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Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

Edgar, Lauren A. and Grotzinger, John P. and Palucis, Marisa (2018) Shaler: in situ analysis of a fluvial sedimentary deposit on Mars. Sedimentology, 65 (1). pp. 96-122. ISSN 0037-0746.

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This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

Item Type:Article
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URLURL TypeDescription
Edgar, Lauren A.0000-0001-7512-7813
Grotzinger, John P.0000-0001-9324-1257
Palucis, Marisa0000-0003-0034-5810
Additional Information:© 2017 The Authors. Sedimentology published by John Wiley & Sons on behalf of International Association of Sedimentologits. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Manuscript received 5 September 2016; revision accepted 6 March 2017. The authors gratefully acknowledge support from the NASA Mars Science Laboratory Mission and the efforts of the MSL engineering and science operations teams. We thank Neil Davies and an anonymous reviewer, whose comments have improved the manuscript. Sanjeev Gupta acknowledges funding from the UK Space Agency (UKSA) and the Science and Technology Funding Council (STFC). Data presented in this paper are archived in the Planetary Data System (
Funding AgencyGrant Number
United Kingdom Space Agency (UKSA)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:Fluvial; Gale crater; Mars; sedimentology; stratigraphy
Issue or Number:1
Record Number:CaltechAUTHORS:20171212-144758072
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Official Citation:Edgar, L. A., Gupta, S., Rubin, D. M., Lewis, K. W., Kocurek, G. A., Anderson, R. B., Bell, J. F., Dromart, G., Edgett, K. S., Grotzinger, J. P., Hardgrove, C., Kah, L. C., Leveille, R., Malin, M. C., Mangold, N., Milliken, R. E., Minitti, M., Palucis, M., Rice, M., Rowland, S. K., Schieber, J., Stack, K. M., Sumner, D. Y., Wiens, R. C., Williams, R. M. E. and Williams, A. J. (2018), Shaler: in situ analysis of a fluvial sedimentary deposit on Mars. Sedimentology, 65: 96–122. doi:10.1111/sed.12370
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83838
Deposited By: Tony Diaz
Deposited On:12 Dec 2017 23:00
Last Modified:03 Oct 2019 19:11

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