Regional thermal overprinting during Mesozoic rifting recorded by sphene and zircon fission track dates, central Appalachian Piedmont, U.S.A

Abstract

A total of 12 sphene and 47 zircon fission track ages (FTA) are reported from Grenville and Taconic crystalline rocks and the Mesozoic Newark Series of the central Appalachian Piedmont. All FTA fall within a relatively restricted range of 165-215 Ma. Sphene FTA (average 197 Ma) and zircon FTA (average 182 Ma) are nearly concordant within the analytical errors. FTA are interpreted as indicating relatively rapid cooling from sphene to zircon closure temperatures (ca. 280-200°C) between the times indicated by the dates. Near concordance of FTA over the study area (ca. 16,000 km2) is indicative of cooling following total annealing during a regional thermal event. Independent evidence for high he..