BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 10, pp. 199-244, PLS. 22-28 APRIL 6, 1899 



PRE-CAMBRIAN FOSSILIFEROUS FORMATIONS 



BY CHARLES D. WAI.COTT 



(Read before the Society December 30, 189S) 



CONTENTS 



Page 



Introduction ■ 200 



Geological notes. 201 



Belt terrane 201 



Literature of the subject 201 



Author's investigations 203 



Neihart quartzite and sandstone . 204 



Chamberlain shales 206 



Newland limestone 206 



Grayson shales 206 



Spokane shales 207 



. Empire shales 207 



Helena limestone , 207 



Mai-sh shales. . ... ., ' 207 



Section of the Belt terrane 208 



Age of Cambrian beds resting on Belt terrane , 209 



Unconformity between Belt terrane and Cambrian 210 



Extent and character of recognized contacts 210 



Explanation of apparent conformity 213 



Extent of unconformity 213 



Grand Canyon terranes 215 



Composition and character 215 



Chuar terrane 215 



TJnkar terrane 216 



Age of Cambrian beds resting on Grand Canyon series ; 217 



Unconformity between Grand Canyon series and Cambrian 217 



Location of the contact 217 



Extent of unconformit}' 218 



Llano series of Texas. . . 218 



Avalon terrane 218 



The formations in general 218 



Signal Hill sandstone 219 



Momable slates 219 



Torbay slates 219 



Conception slates 220 



Age of Cambrian beds resting on Avalon terrane 220 



XXX— Bur.r. Gr.or,. Soc. Am., Vol. 10, 1808 (199) 



