Appalachian Structural Style in Southern New Brunswick

Abstract

The strain geometry of southern New Brunswick can be analyzed in terms of four major structural sub-divisions, which mark a variation in style from tilting and translation of rigid strata, single-phase cylindrical folding by flexural slip, polyphase folding by flexural flow, to extreme cataclastic flow with attendant transposition of early planar fabrics. Shallow dips of planar elements and shallow plunges of hinge lines occur in distinct zones, Maximum strain occurred along the northeast-trending Lubec-Belleisle zone, where vertical attitudes of planar and linear elements prevail. Cataclastic fabrics are regionally developed together with narrow mylonitic zones.Rock heterogeneity in part influences structural style, with early granitic plutons tending to act as rigid buttresses, but the major sub-divisions are not controlled by lithologic boundaries. The structural sub-divisions transgress the present position of fault boundaries.Southern New Brunswick is probably a relict continental margin. If regional folding, cataclasis, and later faulting can be attributed to the closing of the Proto-Atlantic seaway in Middle Devonian to Carboniferous times, the localization of intense strain in southern New Brunswick and particularly along the Lubec-Belleisle zone may be accounted for by assuming that stress concentrations would occur in the region of the shelf slope margin.