Structural Evolution of the Mulberry Recess Eastern Blue Ridge-Talladega

The Mulberry Rock recess exposes four different lithotectonic metamorphic units; these lithotectonic units were metamorphosed before the thrusting that occurred due to the Alleghanian orogeny. The lithotectonic units were divided into 1. allochthonous assemblages consist of two stratigraphic sequences: 1. the Talladega slate belt and 2. the Hillabee Greenstone and 2. parautochthonous assemblages consist of three units: 1. the Wedowee Formation (New Georgia Group, the northeastern extension in Georgia) 2. the Emucfaw Group, and 3. the Dahlonega Gold Belt. The allochthonous assemblages were deposited in extensional basins formed along the eastern Laurentian plate’s outermost passive margin. In contrast, the parautochthonous assemblages consist of predominantly deep-water immature metasedimentary units beside bimodal volcanic rocks formed in a supra subduction system built on adjacent late Neoproterozoic early Paleozoic rocks of the passive Laurentian margin at the trailing edge of the Iapetus ocean, specifically in a continental margin back-arc setting. The Hillabee Greenstone metavolcanic unit shows a bimodal volcanic suite comprising of two distinct lithologies: one composed of metadacite that was crystallized at 470 ±3 Ma and the other composed of metabasalt formed in an island arc basalt environment for the felsic unit. The Pumpkinvine Creek Formation rocks samples are characterized as metavolcanic (basalt) formed in a tholeiitic environment and metafelsic (rhyolite and/or dacite) formed in a calc-alkaline environment. The Mulberry Rock Gneiss was formed by anatectic melting of older Grenville-aged rocks. The Wedowee-Emuckfaw-Dahlonega basin comprises two units metabasaltic rocks and metasedimentary rocks formed in a supra subduction zone environment. Stereographic analysis of the orientational data inside and outside the Mulberry Rock recess shows that all units generally strike northeast and dip northwest. Isoclinal antiformal and synformal regional folds are the dominant structures in the mapping area. Cross-sections across the Mulberry Rock recess were drawn to scale and show no vertical exaggeration. The cross-sections show that the overthrust sheets vary in thickness and dip gently in all directions around the Mulberry Rock recess and reveal that the Mulberry rock antiform is an upright open fold that broadly arches the overriding thrust sheets. Moreover, the cross-sections also show that the Allatoona fault follows the geometry of an out-of-sequence thrust fault. Furthermore, the Mulberry Rock Gneiss’s structural xi position might suggest that it was a laccolith-size intrusion reduced in size by faulting. The crosssections reveal that the Allatoona fault cuts down section in its footwall and became the base of the Pumpkinvine Creek and Canton Formations thrust sheet on top of the Talladega slate belt thrust sheets in the western part of the recess. Many tectonic settings could collaborate in the buried basement to generate differential movement and uplift the antiform. The fact that the Mulberry Rock antiform is doubly plunging is one evidence of across folding events.