Morphometry of a glacier-linked esker in NW Tempe Terra, Mars, and implications for sediment-discharge dynamics of subglacial drainage

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Butcher, Frances EG  ORCID logo
Gallagher, Colman 
Arnold, Neil S 

We present a systematic, metre-scale characterisation of the 3D morphometry of an esker on Mars, and the first attempt to reconstruct the multi-stage dynamics of esker formation on Mars. Eskers are sinuous ridges comprising sediment deposited by meltwater draining through ice-confined tunnels within or beneath glaciers. Detailed morphometric insights into eskers on Mars are important for (i) informing morphometric tests of whether sinuous ridges elsewhere on Mars are eskers, and (ii) informing modelling experiments which aim to reconstruct the glaciological and environmental controls on esker formation on Mars. We use a digital elevation model generated from High Resolution Imaging Science Experiment (HiRISE) images to characterise the height and width of an extremely rare esker associated with a late-Amazonian-aged viscous flow feature (debris-covered glacier) in NW Tempe Terra, Mars. Our measurements suggest that the NW Tempe Terra esker is a ‘stacked’ formation comprising an underlying ‘lower member’ ridge that is superposed by a narrower ‘upper member’ ridge. We used a novel morphometric approach to test whether the apparent stacking records two distinct esker deposition regimes (either within the same drainage episode, or within temporally-separated drainage episodes). This approach posits that esker crest morphology is controlled by primary esker formation processes and, by extension, that portions of eskers with similar crest morphologies should have similar morphometric relationships. We predicted the morphometric relationships described by the constituent upper and lower member ridges based on ‘reference relationships’ observed for morphologically-similar portions of the esker where no evidence of stacking was observed. Our observations corresponded well with the predicted relationships, supporting our stacked esker hypothesis. We propose conceptual models, which invoke spatial and temporal variations in sediment supply and meltwater discharge, to explain the stacked morphology. These models are informed by morpho-sedimentary relationships observed along eskers on Earth.

37 Earth Sciences, 3709 Physical Geography and Environmental Geoscience, 51 Physical Sciences, 3705 Geology
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Earth and Planetary Science Letters
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Elsevier BV
This work was un-dertaken at The Open University as part of a PhD studentship held by FEGB and funded by the Science Technology and Facil-ities Council (STFC) grant ST/N50421X/1. Manuscript preparation was supported by The Open University (internal funding) and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Advanced Grant PALGLAC 787263). We also gratefully acknowledge UK Space Agency grants ST/L00643X/1, ST/R001413/1, and ST/R001383/1 (MRB); ST/R001405/1, ST/P001262/1, and ST/S00145X/1 (SRL); and ST/R/001375 (AH). SJC is supported by the French space agency, CNES.