Type of Submission
Poster
Keywords
geology, sandstone, Coconino, carbonate, subaqueous
Proposal
Carbonate material is found widely throughout the Permian Coconino sandstone. One outcrop north of Ash Fork, Arizona is observed to contain a carbonate-rich lens. Conventional interpretation attributes the Coconino to eolian processes. This research aims to propose a mechanism of formation for the lens based on thorough site investigation and laboratory analyses. Methods include field observation and thin section description, as well as particle size, XRD, and SEM analyses. The resulting data revealed that the lens contains high percentages of calcite, with sparse dolomite rhombs. Muscovite, K-feldspar, and plagioclase were observed, and quartz sand grains were found to be subangular and pitted from carbonate dissolution. Illite was observed to be both detrital and authigenic. Lens-shaped carbonate features were also found in the Coconino near Hermits Rest, Grand Canyon, with similar features to that of the Ash Fork outcrop. While the Coconino is conventionally interpreted as an eolian deposit, the extent of this carbonate in conjunction with its textural features implies that subaqueous processes likely deposited this sandstone. This combination of observations supports a subaqueous depositional model for the Coconino sandstone
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Publication Date
2024
Carbonate in the Coconino Sandstone Near Ash Fork, Arizona
Carbonate material is found widely throughout the Permian Coconino sandstone. One outcrop north of Ash Fork, Arizona is observed to contain a carbonate-rich lens. Conventional interpretation attributes the Coconino to eolian processes. This research aims to propose a mechanism of formation for the lens based on thorough site investigation and laboratory analyses. Methods include field observation and thin section description, as well as particle size, XRD, and SEM analyses. The resulting data revealed that the lens contains high percentages of calcite, with sparse dolomite rhombs. Muscovite, K-feldspar, and plagioclase were observed, and quartz sand grains were found to be subangular and pitted from carbonate dissolution. Illite was observed to be both detrital and authigenic. Lens-shaped carbonate features were also found in the Coconino near Hermits Rest, Grand Canyon, with similar features to that of the Ash Fork outcrop. While the Coconino is conventionally interpreted as an eolian deposit, the extent of this carbonate in conjunction with its textural features implies that subaqueous processes likely deposited this sandstone. This combination of observations supports a subaqueous depositional model for the Coconino sandstone
