Date of Award:
8-2024
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Geosciences
Committee Chair(s)
Carol Dehler
Committee
Carol Dehler
Committee
C. Evelyn Gannaway Dalton
Committee
Donald Penman
Abstract
Within the siliciclastic-sediment-dominated Bright Angel Formation (BAF) of the iconic Cambrian sedimentary strata (Tonto Group) in Grand Canyon National Park, Arizona, workers have identified and named prominent reddish-brown cliffs breaking up the generally slope-forming unit near, but separated from, its upper contact with the limestone-dominated Muav Formation, the "Rusty Brown Dolostones" (RBDs). Previous hypotheses suggest that the RBDs are chemically and physically altered tongues of the Muav Formation intercalated with the BAF at increasingly higher stratigraphic positions from west to east within the Canyon. A genetic association between the Muav Formation and the RBDs, as well as between the RBDs themselves, has yet to be established. Further, the paleoenvironment that these apparent couplets represent is poorly constrained. Understanding the formation and evolution of these deposits will fill a gap in our understanding that sits at a prominent transition in facies belts and thus depositional environments, elucidating processes that link two distinct belts of rock formed on the Cambrian Laurentian margin during a period of gradual sea level rise (termed the Sauk Transgression).
Here we use sedimentological observations and stratigraphic relationships to interpret the paleoenvironmental conditions that resulted in the deposition of the RBDs and provide a single more widely applicable definition of the member. We define the RBDs as sets of coupled repeating depositional cycles composed of subtidal marine shales, siltstones, and well-sorted fine-grained, glauconitic quartz arenites (sandstones). These packages transition upwards into iron enriched carbonates that span a genetic spectrum from apparently abiotic, to biotically-influenced, to biotically-mediated. These are interpreted as lagoonal to estuarine deposits influenced by tides, formed in a peritidal to shallow subtidal zone, and punctuated by storms that transition upsection into landward tongues of the Muav Formation developed during rising relative sea level. These sequences are subsequently overlain by BAF siliciclastic suites that advance seaward following the cessation of relative sea level rise. Sedimentological and geochemical analyses indicate a lack of subaerial exposure prior to burial and derivation of the ions necessary to transition these limestones into dolostones enriched in iron from the clay/mica mineral glauconite during shallow to intermediate burial alteration processes.
Checksum
74d13b892725b3c56e6d49647df00032
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.
Recommended Citation
Clevenger, Joseph J., "Shaking Off the Rust: Unraveling the Depositional and Diagenetic History of Enigmatic Ferroan Dolostones in the Cambrian Bright Angel Formation, Tonto Group, Grand Canyon" (2024). All Graduate Theses and Dissertations, Fall 2023 to Present. 300.
https://digitalcommons.usu.edu/etd2023/300
Included in
Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .