Anatomy of exhumed river-channel belts: Bedform- to belt-scale kinematics of the Ruby Ranch Member, Cretaceous Cedar Mountain Formation, Utah, USA

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Benjamin T. Cardenas, David Mohrig, Timothy A. Goudge, Cory M. Hughes, Joseph S. Levy, Travis Eric Swanson, Jasmine Mason, Feifei Zhao


Many published interpretations of ancient fluvial systems have relied on observations of extensive outcrops of thick successions. This paper, in contrast, demonstrates that a regional understanding of paleoriver kinematics, depositional setting, and sedimentation rates can be interpreted from local sedimentological measurements of bedform and barform strata. Dune and bar strata, channel planform geometry, and bed topography are measured within exhumed fluvial strata exposed as ridges in the Ruby Ranch Member of the Cretaceous Cedar Mountain Formation, Utah, USA. The ridges are composed of lithified stacked channel belts, representing at least 5 or 6 reoccupations of a single-strand channel. Lateral sections reveal well-preserved barforms constructed of subaqueous dune cross sets. The topography of paleobarforms is preserved along the top surface of the outcrops. Comparisons of the channel-belt centerline to local paleotransport directions indicate channel planform geometry was preserved through the re-occupations, rather than being obscured by lateral migration. Rapid avulsions preserved the state of the active channel bed and its individual bars at the time of abandonment. Inferred minimum sedimentation durations for the preserved elements, inferred from cross-set thickness distributions and assumed bedform migration rates, vary within a belt from one to ten days. Using only these local sedimentological measurements, the depositional setting is interpreted as a fluvial megafan, given the similarity in river kinematics. This paper provides a systematic methodology for the future synthesis of vertical and planview data, including the drone-equipped 2020 Mars Rover mission to exhumed fluvial and deltaic strata.



Earth Sciences, Geology, Physical Sciences and Mathematics


channel belt, fluvial, cross set, dune, bar, centerline, cross strata, preservation, sinuous ridge, stratigraphic time


Published: 2019-08-30 07:37

Last Updated: 2020-05-19 07:54

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GNU Lesser General Public License (LGPL) 2.1

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