Abstract

Late Carboniferous sedimentation and penecontemporaneous deformation in the Fundy coastal zone of southern New Brunswick occurred in response to dextral transpression on faults that now flank the northwest margin of the Fundy Basin. Both reflect the development of a basement-involved, fold-thrust belt, the position of which coincides with a major, right-lateral compressive bend in the Upper Carboniferous Cobequid-Chedabucto Fault System. Relationships are similar to those of the San Andreas Fault within the major restraining bend of the Transverse Ranges.

Syntectonic, Westphalian deposition of the Balls Lake and Tynemouth Creek formations records the development of alluvial fans that prograded northwestward into basins drained by the major, northeast-flowing fluvial systems of the Lancaster and Boss Point formations, in response to the uplift of southeasterly source areas. Regional structures developed in response to sustained northwest-southeast shortening, and trend perpendicular to the compressional component of shear. Initial deformation produced northwest-directed thrusts and major, northwest-vergent overturned folds that structurally invert local stratigraphy. Associated penetrative fabrics dip broadly southeast but commonly steepen and intensify along the Fundy shore, where overthrusting accompanied local mylonitization and greenschist facies metamorphism on right-stepping, high-angle fault zones. Interpreted as en echelon, convergent wrench strands synthetic to a listric, offshore extension of the Cobequid-Chedabucto Fault System, these faults shallow into thrusts to form positive flower structures. Continued compression accompanied renewed thrusting and backthrusting and produced coaxial fold trains and penetrative second fabrics that verge both northwest and southeast. Subsequent extensional reactivation of selected thrusts reflects the negative inversion that accompanied Triassic development of the Fundy Basin.