FIELD RELATIONSHIPS AND GEOCHRONOLOGICAL DATA: IMPLICATIONS FOR 3-D MODEL RESULTS OF NEOPROTEROZOIC DEPOSITION AND THE PALEOZOIC STRUCTURAL EVOLUTION OF THE WESTERN BLUE RIDGE, SOUTHERN APPALACHIANS

The southern Appalachian western Blue Ridge (WBR) is composed of numerous northwest-directed early to late Paleozoic thrust sheets, which reveal pronounced variation in stratigraphic/structural architecture and timing of observed deformation and metamorphism. Historically, unraveling stratigraphic, structural, and temporal relationships of this terrane has proved problematic. New 2-D and 3-D models of the WBR from northeast TN to Cartersville, GA, which are constrained by both observed field relationships and geochronological data, allow visualization of present-day deformed state architecture and affords the opportunity to systematically retrodeform various model components.

Major Mesoproterozoic to late Paleozoic WBR events include: 1) igneous crystallization of WBR basement during the Mesoproterozoic (1200-1000 Ma), 2) deposition of Ocoee and other “rift” related sequences during the Neoproterozoic (900-700 Ma), 3) pronounced thermal event during the latest Neoproterozoic (700-550 Ma), 4) deposition of Chilhowee and other “drift” related sequences, 5) Ordovician thermal-deformational event (Taconic orogeny; 470-440 Ma), 6) Devonian thermal event with associated fault reactivation (Neoacadian? orogeny; 370-350 Ma), 7) Mississippian-Pennsylvanian thermal-deformational event (Alleghanian orogeny; 330-280 Ma). In order to produce the most meaningful and accurate interpretations of tectonic evolution, all available constraints must be integrated into 3-D structural architecture models during retrodeformation. If done properly, much insight may be gained for understanding the evolution of polydeformed terranes such as the WBR.