PROVENANCE EVOLUTION DURING ASSEMBLY OF THE ACADIAN/NEOACADIAN OROGEN: DETRITAL ZIRCON DATA FROM THE DEVONIAN OF NEW YORK

New U-Pb detrital zircon data from the classic Devonian stratigraphic sequence in the Catskill region of New York State document the evolution of terrigenous clastic sources during the assembly of the Appalachian Orogen. Zircon populations from middle to upper Lower Devonian (Pragian and Emsian Stages) strata are dominated by Grenville (ca. 1400-1000 Ma) and older grains, derived largely from older Paleozoic clastic rocks that were originally sourced from the Laurentian craton. Lower Middle Devonian (Eifelian to lowest Givetian) siliciclastics, including the Marcellus subgroup, are dominated by Laurentian sources, with younger Grenville (Ottawan, ca. 1080-1020 Ma) zircons most abundant. This may suggest direct unroofing of Grenville basement source rocks during Marcellus deposition.

Upper Middle Devonian (Givetian) clastics are dominated by Grenville zircons, but include larger ca. 470-420 Ma populations from igneous and metamorphic sources within the Appalachian Orogen. Lower Upper Devonian (Frasnian) strata contain zircon suites signaling new source terranes including Neoproterozoic ‘peri-Gondwana’ (ca. 950-540 Ma) source rocks. Zircon populations from the lower Frasnian Oneonta Formation document an abrupt shift to a provenance with much greater abundance of Neoproterozoic age materials, related to the unroofing of previously unexposed source rocks. Nd-Sm data from basinward equivalents of the Oneonta also indicate the input of more juvenile clastic material. The younger Frasnian strata (Walton and Slide Mountain Formations) contain relatively fewer Neoproterozoic zircons, and increased contributions from Paleozoic igneous and metamorphic sources.