DETRITAL-ZIRCON GEOCHRONOLOGY OF APPALACHIAN FORELAND BASIN STRATA IN THE CENTRAL AND SOUTHERN APPALACHIANS: THE CHANGES OF SEDIMENTARY SOURCES FROM THE TACONIC THROUGH THE ALLEGHANIAN

The U-Pb age spectra of detrital zircons collected from Appalachian foreland basin strata allow us to characterize the provenance of Paleozoic sedimentary rocks in the central and southern Appalachian basin and to better understand Appalachian kinematic history. Samples from Taconic clastic wedges are predominated by 1080-1180 Ma and 1300-1500 Ma zircons contemporaneous with the Shawinigan phase of the Grenville orogeny and magmatism in the Granite-Rhyolite province, respectively. Samples from Acadian clastic wedges contain relatively large populations of Early Paleozoic zircons, and minor populations of 500-700 Ma and 1900-2200 Ma zircons that are consistent with a Gondwanan affinity. Samples from Alleghanian clastic wedges display large populations of 980-1080 Ma zircons consistent with the Ottawan phase of the Grenville orogeny, increased abundance of 2700 Ma and older Archean zircons, and decreased abundance of Paleozoic zircons. The changes in age populations of detrital zircons in Appalachian foreland basin strata indicate that distal sources from Grenville and associated Granite-Rhyolite provinces are the most important sources during the Taconic orogeny, but frontal orogen and orogenic hinterland sources from Paleozoic magmatic arcs and associated metasedimentary rocks comprise more important components in sedimentary records during the Acadian and Alleghanian orogenies. The abundant appearance of Early Paleozoic detrital zircons in Acadian synorogenic clastic wedges suggests that a significant terrane accretion event to Laurentian margin occurred in the Devonian time. Further, the younging-upward age progression in Grenville province sources revealed in Taconic through Alleghanian successions indicates the evolution of Grenvillian crust in the central Appalachians.