Detrital Zircon U-Pb Geochronology of Upper Mississippian Siltstone, Oklahoma and Arkansas

Although Upper Mississippian strata have been characterized extensively using lithostratigraphy, sequence stratigraphy, and biostratigraphy across the North American midcontinent, the origin of the silt comprising the Meramec STACK (Sooner Trend Anadarko Basin, Canadian and Kingfisher counties) reservoirs of the Anadarko Basin in west-central Oklahoma and age equivalent units is not well understood, despite its economic importance as an unconventional petroleum reservoir. Previously published models have variously invoked fluvial, marine, and aeolian sediment transport for Upper Mississippian siltstone present along the paleo-shelf edge of the Laurentian craton. This study uses detrital zircon U-Pb geochronology and grain morphology, handheld x-ray fluorescence (hXRF) whole rock geochemistry, and petrography to constrain sediment provenance of Upper Mississippian (Meramecian and Chesterian) strata along the Laurentian paleo-shelf edge. Conservative mineral separation techniques were developed to facilitate processing of silt-sized material, allowing efficient recovery in small (i.e., \u3c100 \u3eg) samples. Detrital zircon U-Pb age and grain morphology data reported in this study indicate that Upper Mississippian silt-sized detritus was not only sourced from to Laurentia but was also sourced from advancing peri-Gondwanan terranes to the south and/or east. Of the 2478 detrital zircon analyses measured from nineteen Meramecian siltstone samples, 32% were Grenville (900-1350 Ma), 21% were Appalachian (240-500 Ma), and 17% were peri-Gondwanan (500-900 Ma). Zircon grain size and morphology data complements U-Pb age data and provides additional insight into potential sediment transport mechanisms of the Meramecian silt. Peri-Gondwanan detrital zircons (500-900 Ma) are smaller and more spherical than Appalachian (240-500 Ma) or Grenville (900-1300 Ma) zircon, suggesting that these peri-Gondwanan grains may have traveled greater distances. Age-equivalent samples on the craton of Laurentia do not possess a significant component of 500-900 Ma zircon, suggesting peri-Gondwana grains along the paleo-shelf edge were transported via marine currents rather than by wind. The combination of detrital zircon U-Pb ages, morphology data, and petrographic observations support a model for long-distance transport of peri-Gondwanan zircon to the southern Laurentian margin via contour-parallel marine currents. These far travelled grains mixed with detritus sourced from the easterly Appalachian Orogeny along the southern paleo-shelf edge of Laurentia. This study documents a significant peri-Gondwanan influence in the southern midcontinent of North America during Meramecian time, the presence of which predates the consequent arrival of these southerly terranes during the collision of southern Laurentia with Gondwana