The Trap System. 



529 



during the time when the upper beds of the sandstone were deposit- 

 ing. Were it not for the occurrence of a trap conglomerate on the 

 upper side of the greenstone, we might allow that the greenstone was 

 protruded at the same time when the sandstone was elevated, or sub- 

 sequent to that epoch. This circumstance proves that the higher 

 beds of sandstone, or at least a part of them, w r ere deposited subse- 

 quent to the elevation of the greenstone : otherwise, how could round- 

 ed masses of the greenstone be found in the conglomerated sandstone. 

 But in several places, as at Turner's Falls, and on the southeast side 

 of mount Holyoke, these higher strata of sandstone are much more 

 tilted up than those beneath the greenstone: which seems to indicate 

 that this latter rock forced its way through the sandstone after the de- 

 position of the upper beds. These facts I confess are difficult to be 

 reconciled : But they prove I think, that the greenstone was eleva- 

 at a period (more probably at more than one period,) different from 

 that when the sandstone was thrown up. 



The prevailing easterly dip of the sandstone containing these 

 ridges of greenstone could not have been the result of the protrusion 

 of the latter rock : for the beds below the greenstone, are, for the 

 most part, quite as much inclined as those above it. This proves that 

 some other agency must have raised the sandstone ; except in those 

 few cases alluded to above, where the greenstone seems to have in- 

 creased the inclination of the strata. Hence only the sandstone in 

 these limited spots can be regarded as belonging to this system of ele- 

 vation ; and it embraces only the trap ranges extending from New 

 Haven to Vermont. These, as may be seen on Plate XV, run in 

 general a few degrees east of north. 



I have in another place noticed a limited deposit of new red sand- 

 stone and greenstone in Woodbury and Southbury Ct. This forma- 

 tion resembles exceedingly the analagous sandstone and greenstone 

 in the valley of the Connecticut. The direction of the ridges of 

 greenstone in the Woodbury valley corresponds very nearly, also, 

 with that of the trap in the Connecticut valley; indicating a synchro- 

 nous protrusion. I omitted in treating- of new red sandstone to no- 

 tice a similar formation, about 60 miles long and 30 broad, in New 

 Jersey ; and extending northerly into New York, at least as far as 

 the Palisadoeson the Hudson.* Prominent ridges of greenstone in- 

 tersect this formation, running from north to south, and resting on 



* Pierre jn Am. Journal of Science. Vol. 2. p. 181. 



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