476 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



waterfall where it crosses the road at J. Miller's house. This is directly 

 ill prolongation of the ridge north of the river, and there is no indication of 

 any fault between these points. The bed is then lacking for 2 miles south 

 because of the throw of the State-line fault, ^ but reappears again at the 

 house of A. Flower, and then follows the road closely S. 10° W. to the 

 State line and on across Suffield in Connecticut. It rises as a low ridge 

 above the sands, which conceal the contacts. The greatest thickness exposed 

 was 62 feet. 



THE TALCOTT SHEET. 



This is the anterior sheet of Percival. It enters the Granville quad- 

 rangle at its southeast corner, in the town of Suffield, Connecticut, and 

 therefore appears on the map, but it does not cross the State line. 



THE TUFF AND TUFFACEOUS AGGLOMERATES. 



THE DEERFIELD BED. 



At the first outcrop on the Greenfield-Turners Falls road the rock is a 

 complete "schalstein," a thin-bedded, dark -green rock, largely decomposed 

 into a flaky chlorite, and abounding in grains of calcite and a reddish 

 zeolite for the most part iron-stained prehnite. This bed seem to rest 

 directly upon the trap and to have but limited extent. 



THE GRAN15Y BED. 



The coarse arkose or sandstones, consisting of slightly waterwoni and 

 sorted granitic materials, wliicli dip beneath the great bed of diabase of the 

 Holyoke range, are followed above the diabase by exactly similar beds of 

 pale-bufl" arkose containing little iron and having a low dip south from the 

 Mount Holyoke range and southeast to east from the Mount Tom range. 



This is followed by heavy beds of black tuff" and tuff"aceous sandstone, 

 which vary from fine-grained volcanic sandstones to coarse breccias and 

 agglomerates, and from rocks made up wholly of volcanic debris to such as 

 contain fragments of granitic and gneissoid rocks, or in the finer-grained 

 varieties contain the materials of granite, especially white mica on the 

 lamination faces and gTains of quartz in the maj-s of the rock. In other 

 cases rounded masses of diabase ai"e distantly scattered in deep-red sandstone- 



This band begins opposite the east end of the diabase bed and half a 

 mile south of it, and, attaining a surface width of 1,600 feet, runs west 



1 See pp. 370, 450. 



