Abstract Recent detrital zircon results in both the central Appalachians and New England demonstrate that middle Ordovician, ‘Taconic’ island arcs, long considered to be peri-Laurentian, are built upon or associated with rock of Gondwanan affinity. This trip will visit granulite-facies orthogneiss of the Wilmington Complex, a 475–480 Ma magmatic arc, and the adjacent Wissahickon Formation. The Wissahickon Formation is intruded by and interlayered with meta-igneous rocks with arc affinity and contains detrital zircon populations characteristic of both Gondwanan and Laurentian sources. The Chester Park Gneiss, now known to have detrital zircon age spectra which match the Gondwana-derived Moretown Terrane in New England, is also featured. The trip will examine contact relationships between arc and Laurentian rocks and a newly discovered location where metapelitic rock contains garnet with crystallographically oriented rutile inclusions, possibly indicative of ultrahigh-temperature or ultrahigh-pressure metamorphism. We will discuss similarities between rocks of the central and northern Appalachians and evaluate a new model wherein the central Appalachian rocks were originally part of the Taconic arc in New England and were translated by strike-slip deformation to their present position in the orogen.

The osteichthyan paleofauna of the upper Pierre Shale Group has yielded range extensions for taxa known from its Sharon Springs Formation and the underlying Niobrara Formation, notably with the genera Protosphyraena and Pachyrhizodus . Links are now more apparent with Campanian and Maastrichtian (Late Cretaceous) paleofaunas from the Atlantic and Gulf Coasts of the United States, as with Cylindracanthus and Enchodus . Common elements are to be expected, considering the similarities in their geologic ages and environments of deposition.