GEOLOGY OF OLD HAMPSHIRE COUNTY. 5 



Upon reassembling at 2.15 o'clock p. m. the following paper, descriptive 

 of the geology of the locality, was read : 



GEOLOGY OF OLD HAMPSHIRE COUNTY, IN MASSACHUSETTS 

 BY B. K. EMERSON 



\_ Abstract'] 



Contents 



Page 



The area discussed 5 



The crystalline rocks 5 



The Trias 6 



The Quaternary deposits 6 



The Area discussed 



Old Hampshire county includes Franklin, Hampshire and Hampden counties, 

 and Springfield is in the center of the latter. 



The Crystalline Rocks 



On the western border of the Green Mountain area as it crosses Massachusetts 

 and overlooking the Housatonic valley is a series of pre-Cambrian outcrops, which 

 are the oldest rocks of the state and the substratum on which the others rest. 

 They consist of coarse gneisses, especially characterized by blue quartz and allanite, 

 coarse porphyritic structure and stretching, and by great beds of highly crystalline 

 limestone, with chondrodite, coccolite, titanite, phlogopite and wernerite. 



The most important of these beds are the Hoosac, the Hinsdale and the Tyring- 

 ham areas, and the limestone beds connected with the two latter have caused the 

 two most important passes through the range — the Westfield and the East Lee- 

 Farmington valley. 



On the pre-Cambrian rocks rest the Becket conglomerate gneisses of Cambrian 

 age, and above them a great series of sericite schists (the Hoosac schists, Eowe 

 schists, Chester amphibolite and Hawley schists), which are about cotemporaneous 

 with the Stockbridge limestone of the Housatonic valley. 



The Chester amphibolite series, containing many serpentine beds and the cele- 

 brated Chester magnetite-emery bed, divides this series into two members, and the 

 highly ferruginous Hawley schists cap the series in the northern part of the state. 



A considerable unconformity separates the next series — the calciferous mica- 

 schists of Hitchcock (the Goshen and Conway schists) — from the sericite-schists. 

 These are dark biotite-spangled garnet-schists, which are probably Upper Silurian. 

 They are greatly cut by large granite masses and graduate upward into the Leyden 

 argillites. Upon these rest unconformably the Upper Devonian Bernardston series 

 of highly crystalline amphibolites, mica-schists and fossiliferous quartzites and 

 limestones. 



Crossing from the Housatonic to the Connecticut, one passes from a region of 

 rocks which have been folded under a heavy load without faulting to an area 

 which has been deformed under an inadequate load, and which is faulted into 

 great blocks and greatly cut by granites. 



