CAT SQUARE TERRANE OF THE SOUTHERN APPALACHIAN PIEDMONT: A POST-ACCRETIONARY SALINIC BASIN RECORDING TERRANE DISPERSAL

The Cat Square terrane of the Southern Appalachian eastern Inner Piedmont formed as a Wenlock-Ludlow basin as Carolina rifted from Laurentia. Thus the Cat Square basin represents the (present-day) most southerly extent of the Boucot's “Salinic disturbance.” Basin sediments were deposited above an unconformity subsequently reactivated as the Brindle Creek fault. Basement to the Cat Square basin included the peri-Laurentian western IP (Tugaloo terrane) and exotic Carolina, and the Iapetan suture between these terranes, nowhere observed today. The CST records the telescoping of this basin during which it experienced extensive plutonism and metamorphism up to granulite facies in the Late Devonian. The BCf experienced significant retrogression ca. 323 Ma (Late Miss), at which time Carolina and the Inner Piedmont were juxtaposed again and shared a common tectonothermal history for the remainder of the Alleghanian orogen.

Structural analysis requires the IP and EBR be restored to their position along the Laurentian margin at the Dev-Miss boundary (ca. 360 Ma), inboard of the exposed PA-NY App, after removing more than 500 km dextral slip preserved within these terranes. Restored to this latitude, the relationship between the Cat Square basin and “classic” late Silurian Salinic basins – Connecticut Valley-Gaspé, central Maine, Fredericton Trough, La Poile Group of southwestern NFLD – becomes more clear. These basins formed following accretion of Ganderia to Laurentia as Iapetus closed in the Late Ordo. In the southern Appalachians, earliest basin sedimentation (post 430 Ma) is coeval with extensive plutonic activity (partial melting of crust?) and followed by (mantle-derived?) bimodal plutonism (Concord-Mecklenburg and Salisury-Southmont suites). These patterns are also recognized in the New England and Maritime App, where bimodal volcanism of the Tobique, Piscataquis, and Coastal Maine belts is observed.