BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 8, PP. 197-212, PL. 16 MARCH 5, 1897 



UNCONFORMITIES OF MARTHAS VINEYARD AND OF BLOCK 



ISLAND* 



BY J. B. WOODWORTH 



(Read before the Society December 30, 1896) 

 CONTENTS 



Page 



Introduction 198 



Gay Head section on Marthas Vineyard 198 



Gay Head cliffs 198 



Non-marine plant-bearing beds 199 



Unconformity inferred between non-marine beds and marine Cretaceous. 199 



Marine Upper Cretaceous 200 



Miocene 200 



Thickness, extent, and divisions 200 



Osseous conglomerate 20 L 



Unconformity of Miocene osseous conglomerate and underlying strata . 202 



Foraminiferal or greensand bed 202 



Unconformity between Miocene greensand and osseous conglomerate. 202 



Pliocene 203 



Unconformity inferred between the Pliocene and Miocene greensand bed. 204 



Pleistocene 204 



Comparison with older beds 204 



Lower boulder bed 205 



Compound gravels and sands of the Sankaty epoch 206 



Unconformity following the Gay Head diastrophe 207 



Tisbury beds 207 



Moraine of Marthas Vineyard and Block island 207 



Unconformity between last glacial moraine and all older beds on the 



island 208 



Extension of the unconformities to Block island 209 



Availability of unconformities in determining horizons 209 



Clay Head section 209 



Cretaceous 209 



Tertiary wanting at Clay Head 210 



Pleistocene 210 



Gay Head diastrophe on Block island 210 



Mohegan Bluff beds the equivalent of the Tisbury 211 



* Published with the permission of the Director of the U. S. Geological Survey. 

 XXIX— Bull. Geol. Soc. Am., Vol. 8, 1896 (197) 



