BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 2, pp. 293-300, PL. 11 March i7, 1891 



THE CHAZY FORMATION IN THE CHAMPLAIN VALLEY. 



BY EZRA BRAINERD. 



{Read before the Society December 30, 1890.) 



CONTENTS. 



Page. 



Introduction 293 



The Detailed Sections 294 



Section at Valcour Island 294 



Chazy Section 296 



Isle La Motte Section 297 



Highgate and St. Armand Section 298 



Cornwall Section 299 



Crown Point Section 300 



Orwell Section 300 



Distribution of the Chaz}'- Formation 300 



Introduction. 



The numerous islands and promontories of Lake Champlain afford excel- 

 lent opportunities for the study of the Lower Silurian. Along its western 

 border are the steep, high hills of the Archean, apparently the former shore 

 of the old Silurian sea ; along its eastern border stretch the hills of red sand- 

 rock and dolomite of the Cambrian age, brought up by the great overthrust 

 that continues on northward to Quebec. East of this overthrust, toward 

 the Green mountains, the Lower Silurian rocks are extensively crumpled 

 and metamorphosed, and hard to decipher ; but westward through the lake 

 region they are less disturbed, retain their fossils, and present many remark- 

 ably fine exposures along the shores where the waves have washed away 

 the soil. 



The geological importance of this region was recognized by Professor 

 Emmons, who, in his New York report in 1842, named these formations the 

 Champlain group. Subsequently Professors Thompson, Adams and Hitch- 

 cock made valuable contributions to our knowledge of these strata ; but it 

 is safe to say that the work of these earlier geologists was left incomplete. 

 Many of the best exposures were difficult of access, and seem not to have been 

 visited. The details of stratigraphy were never worked out ; the thickness 



X LI V— Bull. Geol. Soc. Am., Vol. 2, 1890. (293) 



