P-T paths from northwestern New Hampshire: metamorphic evidence for stacking in a thrust/nappe complex

Abstract

Petrologic study of polydeformed metasediments on the western flank of the Bronson Hill anticlinorium in northwestern New Hampshire demonstrates that two adjacent structures were metamorphosed under different baric conditions during the Acadian orogeny. The Salmon Hole Brook syncline experienced loading with limited heating during metamorphism. In contrast, rocks of the proposed Piermont allochthon located southwest of the Salmon Hole Brook syncline experienced syntectonic metamorphism at pressures between 5 and 7 kb, culminating in a trend of heating with decreasing pressure of approx. 0.5 kb. The rocks of these two regions were juxtaposed during the westward transport of a thrust/nappe complex, such as has been described for western and southwestern New Hampshire and north-central Massachusetts. -from Authors