A geochronological study of the Lincolnton metadacite, a prominent unit in the slate belt along the Georgia-South Carolina border, provides indicated primary ages of 554 ± 20 m.y. (Rb-Sr) and 568 m.y. (U-Pb, zircon). On the basis of both lithological and geochronological data, the Lincolnton metadacite and associated felsic pyroclastic sequence are interpreted to be correlative with the Uwharrie Formation in the Albemarle-Denton-Asheboro area of North Carolina. On the basis of lithologic comparison alone, the Lincolnton metadacite and associated felsic pyroclastic sequence are also interpreted to be equivalent to the Persimmon Fork Formation near Columbia, South Carolina. Prominent argillite units that overlie felsic metavolcanics in all three areas are likewise considered correlative. These units include the Tillery Formation (Albemarle-Denton-Asheboro area), the Richtex Formation (Columbia, South Carolina, area), and the upper sedimentary sequence (Lincolnton, Georgia-McCormick, South Carolina, area). Available data suggest a Cambrian age for most of these units, although some of the lowermost formations could actually be of very late Precambrian age.

Abstract The Carolina slate belt includes volcanic and sedimentary rocks of Late Precambrian and Cambrian age, metamorphosed to lower greenschist facies, that extend through the Piedmont from Georgia to Virginia. The segment in central North Carolina (Fig. 1) is probably the best-known part of the belt. Rocks in the Albemarle area are mildly deformed and metamorphosed; the dominant structures are open folds plunging southwest and the regional metamorphism is chlorite and biotite grade. The Albemarle region includes type localities for several stratigraphic units. The localities described here are on the Albemarle (Conley, 1962) and Denton (Stromquist, Choquette, and Sundelius, 1971) 15-minute quadrangles. The guidebook by Stromquist and Conley (1959) marked the beginning of modern studies in the central Carolina slate belt, as they demonstrated that stratigraphy and structure could be worked out on a regional basis. Conley and Bain (1965) applied formation names to the section in the Albemarle area (Fig. 2) and extended this stratigraphic nomenclature through most of the slate belt in North Carolina. In the Albemarle region, a thick, dominantly felsic volcanic unit (Uwharrie Formation) is overlain by a dominantly sedimentary sequence (Albemarle Group). The Morrow Mountain Rhyolite and Badin Greenstone of the Tater Top Group were interpreted to be the uppermost units and to lie with angular unconformity above folded older units (Conley and Bain, 1965). Stromquist and Sundelius (1969) reinterpreted part of the middle and upper stratigraphic sequence. They considered the Tater Tbp Group to be interlayered with other units of the Albemarle Group, rather than

Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb ages of more than 400 detrital zircons from the Neoproterozoic–early Paleozoic clastic sequences of Carolinia range from ca. 530 Ma (Early Cambrian) to ca. 2600 (Archean). The majority of analyzed zircon grains are late Neoproterozoic (Ediacaran), with minor amounts of Mesoproterozoic–Paleozoic and accessory Archean grains. The overall distribution of age populations of detrital zircons is consistent with sediment derivation from the Amazonian craton and its peripheral orogenic belts on the margin of west Gondwana. On the basis of the age of the youngest detrital zircon populations (ca. 550 Ma), the Uwharrie, Tillery, Cid, and Yadkin formations are no older than Ediacaran. The minimum depositional ages of the Uwharrie and Cid formations are constrained by ages of contemporaneous volcanism (551 ± 8 and 547 ± 2 Ma, respectively). Thus, all units of the Albemarle sequence were deposited between ca. 550 and 532 Ma. The dominance of Ediacaran and early Paleozoic zircons in the Albemarle Group suggests an underlying local protosource for the sediments. Mesoproterozoic and older detrital grains constitute a minor component and have an age signature that suggests derivation from the underlying continental crust basement. Dated samples from the Albemarle Group yield similar detrital zircon U-Pb age popu lations consistent with a common provenance. The results of this study illustrate that sedimentation in the Albemarle sequence of Carolinia is a manifestation of active tectonics and occurred broadly coeval with felsic magmatism. These relationships suggest that magmatism, tectonism, and deposition were broadly coeval and important regional-scale mechanisms consistent with formation in a late Neoproterozoic–early Paleozoic arc rift to backarc basin tectonic setting.