THE GRANBY TUFF BED. 477 



parallel to the diahase to and across the Connecticut, and continues south 

 ])arallel to the Mount Toua range to within a short distance of the Holvoke 

 town line. 



It appears first in the bluff overlooking the northern of the Belcher- 

 town ponds as a thin-bedded, rusty sandstone with grains of diabase. It 

 strikes N. (iO° W. and dips west into the hill and l)eueath the samlstone, 

 and has plainly been faulted into its present position, and received thus 

 its unusual westward dip. It is wholly separated from the remainder of 

 the bed. 



Farther west, where the Bay road after crossing the diabase goes south 

 toward Belchertowu, the tuff does not outcrop, but in the fields west of this 

 road abundant fragments occur by which it can be approximately traced, 

 and soon it appears in a strong ridge which can be followed west to the next 

 road. Here the tuff' appears for a long distance noi-th and south of the second 

 house met after going south across the mountain into Granby (the house 

 formei'ly occupied by A. Convere, now in ruins), and tracing it west it runs 

 just south of a small diabase mass southwest of this house. It is an arkose 

 containing in great immber angular diabase fragments, some as large as a 

 pea, and is cut off by a fault, which can be traced very cleai'ly in the woods 

 south of the diabase. Farther west it has been crossed at several points but 

 not followed continuously through the densely wooded area to the next road, 

 i. e., the main or Notch road, and it appears at the first branching of this 

 road south of The Notch. The rounded rusty hummocks of the tuft" are 

 very conspicuous. 



The rock is composed mainly of trap in small angular fragments which 

 look like pitchstone and which consist of a diabase with semicrystalline base. 



The tuft" bed makes a small angle with the road running east from this 

 point, and its exposures are found abundantly in the roadside until the road 

 goes down onto the terrace sands. The outcrops of the tuff vary from deep- 

 brown, thin-bedded sandstones, which the microscope shows to be quartz 

 sandstones impregnated with the finest dust of the trap, to agglomerates 

 in which masses of trap a foot across appear, as in the woods just south of 

 where the ninth volcanic core (see p. 483) crosses the road. 



Farther east the tuff bed is cut off completely by the ninth core. The 

 best exposures are where the bed is crossed by the wood road which runs 

 north from Moody Corners, where the ru.sty tuff weathers into a pile of 



