Depositional and tectonic setting of the Neoproterozoic-early Paleozoic rocks of theVirgilina sequence and Albemarle Group, North Carolina

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb ages ofmore than 400 detrital zircons from the Neoproterozoic-early Paleozoic clastic sequencesof Carolinia range from ca. 530 Ma (Early Cambrian) to ca. 2600 (Archean). The majority ofanalyzed 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 ageof 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 conti nental 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.