Browsing by Author "Heinzel, Chad Elliott"

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    Stratigraphic, Petrographic, and Sedimentologic Analysis of Upper Cretaceous Deltaic Sedimentation of the Adaville Formation, Kemmerer Coal Mine Area, Southwestern Wyoming
    (2000-02) Heinzel, Chad Elliott
    The Late Cretaceous Lazeart Member, the lower member of the Adaville Formation in southwestern Wyoming, has been interpreted as a wave-dominated deltaic complex. Studied sandstone outcrops include Crackers Point, Skull Point, and sandy layers within the Adaville Formation at the P&M Coal Mine near Kemmerer. The Adaville Formation, 620 m thick, consists of interbedded brownish shale, siltstone, sandstone layers, and coal seams. One coal bed exceeds 30 m in thickness. The average QmFLt ratio for the Adaville sandstones is 71:10:19; they are feldspathic sublitharenites. The average QmFLt ratio for the Lazeart sandstones is 58:10:32; they are classified as feldspathic lithic arenites. Petrographic study revealed the presence of quartz overgrowths, vermicular kaolinite, partially dissolved K-feldspars, silica cement, and clay matrix undergoing various stages of diagenesis. The average porosities of the Adaville Formation and Lazeart Member are 6.3 and 12.6 percent, respectively. Primary porosity has been decreased by quartz overgrowths and vermicular kaolinite. Two source areas contributed sediment to the Adaville Formation. The Idaho batholith shed metamorphic fragments, euhedral zircons, and K-feldspar-bearing plutonic fragments. In addition, Paleozoic sedimentary rocks thrust upward by the Absaroka and older faults contributed mud-siltstone fragments, rounded zircons, rounded tourmaline, and chert grains. Clastic debris from both source areas was transported along flu vial channels into a rapidly subsiding foreland basin adjacent to the Sevier Orogenic Belt. A regressive-transgressive epeiric seaway reworked sediments and placed morphologic constraints on the Lazeart wave-dominated delta.