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Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Abstract The pre-Jurassic rocks of Corridor E-3 as shown in the Main Display, West Sheet, reveal the tectonic history of the middle Atlantic margin of the North American continent during the interval Late Proterozoic through Tertiary. The history is graphically shown on the main display and is also summarized in the conclusions of this paper. This corridor differs from other eastern margin corridors in four important respects; 1) there is a large uplift of IGa Grenville basement in the eastern Piedmont at this latitude. 2) Only one suture (early Taconic, Cambrian - Late Ordivician) is recognized in the exposed Appalachians, and that separates the Carolina (Avalon) magmatic terrane from the Laurentian passive margin. 3) The Chopawamsic/ James Run volcanic belt is recognized as a part of Carolinia/Avalonia, and is not a different island arc. 4) The eastern margin of Laurentia (and its upper bounding surface, the early Taconic suture) extends in the subsurface below the coastal plain at least 50 kilometers east of Richmond in one model, or may reach the continental edge in another. Bird and Dewey (1970) produced the first comprehensive modern tectonic model that included the central and southern Appalachians. It was essentially an extrapolation of northern Appalachian and Newfoundland data into the southeast. However, a model based primarily on northern Appalachian geology didn't seem to fit the central and southern Appalachians and, in 1972 Robert D. Hatcher, Jr., attempted the first comprehensive tectonic model for the southern Appalachians. His model proposed that the eastern Piedmont volcanics, (Charlotte,

Abstract Paleozoic rocks exposed in the Appalachian Mountains are bordered on the east and south by the Atlantic and Gulf Coastal Plains, and rocks of the Paleozoic orogenic belt may be traced beneath the cover of post-orogenic Mesozoic-Cenozoic Coastal Plain strata (Plate 6). Large-scale lithotectonic components of the exposed Appalachian orogen include the foreland fold-thrust belt and internal metamorphic belts (collectively called the Appalachian Piedmont), which locally contain internal basement massifs. External basement massifs and discontinuous belts of low-grade metamorphic rocks are distributed along the boundary between the fold-thrust belt and the Piedmont. Accreted terranes are identified in the internal metamorphic belts.

This study documents an eruptive center, the instrusive Flat River complex and associated Carolina slate belt volcanic rocks near Durham, North Carolina. The zircon Pb/U age of the granite, granodiorite, quartz diorite, gabbro Flat River complex is 650 ± 30 m.y. Local vent breccias, chilled and protoclastically deformed margins, and petrographic comparisons with the experimental results in the qz-ab-or system confirm that the Flat River complex was emplaced at a depth of less than 1 km and was locally surface breaking. Thus, the Flat River can be viewed as a very shallow fossil volcanic magma chamber and may be typical of many granitoid plutons in the Carolina slate belt. The Flat River was intruded into a pile of coarse, near-vent pyroclastic deposits and lavas of felsic to intermediate composition. Intercalated in these is an exhalative unit of thinly layered to laminated metachert and iron oxide. Shallow to deep (or quiet) probably marine conditions prevailed. Some subaerial pyroclastic rocks may be present in the older parts of this >650-m.y. to 620-m.y.-old sequence of volcanic rocks.