25-4 Unearthing New Constraints for the Polyphase Evolution of the Brevard Fault Zone, North Carolina: Insights from New Exposures in the Aftermath of Helene

Session: New Research in the Appalachian-Ouachita Orogen: Integrated studies from the Foreland to the Hinterland (Posters)

Presenting Author:

Authors:

Abstract:

The dextral transpressional Brevard fault zone (BFZ) represents perhaps the most prominent structure in the southern Appalachians, and as such, it has been invoked in a wide range of models for the complex assembly of this composite orogenic system. Despite this, significant gaps exist in our understanding of the precise timing of slip (including intervals of reactivation) and the rheologic behavior of the BFZ during multiple Paleozoic orogenic events. Unraveling this polydeformational and polymetamorphic evolution of the BFZ remains a priority for the southern Appalachian tectonics community. In September 2024, the remnants of Hurricane Helene produced catastrophic flooding and widespread landslides and debris flows across the southern Appalachian Blue Ridge. These events drove significant erosion and created new exposures particularly along the Blue Ridge escarpment, which coincides in many places with the BFZ. One exposure in Fairview, NC exposes a structural thickness of ~700 m into the BFZ mylonitizied footwall, of which ~70% is exposed bedrock, providing a somewhat singular opportunity to examine BFZ motion history and rheology. Here, we employ detailed field mapping, sampling transects, petrographic, SEM, and microprobe thin section analysis, as well as monazite, apatite, and titanite laser ablation split stream U-Pb dates, to unravel the complex polymetamorphic and polydeformational history of the BFZ in western North Carolina.  

The BFZ footwall here is primarily composed of Alligator Back and Ashe metagraywacke and graphitic schist, up to peak sillimanite grade, however, most of the section is retrograded to greenschist. This work will focus on identification of mineral phases for dating (e.g., monazite, apatite, titanite, xenotime) and linking those mineral phases to the structural and thermal evolution of the BFZ through deformation temperature indicators (e.g., quartz recrystallization mechanisms) and metamorphic assemblages. We will be using laser ablation split stream with accessory phase geochronology to tie trace element chemistry to pro- and retrograde phases in the assembly. These results should be relevant for elucidating the complex metamorphic and strain motion history of the BFZ. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.