Reconstructing the tectonic evolution of the southern Appalachian metamorphic internides is hampered by the relative paucity of accurate geochronologic constraints and the apparent rarity or absence of Paleozoic cover sequences. At the orogen’s greatest width, near the junction of Georgia, North Carolina, and Tennessee, the western Blue Ridge is a composite metamorphic allochthon of three major thrust sheets: (A) a basal sheet above the Great Smoky fault overlying rocks of the foreland thrust belt composed of the Lower Cambrian Chilhowee Group and underlying Sandsuck Formation of the Neoproterozoic Walden Creek Group; (B) an intermediate sheet above the Maggies Mill–Citico fault composed of the middle Paleozoic Maggies Mill Formation; and (C) the main mass of the western Blue Ridge above the Alaculsy Valley–Miller Cove fault composed of the Neoproterozoic Ocoee Supergroup, and younger overlying sequences in the Epperson and Murphy synclinoria. The age of peak deformation and metamorphism in all of these sequences has historically been assigned to the Ordovician Taconic orogeny, but recent paleontologic discoveries suggest these events are significantly younger. In addition to the middle Paleozoic fauna recently reported from the Maggies Mill Formation in the intermediate thrust sheet, Silurian-Devonian conodonts have been found in units formerly correlated with the Walden Creek Group in the Epperson synclinorium. These discoveries suggest that widespread middle Paleozoic successor basin sequences unconformably overlie the Neoproterozoic-Cambrian drift-facies of the Chilhowee Group (and equivalents) and underlying rift-facies of the Ocoee Supergroup, and require modifications to existing models for the timing of the region’s stratigraphic framework and tectono-metamorphic evolution.

中文翻译：

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阿巴拉契亚西部蓝脊复杂中古生代构造演化的新古生物学证据

重建南阿巴拉契亚变质内陆的构造演化受到精确的地质年代学约束的相对匮乏以及古生代盖层序列的稀有或缺乏的阻碍。在造山带的最大宽度处，靠近佐治亚州，北卡罗来纳州和田纳西州的交界处，西部蓝脊是三个主要逆冲片层的复合变质异源变质层：（A）大烟断层之上的基片，覆盖前陆逆冲层的岩石由下寒武统奇豪威群和下元古界沃尔登河群的下伏的沙吸组组成的带；（B）玛吉斯米尔—奇蒂科断层之上的中层，由中古生界玛吉斯米尔组组成；（C）由新元古代Ocoee超群组成的Alaculsy Valley-Miller Cove断层上方的蓝岭西部的主要块体，以及在Epperson和Murphy斜向层中较年轻的上覆层序。从历史上看，所有这些序列的峰值变形和变质时代都已归因于奥陶纪塔康造山带，但最近的古生物学发现表明这些事件明显年轻。除了最近在Maggies Mill组中段逆冲片中报告的中古生界动物群外，在与Epperson向斜层中与Walden Creek群有关的单元中还发现了志留系-德文统牙形体。