with 

 clayey sediments; they may in fact be regarded as consolidated ar- 

 gillo-calcareous muds derived from older limestones and shales. 

 This is the character of the Waterlime and Manlius limestone which 

 succeed the Salina beds, and which, though fossiliferous, could have 

 no other source of origin than preexisting limestone beds. 



The Waterlime has been regarded as a fresh-water formation. It 

 is more likely however that it represents a return of marine condi- 

 tions through the opening of channels between this interior basin 

 and the ocean at large. This is indicated by the fauna, which in- 

 cludes undoubted marine forms. Whether this connection was 

 through the old northern channel, or whether a new channel toward 

 the east was opened is not apparent. The former is indicated by the 

 character of the Manlius limestone which succeeds the Waterlime, 

 and which in the Niagara region has features associating it with 

 the corresponding deposits of Ohio, Michigan and Ontario, rather 

 than its eastern equivalents. Whatever the nature of the transgres- 

 sion of the sea which took place in the late Siluric, it was not of 

 long duration. The epoch of the Manlius limestone and with it 

 the Siluric era were brought to a close with the withdrawal of all 

 the waters from this portion of the continent, which thereafter for 



