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Abstract: Compositional Variations and Tectonosedimentary Conditions of the Atokan Deltaic Sediments, Arkansas

Tanwi Gangopadhyay, Ezat Heydari

Detailed petrographic studies were conducted to determine the compositional variations and the influences of tectonics on the deposition of the Pennsylvanian Atokan deltaic sediments in Arkansas. The rocks have a composition of Q82-90F3-10R5-19 and are classified as sublitharenites. Quartz is dominated by monocrystalline types (82-71%) with minor amounts of polycrystalline variety (3-7%). Feldspars constitute a minor proportion (K-feldspar 2-5%; plagioclase feldspar 0-4%); the lithics (5-12%) are composed of metamorphic and sedimentary fragments. Paleocurrent data and high percentage of quartz suggest that sediments were primarily derived from the northern craton. However, metamorphic and sedimentary rock fragments imply the Appalachians a a secondary source area. Point counting via the Gazzi-Dickinson technique indicates that all rocks are of a recycled orogen. The high quartz content, and a dearth of feldspars indicate that warm and humid climate and low relief extensively altered the primary mineralogic signatures in the source area. Comparison of compositional variations of the Stanley, the Jackfork, and the Atoka Formations will shed light on the late Paleozoic tectonic evolution of the basin.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana