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Fluvial Sinuous Ridges of the Morrison Formation, USA: Meandering, Scarp Retreat, and Implications for Mars

Hayden, A. T. and Lamb, M. P. (2020) Fluvial Sinuous Ridges of the Morrison Formation, USA: Meandering, Scarp Retreat, and Implications for Mars. Journal of Geophysical Research. Planets, 125 (10). Art. No. e2020JE006470. ISSN 2169-9097. doi:10.1029/2020JE006470.

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Sinuous ridges have been interpreted as evidence for ancient rivers on Mars, but relating ridge geometry to paleo‐hydraulics remains uncertain. Three analog ridge systems from the Morrison Formation, Utah, are composed of sandstone caprocks, up to 50 m wide and 8 m thick, atop mudstone flanks. Ridge caprocks have narrowed significantly compared to sandstone bodies preserved in outcrop, consistent with a new ridge‐erosion model that can be used to estimate original sandstone‐body extent. Ridge networks represent caprocks intersecting at distinct stratigraphic levels, rather than a preserved channel network. Caprocks are interpreted as amalgamated channel belts, rather than inverted channels, with dune and bar cross stratification that was used to reconstruct paleo‐channel dimensions. Curvilinear features on ridge tops are outcropping lateral accretion sets (LAS) from point bars and indicate meandering. We found that caprock thickness scales with paleo‐channel depth and LAS curvature scales with paleo‐channel width. Application of these relations to a ridge in Aeolis Dorsa, Mars, yielded consistent water discharge estimates (310–1,800 m³/s). In contrast, using ridge width or ridge radius of curvature as paleo‐channel proxies overestimated discharge by a factor of 30–500. In addition, the ridge‐erosion model suggests that scarp retreat may be less efficient on Mars, resulting in taller and wider ridges, with more intact caprocks. Altogether, our results support the hypothesis that ridges are exhumed channel belts and floodplain deposits implying long‐lived fluvial activity recorded within a depositional basin.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemLidar DEM of Ferron Creek field sites ItemHiRISE stereo DEMs
Hayden, A. T.0000-0003-3540-7807
Lamb, M. P.0000-0002-5701-0504
Additional Information:© 2020 American Geophysical Union. Issue Online: 28 September 2020; Version of Record online: 28 September 2020; Accepted manuscript online: 12 September 2020; Manuscript accepted: 09 September 2020; Manuscript revised: 03 September 2020; Manuscript received: 27 March 2020. The authors wish to thank the members of Caltech's fall 2015 advanced field course (Joe Biasi, Austin Chadwick, Florian Hoffman, Ellen Leask, Luca Malatesta, and Marshall Trautman) for field assistance. Thanks to Jay Dickson for the HiRISE stereo DEM analyzed in Figure 17 and to NSF National Center for Airborne Laser Mapping for the lidar for the Ferron Creek sites (seed grant Project ID 2016‐06). Thanks also to T. A. Goudge and R. M. E. Williams for their formal reviews that helped us improve the manuscript. This work was supported by NASA (grant NNX16AQ81G to M. P. L. and graduate fellowship support 80NSSC17K0492 to A. T. H.). Data Availability Statement: Supporting information includes Table S1 (raw ridge measurements), Table S2 (raw sedimentology measurements), and Table S3 (summary measurements). The lidar DEM of the Ferron Creek field sites is on the NCALM website (, and the HiRISE stereo DEMs are accessible on the Geoscience node of the NASA Planetary Data System (
Funding AgencyGrant Number
Subject Keywords:Mars; Inverted channel; Sinuous ridge; Scarp retreat; Paleohydrology; Analog study
Issue or Number:10
Record Number:CaltechAUTHORS:20200922-070057374
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Official Citation:Hayden, A. T., & Lamb, M. P. (2020). Fluvial sinuous ridges of the Morrison Formation, USA: Meandering, scarp retreat, and implications for Mars. Journal of Geophysical Research: Planets, 125, e2020JE006470.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105463
Deposited By: Tony Diaz
Deposited On:22 Sep 2020 17:56
Last Modified:16 Nov 2021 18:43

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