BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 8, PP. 59-86, PLS. 3-9 FEBRUARY 13, 1897 



DIABASE PITCHSTONE AND MUD ENCLOSURES OF THE 

 TRIASSIC TRAP OF NEW ENGLAND * 



BY B. K. EMERSON 



(Presented before the Society August 22, 1896) 

 CONTENTS 



Page 



Granby tuff 59 



White diabase tuff 60 



Mud enclosures 61 



General character of the surface material 61 



The underrolled material 62 



Origin of the deposits 63 



Diabase pitchstone and mud enclosure 64 



Origin of the pitchstone 64 



General character 65 



Greenfield quarry exposures and contacts , 65 



Meriden " ash bed " 66 



Eruption of glass breccia through trap sheet 67 



Petrographical descriptions 69 



Surface of beds at Dibbles crossing and Larabee's quarry 69 



Base of Holyoke bed 69 



Greenfield bed 70 



Glass breccia 70 



Amygdaloidal sandstone , 71 



Contact material 72 



Lithophysae 72 



Meriden " ash bed " 72 



Basal bed 72 



Hyalopilitic diabase 72 



Diabase pitchstone 73 



Glass and sand 75 



Meriden mud volcano 76 



Chemical discussion -. 77 



Origin of the glasses and minerals 78 



Resume 79 



Explanation of plates , 80 



Granby Tuff. 



A bed of tuff is composed of fragments of volcanic rock more or less 

 sorted and transported by the action of water and whose fragments, 



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

 I3&— Bull. Geol. Soc. Am., Vol. 8, 1896 (59) 



