12 GREEN MOUNTAINS TN MASSACHUSETTS. 



in connection with the mixture of dike material and sand, and the stopping 

 of the dike at the quartzite, prove sufficiently the pre-Cambrian age of the 

 granitoid gneiss. And this is emphasized by the fact that both the quart- 

 zite and white gneiss are frequently conglomerates. 



The structural conformability of which I have spoken above is due 

 simply to the generally parallel lamination that has been forced upon the 

 rocks of the region by the folding. 



We had now established the fact that in this part of the Green mountains 

 the column in the main range consists of a Lower ( lambrian quartzite-con- 

 <domerate-white-gneiss formation, resting with a time break upon a coarse 

 granitoid gneiss, and conformably overlain by a great thickness of schists. 



Parallel with the study of Hoosac mountain, that of Greylock was carried 

 on by Mr. T. Nelson Dale, assisted, for a time, by Mr. W. H. Hobbs. This 

 mass was shown to consist of a great lower crystalline limestone, overlain 

 by a heavy mass of schists, above which another thick mass of limestone 

 was overlain by still another great mass of schist, the whole column contain- 

 ing about 2,000 feet of limestone, and 2,500 to 4,000 feet of schist. These 

 estimates are based on measurements of areas that have been subjected 

 to lateral pressure, and of course do not claim to represent the original 

 thickness. 



Lower Silurian fossils have been found in the continuation of a part of 

 the lower limestone in Vermont. Mr. Dale found the Greylock limestone 

 and schists conformable throughout and exhibiting vertical transitions. 



It seemed almost impossible to find points where the actual stratigraphic 

 relation of the limestone to the quartzite could be observed, but I was for- 

 tunate in finding such a place on Lachines creek, near Berkshire station. 

 Later, by means of digging, which was done here under Mr. Putnam, it was 

 shown not only that the quartzite and limestone are structurally conform- 

 able, but that thev are bound together by vertical transition through calca- 

 reous flaggy quartzites. We have here in an overturned fold, with easterly 

 dip, tlie Stockbridge limestone dipping under the older Cambrian quartzite 

 formation. The limestone proper is succeeded toward the quartzite by 

 flaggy quartz schists, and these by a heavy development of schistose calca- 

 reous quartzite. East of this the quartzite becomes friable, and has here 



