COLLABORATIVE RESEARCH: Taconic vs. Acadian Tectonothermal Record in the Blue Ridge: Rb-Sr and 40 Ar/39 Ar Mineral Age Constraints

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Recent discoveries of Silurian/early Devonian fossils in metamorphosed clastic rocks of the western Blue Ridge province, southern Appalachians have called into question the prevailing views of Blue Ridge tectonic evolution. The fossiliferous rocks indicate that metamorphism must be Devonian or younger, whereas a number of published radiometric ages indicate Ordovician metamorphism. This study will resolve the extent and role of Taconic (Ordovician) versus Acadian (Devonian) metamorphism and thus the discrepancies between the paleontologic and radiometric data. 40Ar/39Ar and Rb/Sr geochronology will be used in two well- studied areas to constrain the timing of metamorphism, mylonitization and thrusting. The results of this study will resolve the current controversy surrounding the tectonic evolution of the Blue Ridge crystalline rocks of the southern Appalachians.