DETRITAL-ZIRCON GEOCHRONOLOGY OF ACADIAN FORELAND BASIN STRATA OF WEST VIRGINIA AND VIRGINIA

Detrital zircons with 238 U-206 Pb ages of 400 – 600 Ma have been rarely reported in Devonian units of the central and southern Appalachian foreland basin, although significant numbers of ‘Taconic' (440-490 Ma) zircons presumably derived from the tectonic hinterland have been identified in Devonian sandstones of the northern Appalachians. This apparent discrepancy in sandstone composition or provenance may be caused by different sampling locations within the foreland basin system (i.e., wedge-top vs. foredeep depozones) or due to a lack of Devonian samples analyzed from the central and southern parts of the basin. Here we report U-Pb detrital-zircon ages collected from Paleozoic sandstones in West Virginia and Virginia.

Detrital-zircon samples collected from Devonian synorogenic clastic wedges of the central Appalachian foreland basin (N = 3, n=289) have various age populations including those coeval with early Paleozoic (‘Taconic') magmatism (ca. 440-490 Ma), the Grenville orogen and associated Granite-Rhyolite Province (0.9-1.5 Ga), the Pan-African orogen (0.5-0.7 Ga), the Mid-Continent and Central-Plains orogens (1.6-1.9 Ga) and Superior Province (ca. 2.7 Ga). On the other hand, samples (N = 4, n=383) collected from Devonian and Silurian units deposited during interpreted orogenic quiescence are dominated by Grenville and associated Granite-Rhyolite Province zircons with minor contributions from the Mid-Continent, Central-Plains orogens and Superior provinces, but do not contain zircons coeval with early Paleozoic Appalachian magmatism and the Pan-African orogen.