452 B. K. EMEESOK — ON THE TRIASSIC OF MASSACHUSETTS. 



fruitful discussions of Professor Davis concerning monoclinal faulting in the 

 adjoining region in Connecticut; and as I had gained all the information I 

 could from the trap sheets and the tufa bed (the only persistent and easily 

 traced members of the series), I determined to attack the problem from an- 

 other side, and, for the time disregarding dip and strike, to map the area, 

 making such lithological distinctions as my previous knowledge indicated as 

 most promising, especially in respect to persistence and distinguishability in 

 the field. 



Lithological Distinctions. — In carrying out my plan of work I chose six 

 distinctions, to which I have given names, as follows: 



1. The Sugarloaf arkose, or the felspathic sandstone and conglomerate ; 



2. The Mount Toby conglomerate, or the coarse schist and quartzite con- 



glomerate ; 



3. The Longmeadow brownstone, or the fucoidal sandstone ; 



4. The Chicopee shale, or the calcareous red shale ; 



5. The Granby tufa, or the diabase tufa ; 



6. The Holyoke and Deerfield diabase beds. 



The third and fourth of these distinctions proved less important than the 

 others, and they are merged on the map. 



Structural Relations. — The Triassic basin is a " graben " — a fault-bounded 

 block sunk, at least in places, more than three thousand feet below sea-level, 

 and more than four thousand feet below the plateaus on either side, with the 

 newest pre-Triassic rocks of the region in its bottom. 



On the western bordering plateau, measuring from the southern line of 

 the state, coarse muscovitic granites are largely developed half across the 

 state, and these are followed by coarse dark mica-schists, dark phyllites and 

 the Bernardston series of Devonian quartzites, and mica and hornblende 

 schists, in order as one proceeds to the Vermont line. 



Currents indicated by the Deposits. 



The Arkose. — Beginning at the southwestern corner of the Triassic basin, 

 strong northward-moving currents have spread the coarse felspathic and 

 muscovitic material, rudely comminuted and sorted and little rounded (quite 

 coarsely conglomeratic near the shore, and still a very coarse sandstone 

 several miles from shore), all along against the granites in the southern 

 half the state, from which this material was derived, and have carried the 

 same northward for twenty miles, past the shores of dark schists, quartzites 

 and phyllites, and at the very northern apex, in the village of Bernardston, 

 the crumbling arkose bleaches white from the abundance of the half-kaolin- 

 ized feldspar. The arkose is in great mass ; artesian wells 700 to 3,000 feet 

 deep fail to reach its bottom. 



