VOLUME XXIV NUMBER 2 



THE 



JOURNAL OF GEOLOGY 



FEBRUARY-MARCH 1916 



THE ACADIAN TRIASSIC 



SIDNEY POWERS 

 Troy, New York 



PART II 



Gerrish Mountain. — Gerrish Mountain consists of a basalt flow 

 capping Triassic sandstones (Figs. 20, 22). The sandstones on the 

 west side of the mountain are horizontal, those on the east side 

 dip northward at angles of 15 or less. 



Opposite Moose Island is a cross-section of the basalt flow 

 (Fig. 22). showing sandstone faulted against agglomerate on the 

 west, with the agglomerate overlain by sandstone in one exposure; 

 a columnar basalt dike east of the agglomerate, and probably 

 separated from it by a fault; and red sandstone, east of the dike, 

 overlain by a 3-foot bed of ash, above which is columnar basalt. 

 The dike is 50 feet thick. It extends northward for some distance, 

 but it is cut off on the south by a fault between the mainland and 

 Moose Island. In either the dike, or the basalt flow, magnetite 

 has been mined near Lower Economy. 



The final exposure of Triassic basalt on the east, which may 

 originally have been connected with that at Gerrish Mountain, is 

 at Portapique Mountain, 12 miles distant, and north of Birch Hill 

 (see Fig. 23). 



Gerrish Mountain-Truro. — The broad lowland underlain by 

 Triassic strata east of Gerrish Mountain is interrupted by a long 

 Vol. XXIV, No. 2 105 



