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Using zircon geochronology to determine sand provenance in Northeast Oklahoma

Kleck, Kable
Tunin, Zac
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Abstract

Porosity in sandstones is a desired trait, but primary porosity is occluded in sandstone after reaching burial depths of 3 kilometers or more. However, depending on the sandstone's composition, secondary porosity can develop via dissolution of feldspars and metamorphic rock fragments. As sandstone is a sedimentary rock, it is made up of the detritus formed by the erosion of older rocks. The composition of sediments often reflects different geologic processes and unique sources. To determine where secondary porosity is likely to occur, it is necessary to reconstruct a sediment dispersal system. This study used petrography and U-Pb detrital zircon geochronology to ascertain the sedimentary provenance of the Cleveland and Seminole sandstones to reconstruct sediment dispersal patterns for Pennsylvanian age sandstones in northeastern Oklahoma. Samples were collected from two locations: Southern Hills Country Club outcrop in Tulsa, OK and the Sasakwa outcrop in Seminole County, OK. These samples were cut and made into thin sections for petrographic analysis and crushed and sent to the University of Arizona LaserChron lab to be processed for zircon recovery and U-Pb isotopic analysis. Petrographic analysis revealed the Southern Hills Country Club samples were dominantly quartz, feldspar and metamorphic rock fragments, whereas the Sasakwa samples were mostly quartz and chert. This difference in grain composition prompted the hypothesis that the Cleveland and Seminole sandstone came from different sources. Surprisingly, the zircon geochronology results indicated that zircons in both the Cleveland and Seminole sandstones were of the same provenance. This implies that while the petrography of the samples differs, the zircons and quartz share the same provenance. The metamorphic rock fragments and feldspars present in the Cleveland samples likely were weathered and dissolved before the Seminole Sandstone was deposited. Stable quartz grains and zircons were recycled in sediment that became the Seminole Sandstone. Detrital zircons retained their date of crystallization, preserving the matching age signatures.

Date
2020-04-24