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

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Title: Shaler: in situ analysis of a fluvial sedimentary deposit on Mars
Author(s): Edgar, L
Gupta, S
Rubin, DM
Lewis, KW
Kocurek, GA
Anderson, RB
Bell, JF
Dromart, G
Edgett, KS
Grotzinger, JP
Hardgrove, C
Kah, LC
Leveille, R
Malin, MC
Mangold, N
Milliken, RE
Minitti, M
Palucis, M
Rice, M
Rowland, SK
Schieber, J
Stack, KM
Summer, DY
Wiens, RC
Williams, RME
Williams, AJ
Item Type: Journal Article
Abstract: This paper characterises 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 characterisation of the sedimentology of such fluvial deposits has not previously been possible. Results from NASA’s 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 likely 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 northeast, across the surface of a bar that migrated southeast. 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 suggests 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.
Publication Date: 21-Jun-2017
Date of Acceptance: 22-Feb-2017
ISSN: 1365-3091
Publisher: Wiley
Start Page: 96
End Page: 122
Journal / Book Title: Sedimentology
Volume: 65
Issue: 1
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/J005169/1
Copyright Statement: ©2017 The Authors.Sedimentologypublished by John Wiley & Sons on behalf ofInternational Association of SedimentologitsThis 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
Keywords: Science & Technology
Physical Sciences
Gale crater
0403 Geology
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering

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