COMPETING LAURENTIAN AND GONDWANAN SEDIMENT SOURCES DURING PROTRACTED PANGEA ASSEMBLYIN THE MARATHON REGION OF WEST TEXAS

Suturing of Laurentia and Gondwana during Pangea assembly was a time-transgressive event that advanced westward from eastern Laurentia to the Marathon region. Strata exposed in the Marathon fold-thrust belt of west Texas preserve the stratigraphic record of pre- and syncollisional deposition. New multi-proxy sediment provenance data (detrital zircon U-Pb geochronology, thin section petrography, heavy minerals) from allochthonous Ordovician, Mississippian, and Pennsylvanian strata are used to reconstruct sediment source areas of the southern Laurentian margin during Pangea assembly. Similar methods were also applied to autochthonous Permian strata from the Guadalupe Mountains. Results from Ordovician strata reveal significant contribution of Neoproterozoic detrital zircons, consistent with derivation from peri-Gondwanan terranes during pre-collisional deposition. Mississippian Tesnus Fm. strata demonstrate mature sandstone petrofacies, and detrital zircon results yield Grenville and Taconic age signatures, consistent with sediment recycled from Laurentian sources. Two samples from the Pennsylvanian Haymond Formation reveal contrasting results compositions. Statistical methods confirm one is similar to Ordovician strata, suggesting recycling from proximal sources. The other is similar to typical Laurentian signatures, and may signal delivery from distal sources. The Pennsylvanian Gaptank Formation has a detrital zircon signature that is consistent with mixing of local sources that were potentially eroded from the fold-thrust belt. The Ordovician–Pennsylvanian results were modeled as potential sediment sources for Permian Brushy Canyon and Bell Canyon Formations from the Guadalupe Mountains. Mixture modeling suggests that Permian strata were sourced from Mississippian and Pennsylvanian strata along the Pangea suture, with additional contribution from Permian arc sources. These results support diverse and alternating Gondwanan and Laurentian sediment sources from both margins filling the remnant ocean basin, consistent with previous workers. These results also have implications for the sediment dispersal pathways that delivered sediment to the Permian Basin region.