372 E. O. Rovey—Trap Ridges of the 



South of the north end of Pond Rock and east of the Bran- 

 ford-Foxon road, between the main ridge and the first eastern 

 range, much, coarse, hard, yellowish-brown to red sandstone 

 occurs together with some layers of shaly and soft stone. 

 Overlying this and at least a third of a mile from the rock, we 

 come upon a peculiar conglomerate containing bowlders and 

 fragments of trap, which will be described later. It is briefly 

 noticed by Percival,* who does not seem to have attached 

 much significance to it. I have not found any bowlders or 

 fragments of trap in the sandstone immediately overlying the 

 trap of the main ridge or in the area just referred to between 

 the coarse conglomerate and the main ridge. 



Sandstone and sandy shale are exposed at several places, and 

 to a considerable extent on the east side of Lake Saltonstall. 

 For a third of a mile, beginning just east of the lake, the rail- 

 road cuts through two low hills which are composed of shale 

 with an occasional stratum of sandstone. There is some varia- 

 tion of strike and dip in these cuts, but most of the strata of 

 the western cut strike N. 10° E , while in the eastern the gen- 

 eral strike is N. 20° E. The dip decreases from 61° E. near 

 the lake, to 42° E. in the eastern part of the eastern cut. This 

 shale is the continuation of that at the northern end of the 

 second member of the main range which dips 75° E. Half 

 way up the lake the eastern bank for several hundred yards is 

 formed by a low bluff of sandy shale having its strike N. 52° E. 

 and its dip 30° E. The lake is a fourth of a mile wide at this 

 point. Within a quarter of a mile of the head of the lake 

 coarse, rather hard sandstone is exposed at the water's edge 

 under overhanging trees. The strike of the rock is N. 12° E., 

 its dip 27° E. The trap is an eighth of a mile distant. Ref- 

 erence to the map will show that the strikes of these exposures 

 of sandstone are nearly parallel to the trend of the heavy trap 

 ridge across the lake from them. 



Overlying sandstone is exposed at but few places near the 

 first eastern range, and actual contact is shown at but one 

 place : it is where the Branford Foxon road crosses the ridge 

 (near I, on the map). At this place a thin layer of very hard 

 sandstone is firmly welded to the trap, which is vesicular. The 

 strike of the strata is generally parallel with the trend of the 

 range and the dip is high and away from the trap. 



One contact of the trap of the second eastern range with the 

 sandstone on its eastern side has been observed ; this is at and 

 near where the road from Bran ford village to "Cherry Hill" 

 crosses the ridge. The locality is> marked B on the map. 

 Fig. 5 was made from a photograph of the contact exposed by 

 the west side of the road. The strike of the sandstone is 



* Geo!. Conn., p. 324. 



