Volcaniclastic aeolian deposits at Sunset Crater, Arizona: terrestrial analogs for Martian dune forms

Abstract

Sunset Crater in north-central Arizona (USA) is a 900-year-old scoria-cone volcano. Wind action has redistributed its widespread tephra deposit into a variety of aeolian dune forms that serve as a terrestrial analog for similar landforms and aeolian processes on Mars. Fieldwork was conducted to collect essential geomorphological and sedimentological data, and to establish a baseline for the type and morphometry of dunes, physical properties, interactions with topography, and saltation pathways. Our analyses focused primarily on coppice dunes, falling dunes, wind ripples, and sand streaks. For all collected volcaniclastic aeolian sediment samples, the sand-size fraction dominated, ranging from almost 100% sand to 74.6% sand. No sample contained more than 1.6% silt. The composition is overwhelmingly basaltic with non-basaltic particles composing 2 to 6% of the total. Coppice (nebkha) dunes form where clumps of vegetation trap saltating particles and create small mounds or hummocks. Mean grain size for coppice dune samples is coarse sand. Measured dune height for 15 coppice dunes ranged from 0.3 to 3.3 m with a mean of 1 m. Mean length was 6.7 m and mean width was 4.8 m. Falling dunes identified in this study are poorly developed and thin, lacking a prominent ramp-like structure. Mean wavelength for three sets of measured ripples ranged from 22 to 36 cm. Sand streaks extend downwind for more than a kilometer and are up to 200 m in width. They commonly occur on the lee side of mesas and similar landforms and are typically the downwind continuation of falling dunes. Falling dunes, wind ripples, and sand streaks have been identified on Mars, while coppice dunes are similar to Martian shadow or lee dunes in which sand accumulates in the lee of obstacles.

Planetary dune analogues: a special issue on integrating models, remote sensing and field data

“…Selecting sites with repeated passes of Mars Reconnaissance Orbiter (MRO), as well as those HiRISE scenes that offered high contrast between substrate and dark dune sands, has allowed for sand transport to be identified by scene subtraction between the image pairs within a GIS. These results are significant additions to the understanding of aeolian transport pathways for Mars and offer data that can be compared with terrestrial analogues in which direct analysis of source-to-sink settings are made (see, for example, in this Special Issue: Hooper et al, 2012;Tirsch et al, 2012). Significantly, layered sediments within the walls of two of the three intra-crater settings are likely sand sources.…”

“…Overall, these results, alongside those of other recent surveys (for example, Hansen et al, 2011;Bridges et al, 2012), indicate that the mobility of sand-size sediment may be relatively commonplace, if only occurring somewhat slowly across Mars. These results are significant additions to the understanding of aeolian transport pathways for Mars and offer data that can be compared with terrestrial analogues in which direct analysis of source-to-sink settings are made (see, for example, in this Special Issue: Hooper et al, 2012;Tirsch et al, 2012).…”

“…Hooper et al (2012) present one of the first detailed terrestrial analogue investigations into the classical sedimentological characterization of volcaniclastic sediments, and the associated geomorphological information of aeolian bedforms (coppice and falling dunes, ripples and sand streaks) for comparison with Mars. Hooper et al (2012) present one of the first detailed terrestrial analogue investigations into the classical sedimentological characterization of volcaniclastic sediments, and the associated geomorphological information of aeolian bedforms (coppice and falling dunes, ripples and sand streaks) for comparison with Mars.…”

“…The understanding of sediment source, distal and/or proximal, is a key issue for defining the development of bedforms of all sizes, the manner in which sediment load is chemically and physically altered in transport, the mechanisms of transport that may not be solely aeolian and how textural, granulometric and mineralogical signatures may be preserved in the transport of sediments from source-to-sink settings. Hooper et al (2012) present one of the first detailed terrestrial analogue investigations into the classical sedimentological characterization of volcaniclastic sediments, and the associated geomorphological information of aeolian bedforms (coppice and falling dunes, ripples and sand streaks) for comparison with Mars. The 566 M. A. BISHOP research conducted within the redistributed tephra deposits of Sunset Crater in northern Arizona offers a strong analogue baseline for comparison with like features on Mars, especially those made with the Mars Exploration Rovers (MERs) and the future datasets that will be derived from the Mars Science Laboratory (MSL) rover Curiosity.…”

Interpreting ambiguous bedforms to distinguish subaerial base surge from subaqueous density current deposits

“…Wind‐blown volcaniclastic deposits are typically fine to medium ash and very well sorted, lacking dense lapilli, blocks and very fine‐grained ash. An abundance of mixed of non‐volcanic detritus can exist, and generally, fragments are better‐rounded than those observed in pyroclastic density current deposits (Smith & Katzman, ; Valentine & Fisher, ; Hooper et al ., ). Wind‐blown dunes have migration and facies variations that do not radiate from a central point, for example a volcanic source (Valentine & Fisher, ).…”