THE ROXBURY CONGLOMERATE SERIES. dl 
contortions, together with all the other similarities of the Squantum and Woods- 
ville deposits, would appear to be conclusive evidence of the similar origin of the 
two deposits. . 
The slate under the tillite, of the Dorchester member of the Roxbury forma- 
tion at Squantum, shows regular fine and coarse components, in specimens taken 
about twenty-five feet below the tillite. The sediment is coarser, in most of 
this slate near the bottom of the tillite, than in the slate above the tillite. This 
fact probably explains the lack of regular intervals in the banding, which has 
been observed in a number of the microscopic sections. The currents were so 
swift that the fine material was not allowed to remain as deposited. Evidence 
of this is found in some layers of the fine material which have been penetrated 
by the coarse sediment, the latter lying in pockets in the upper part of the fine 
layer. Other evidence of this current action is found in small fragments of 
layers of fine material which has been swept up and included in the coarse 
material. 
This lower slate was greatly contorted by over-riding ice. Only a few 
specimens have been found which are free of contortions. The contortions 
may be found as low as fifty or sixty feet below the tillite. About this horizon 
the sediment of the banding is much finer than near the tillite and as fine as any 
sediment found in the slate above the tillite, and shows, under the microscope, 
regular banding. (See p. 41). 
At Crow Point the slate in Huit’s Cove shows regular banding in micro- 
scopic sections, and also without the aid of the microscope in alternating slaty 
and sandy layers. Near the deposit believed to be tillite (Sayles, 1914, p. 159) 
the slate shows no good banding to the naked eye, but with the microscope 
regular banding of fine and coarse components shows very well. The sediment 
is extremely fine and would seem to indicate quiet and possibly deep water. 
It is probable therefore, that this tillite is sublacustrine in origin. If it is not, 
the chances are that this slate lies under the tillite. The attitude of the speci- 
mens from which the microscopic sections were made was not marked, so further 
sections must be made to determine the position of the formation. As noted 
above (p. 48), it is invariably true that the finest part of the fine components 
ison top. (See Plate 16, fig. 2). 
On the point which forms the northern part of Huit’s Cove occur some alter- 
- nating sand and slate layers. Regular banding of similar nature may be found 
along the shore to the north. 
The slate at Brighton is banded and the bands show regular intervals 
