Page:The Journal of geology (IA journalofgeology21894univers).pdf/438
exceed shearing and the development of the regional schistosity would not be expected. It is nevertheless true that the core rocks, although as a whole more massive than the border series, have in most localities a pronounced lamination not always due to the formation of micas, as in the Mendon series, but frequently the result of a rearrangement of the chemical combinations of the rock brought about by metasomatic and dynamic agencies. This is shown by the formation of amphibolites from some basic eruptive rock and by banding produced by the parallel injection of pegmatitic veins along the schistosity. If the core rocks were below the neutral zone during the folding that induced the regional clearage in the border series, then manifestly the intricate flexing of the inferior rocks was developed before the deposition of the Mendon series; if the core rocks were above the neutral belt they should have the normal lamination and characteristic folding universally occurring in the upper series, which is not the case.
A coarse granitoid gneiss and some associated quartzose sedimentaries occurring at North Sherburne are characterized by hundreds of minute faults to the square foot, having most divergent trends. That this was an area below the zone of neutral motion, thus permitting compensation by faulting or crushing is not tenable since the rocks are not more than 300 feet below a metamorphosed conglomerate, in which no faulting of this nature has taken place. In this phenomena we have more evidence pointing to the conclusion that the core rocks have undergone many mutations not participated in by the overlying Mendon series and must therefore be separated by an unconformity.
The conglomerate-gneiss horizon.—On the west side of the range, the Hitchcocks have colored in this horizon extending in scattered patches beneath the "quartz-rock" from Sunderland on the south to the Canadian boundary, thickening toward the north. A patch is shown at Sunderland and another at Wallingford. Beginning in the town of Ripton, if this interpretation be correct, it extends continuously across