Testing a northern Appalachian source for the Catskill-Pocono clastic wedge: Reconstructing Devonian–Mississippian sediment routing using detrital zircon and monazite geo-thermochronology

Abstract The Paleozoic Appalachian orogen extends >3000 km across eastern Laurentia and is largely composed of a mosaic of terranes representing multiple collisional orogenic phases that culminated in Pangea supercontinent assembly. We present new detrital zircon and monazite geo-thermochronology to investigate orogen–foreland basin sediment routing during the Devonian–Mississippian Acadian orogenic phase, which was a key interval for accretion of Gondwanan assemblages and orogenic plateau growth that accompanied a decrease in global temperature, marine mass extinctions, alpine glaciation, and deposition of the ~3.5-km-thick Catskill-Pocono siliciclastic wedge centered in Pennsylvania, USA. Previous work proposed the depositional system headwaters to the Catskill-Pocono clastic wedge were either in the northern or southern Appalachian orogenic highlands. Here, we test the northern versus southern source scenarios through the sedimentary provenance record of the Catskill-Pocono clastic wedge in central Pennsylvania using new double-dated detrital zircon (U-Th)/(He-Pb) and detrital monazite Th-Pb data. Detrital zircon U-Pb data are dominated by Taconic (490–420 Ma) and Grenville province (1350–900 Ma) ages and include minor Pan-African–Brasiliano–Iapetan rift (760–500 Ma), Proterozoic (1800–1350 Ma), and Archean (2700 Ma) age groups. In contrast, detrital monazite Th-Pb ages are mainly Acadian (425–375 Ma). When compared with previously published detrital zircon and monazite age signatures of potential sediment sources, detrital zircons are unable to pinpoint specific sources due to multiple generations of sediment recycling that cannot distinguish primary versus recycled sources. However, when detrital zircon data are paired with detrital monazite data, a northern Appalachian hinterland source is preferred for the Catskill-Pocono strata. The (U-Th)/He dates from Grenville- and Taconic-aged detrital zircons range from 440 Ma to 249 Ma and are interpreted as representing rapid source-rock cooling and exhumation during the Acadian orogeny. A Devonian–Mississippian paleo–sediment routing reconstruction is presented based on the along-strike evolution in Acadian foreland basin provenance exemplified by changes in the proportional abundance of Appalachian and Grenville zircon ages. Together, the detrital zircon and monazite data support a northern Appalachian source to the Devonian–Mississippian Acadian Catskill-Pocono siliciclastic wedge.