New structural mapping and U-Pb sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) zircon analysis on rocks of the WNW-dipping, fault-bounded Nashoba-Putnam terrane in southeastern New England, USA, were used to further constrain its structural and metamorphic history, and test a hypothesis of channel flow and ductile extrusion. The Nashoba-Putnam terrane is an early Paleozoic arc/back-arc complex on the trailing edge of Gondwana-derived Ganderia. It consists of high-grade partially melted rocks between mostly lower-grade rocks in adjacent domains, resembling a ductile extrusion zone.Isoclinal folds are locally refolded by northwest-side-down asymmetric folds throughout the Nashoba-Putnam terrane, and by additional northwest-side-up folds in the southeastern part of the Nashoba terrane and locally in the Putnam terrane to the south. Structures generally dip shallower towards the southern part of the Nashoba terrane and in the Putnam terrane.New SHRIMP-RG data indicate that partial melt occurred at ∼422 Ma in the eastern part of the Nashoba terrane, and at ∼364 Ma in the southern part. Structures and the partial melt history of the southeastern Nashoba terrane are consistent with the center of a previously interpreted Late Silurian–Devonian ductile extrusion zone, of which the top lies in the northwestern part of the terrane. The bottom may lie in an adjacent high-grade metamorphic zone of the Avalon terrane to the southeast or have been removed by a fault. The younging of deformation and metamorphism, and shallowing of structures in the southern Nashoba, and Putnam terranes may be an effect of the Carboniferous–Permian assembly of Pangea.
