Late Shortening and Extensional Structures and Veins in the Western Margin of the Taconic Orogen (New York to Vermont)

Abstract

Abstract Along the western margin of the Taconic orogen in New York and Vermont, undeformed quartz‐calcite veins commonly occur in the belt of melange that formed beneath the westward‐advancing Taconic Allochthon during the Middle‐Late Ordovician Taconic orogeny. The veins have mineral slickenfibers recording either reverse or normal slip. In New York, the reverse‐motion veins recording the latest phase of shortening are crosscut by the normal‐motion veins and faults. The shortening indicated by the reverse‐motion veins is correlated with the convergence along the Champlain thrust in Vermont, which is also crosscut by a significant, strike‐parallel normal fault. Fluid inclusion data from the veins, complemented by stable isotope data, lead to a reconstruction of the sequence of events in the context of a cooling of the fluids, which is consistent with crosscutting relationships among the veins. Following cessation of the convergence, there was regional extension of the western margin of the Taconic orogen...