376 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



He was not satisfied with these numbers, as they seemed excessive; 

 and he gives consideration to original deposition on an incline and to fault- 

 ing as explanations, and rejects both, effectively disproving the first and 

 remarking concerning the second that he had been iinable to find any con- 

 siderable faults, such as the theory would demand. Accordingly he consid- 

 ered the general easterly dip to indicate that there was a uniform progression 

 from older to newer beds in passing from west to east and made a tlu-eefold 

 division — (1) the sandstones below the trap, (2) the sandstones above the 

 trap, and (3) the conglomerates of Mount Toby, the latter being the newer. 



More favorable exposures and more detailed mapping have revealed 

 many faults, and I feel sure that many more remain concealed. 



Along the eastern side of Mount Toby the coarse conglomerate rests 

 ill normal unconformity upon the old quartzite, and instead of being newer 

 than the fine-grained sandstones (the distinctions I have made of arkose and 

 red fucoidal sandstone agree in the main, though not exactly, with the above 

 distinctions, sandstone below the trap and sandstone above the trap), it is 

 certainly older than these, and, as an eastern-shore deposit, is to be placed 

 parallel with the arkose which forms the shore deposit along the western 

 side of the estuary. ' As I have indicated elsewhere that the waters spread 

 over this portion of the basin somewhat after the time of their advent in the 

 western portion of the l^asiu, I should not j^lace them parallel to the base of 

 the arkose on the west, but rather to its middle and upper portions, and 

 should place the main continuous mass of the red sandstones and shales 

 which, beginning in South Hadley, extend broadly southward in the central 

 portion of the basin as in part later than lioth. They are largely the tidal 

 mud flats of a shoaled-up and contracted estuary which nnist have had high 

 tides like the Bay of Fundy. 



The dips are certainly for the most part easterly, but this is commonly 

 overstated. Across Hatfield they are largely westerly. In Mount Toby 

 they are nearly horizontal. East of Turners Falls and in the Holyoke 

 range they swing round to south. In Hampden County they are very low 

 and rarely observable in the eastern portion. With these dips and with the 

 repeated monoclinal faulting the boundaries, if we could draw them accu- 

 rately, would often be sharply serrate, but hindered by the uniform char- 

 acter of the rocks of the series, and more by the thick cover of till, one 

 can draw only approximate boundaries. 



