PETROGRAPHY AND DETRITAL ZIRCON GEOCHRONOLOGY OF CRETACEOUS SANDS: IMPLICATIONS FOR PROVENANCE IN WESTERN MISSISSIPPI EMBAYMENT

The Mississippi Embayment (MSE) is a wedge-shaped southward-plunging basin of ~259,000 km2 in the Gulf Coastal Plain that extends from southern Illinois and fans out into parts of AL, AR, KY, LA, MS, MO, TN, and TX. It is filled with Jurassic (~201.3 Ma to 145.5 Ma) to recent strata. Cretaceous deposits in the western Mississippi Embayment (WMSE) are significant for establishing sediment accumulation and dispersal patterns during and after the reactivation of the late Proterozoic and early Paleozoic Reelfoot rift system at the end of the Mesozoic Era. We report a Petrographic study and U-Pb ages of detrital zircons in unlithified sands from Cretaceous deposits in the WMSE to track their provenance and interpret sediment transport pathways and sediment sources. Preliminary observations of these unlithified sands reveal dominant quartz, sedimentary lithics, few feldspars, micas, and detrital matrix with clay minerals like glauconite. Minor rutile, and magnetite are also present in the heavy fraction. The zircon morphology is sub-rounded to well-rounded with minor euhedral crystals, displaying colors ranging from colorless to pale yellow to purple. Rounded crystals suggest mechanical weathering during transport, and euhedral crystals suggest potential preservation from proximal sources. Additionally, the zircons exhibit a range of shapes from tabular to prismatic, ranging in size from ~100µm to 500µm, further suggesting contributions from multiple sources. Hence, we hypothesize that a significant portion of this material originates from a short transport distance with a mixed provenance from nearby orogenic belts and other distal sources, primarily from the central to western Laurentian craton.