Exotic Terranes in the Central-Southern Appalachian Orogen and Correlations With West Africa

Abstract

Central and southern segments of the Appalachian orogen have long been subdivided into several northeast-trending lithotectonic “belts” (Fig. 1) on the basis of contrasts in lithologic character, metamorphic grade, and/or structural style (e.g. King 1955; Hatcher 1972,1978b, 1987; Rankin 1975; Glover et al. 1983). The nomenclature and regional configuration of these belts as well as the character of intervening boundaries has changed markedly over the last 30 years (e.g. King 1955; Overstreet and Bell 1965a, b; Hatcher 1972, 1978b, 1987; Butler 1980). Such subdivision of the orogen has become increasingly more difficult to reconcile with results of recent detailed geologic mapping where, for example, protolith sequences within a low-grade belt may be traced directly into an adjacent high-grade belt (e. g. Overstreet and Bell 1965b; Griffin 1972; Secor et al. 1986a). In addition, contrasting times of regional metamorphism have been documented within different areas of the same belt (e. g. Dallmeyer et al. 1986; Noel et al. 1988). These and other similarly contradictory relationships have led to the suggestion by some workers (e. g. Zen 1981; Williams and Hatcher 1982, 1983; Secor et al. 1986b; Higgins et al. 1986, 1988; Noel et al. 1988; Dallmeyer 1986, 1989a; Horton et al. 1989, 1991) that the central-southern Appalachian orogen is comprised of several markedly different, fault-bounded structural units (Fig. 2) with tectonic significance similar to that of tectonostratigraphic terranes defined within Mesozoic-Cenozoic orogens of the Circum-Pacific realm (e.g. Coney et al. 1980; Jones et al. 1983a, b; Howell and Jones 1984).