Elsevier

Geomorphology

Volume 105, Issues 1–2, 1 April 2009, Pages 59-66
Geomorphology

Abrasion control on dune colour: Muleshoe Dunes, SW USA

https://doi.org/10.1016/j.geomorph.2008.01.019Get rights and content

Abstract

The Muleshoe Dunes, an east–west trending dunefield on the border separating Texas and New Mexico, consist of two distinct components: a white (carbonate rich) component and an overlying pink (quartz rich) component. The pink component exhibits significant spatial variation in redness. The reddest sands, in the western part of the dunefield, decrease in redness towards the east. This gradient is thought to result from abrasion of an iron-rich, red clay coating as the sediments were transported eastward by Late Quaternary aeolian processes. The effects of aeolian abrasion on the spectral signature and surface texture of the sediments were examined using laboratory abrasion experiments. Changes in spectral reflectance of abrasion samples from the laboratory were compared to field samples that were abraded naturally because of sediment transport. The changes resulting from increased time of abrasion are similar to those observed with increased distance downwind in the dunefield. These results suggest that downwind abrasion can explain the pattern of dune colour in the Muleshoe Dunes, although this does not preclude other possible causes.

Introduction

Many continental dunefields exhibit a gradient of redness caused by an iron-rich material coating the surface of sand grains or by differing sediment sources. Redness gradients have been quantified using spectral reflectance properties along field transects in the Simpson dunefield, central Australia (Bullard and White, 2002) and mapped successfully over large areas such as the Namib dunefield, southwest Namibia, using remote sensing (White et al., 1997, White et al., 2007). This paper examines the changes in spectral reflectance properties that result from laboratory abrasion of a sample of sand from the upwind end of the Muleshoe Dunes, a small dunefield in SW USA, and compares the results with the redness gradient observed in the field. When calibrated using field or laboratory methods, remote sensing can be used to map the spatial characteristics of dunefields—such as landform distribution (Quarmby et al., 1989, Pease et al., 1999) and the geochemical properties of sediments (El-Baz, 1978, White et al., 2001, Ben-Dor et al., 2006). Bullard and White (2005) suggested that the potential exists to use remote sensing to map sedimentological processes operating in dunefields, such as aeolian abrasion, and this paper explores this concept further.

A large part of the Southern High Plains (Llano Estacado) of northwestern Texas and eastern New Mexico is covered by extensive (> 10 000 km2), stabilized deposits of aeolian sand. Within this region, the Muleshoe Dunes (Fig. 1) are a west–east trending belt of sand that consists of a series of individual dune fields separated by sand sheets or sand free areas (Holliday, 2001). The activity of these dunefields over the late Holocene and into historical times, and the current and potential future status has received a significant amount of research (Ahlbrandt et al., 1983, Madole, 1994, Forman et al., 1995, Muhs and Holliday, 1995). Other work has focussed on the provenance of these sands (Muhs et al., 1996, Holliday, 1997). Detailed geochemical analyses point to the underlying Blackwater Draw Formation, a vast (> 100 000 km2) sheet of Quaternary aeolian sands up to 27 m in thickness, as a source of the Muleshoe dune sands (Muhs and Holliday, 2001). The dunes follow the dry valley of the Blackwater Draw, a tributary of the Brazos River. The most common dune forms are simple parabolic dunes that are 200–400 m long, associated with blowouts, coppice dunes, barchan dunes and fence row dunes (historic dunes formed along field boundaries). The orientation of the dunes indicates palaeowinds dominantly from the west, which agrees with resultant drift directions derived from modern meteorological data during winter and spring when vegetation cover is at a minimum (Muhs and Holliday, 2001). The westerly wind direction may result, in part, from funnelling winds through the Portales Valley, a re-entrant in the western High Plains escarpment (Holliday, 2001). Radiocarbon dating of buried soils indicates that the Muleshoe Dunes accumulated in several stages: after 1300 cal yr B.P., after 750–670 cal yr B.P., after 500 cal yr B.P., and during the last 200 years (Holliday, 2001). Stabilization of the Muleshoe Dunes occurs because of vegetation cover, thus, the dunes are supply-limited but can be reactivated by minor droughts (Muhs and Holliday, 2001).

The Muleshoe Dunes show considerable spatial variability of colour, carbonate content, granulometry and clay content (Muhs and Holliday, 2001). Two types of dunes are recognised on the basis of carbonate content; pink dunes of reddish hues (5YR or 7.5YR) that are largely free of carbonates; and overlying white dunes of light grey and light brown hues (10YR 6/2, 10YR 6/3, 10YR 6/4 and 10YR 7/2) that contain varying amounts of carbonate. The pink dunes show a systematic trend in colour across the Muleshoe Dunes, strong enough to be detected by Munsell Soil Colour determination (Muhs and Holliday, 2001), despite the low sensitivity and poor reproducibility of this technique (Anton and Ince, 1986, Bullard and White, 2002). To the west, the pink dunes have mostly reddish 5YR hues and become less red (10YR) towards the east (the downwind direction). This observation is contrary to the pattern found in other dune fields where dunes usually become redder downwind (El-Baz, 1978, Walker, 1979, Gardner and Pye, 1981, Lancaster, 1989, Bullard and White, 2002) and, together with the decreasing clay content downwind, is interpreted by Muhs and Holliday (2001) as resulting from increasing downwind abrasion and the progressive removal of red-pigmenting clay coatings from the sand grains.

This paper seeks to examine the hypothesis proposed by Muhs and Holliday (2001) that the pattern of decreasing dune redness downwind, evident in the pink dunes, results from abrasion. The spectral reflectance properties of samples abraded in the laboratory are compared to samples collected at different locations in the Muleshoe Dunes. Comparison of the surface textures of laboratory abraded samples with those of samples from different locations in the Muleshoe Dunes are used to look for further evidence linking the variations in dune colour to aeolian abrasion.

Section snippets

Laboratory abrasion

A sample of red sand was collected from the western end of the Muleshoe Dunes (34.4151°N, 103.6169667°W). The sediment was abraded using an aeolian abrasion chamber of the same design as that used by Whalley et al. (1987). The sample was placed in the bottom of a large glass ‘test-tube’ abrasion chamber and the grains agitated by an air stream. Fine particles raised into suspension within the chamber are trapped by an electrostatic precipitator operating at 5 kV with a trapping efficiency of

Results

The raw spectra (Fig. 2A) show only one distinct absorption feature over the range 400–1050 nm This Fe3+–O charge transfer band is located in the ultraviolet part of the electromagnetic spectrum. It has a well resolved absorption edge tailing into the visible, causing a fall-off in reflectance short of 550 nm (Hunt et al., 1971) and resulting in a strong minima in the hull differences between 500 and 530 nm (Fig. 2B). Charge transfers occur where the absorption of a photon causes an electron to

Discussion

On the basis of downwind trends in granulometry and clay content, Muhs and Holliday (2001) hypothesised that the redness gradient evident in the pink Muleshoe Dunes is a function of aeolian abrasion processes during sand transport. If we assume that Muleshoe Dune sand colour is entirely a function of abrasion resulting from eastward transport, and that the empirical relationships derived from our field data and our laboratory simulations are an appropriate representation of the abrasion

Conclusions

The pink Muleshoe Dunes in SW USA show a marked pattern of decreasing redness in an easterly direction (downwind). The colour variation likely results from gradually varying concentrations of Fe-oxide coatings on the sand grains from west to east. The results of this research demonstrate that the decrease in dune redness may be explained by removal of the Fe-oxide coating by aeolian abrasion, similar to that simulated successfully in the laboratory. The resulting patterns in spectral redness

Acknowledgements

The authors would like to thank Dan Muhs (US Geological Survey) and Vance Holliday (University of Wisconsin) for useful discussions and making available their geochemical data, Tom Gill (University of Texas at El Paso) for all his help with logistics and collection of field data, Christa Pudmenzky (Griffith University, Australia) for her assistance with the laboratory abrasion experiments and Jeff Settle (NERC-ESSC) for help with data analysis. This research was funded by The Leverhulme Trust

References (48)

  • WhiteK. et al.

    Mapping the iron oxide content of dune sands, Namibia, using Landsat Thematic Mapper data

    Remote Sensing of Environment

    (1997)
  • WhiteK. et al.

    Spectral properties, iron oxide content and provenance of Namib dune sands

    Geomorphology

    (2007)
  • AntonD. et al.

    A study of sand colour and maturity in Saudi Arabia

    Zeitschrift für Geomorphologie, N. F.

    (1986)
  • BlountG. et al.

    Regional aeolian dynamics and sand mixing in the Gran Desierto: evidence from Landsat Thematic Mapper images

    Journal of Geophysical Research

    (1990)
  • BullardJ.E. et al.

    Quantifying iron oxide coatings on dune sands using spectrometric measurements: an example from the Simpson-Strzelecki Desert, Australia

    Journal of Geophysical Research

    (2002)
  • BullardJ.E. et al.

    Dust production and the release of iron oxides resulting from the aeolian abrasion of natural dune sands

    Earth Surface Processes and Landforms

    (2005)
  • BullardJ.E. et al.

    Aeolian abrasion and modes of fine particle production from natural red dune sands: an experimental study

    Sedimentology

    (2004)
  • ClarkR.N.

    Spectral properties of mixtures of montmorillonite and dark carbon grains: implications for remote sensing minerals containing chemically and physically adsorbed water

    Journal of Geophysical Research

    (1983)
  • ClarkR.N.

    Spectroscopy of rocks and minerals, and principles of spectroscopy

  • ClarkR.N. et al.

    Spectral properties of ice-particulate mixtures and implications for remote sensing

    Journal of Geophysical Research

    (1984)
  • ClarkR.N. et al.

    Reflectance spectroscopy: quantitative analysis techniques for remote sensing applications

    Journal of Geophysical Research

    (1984)
  • El-BazF.

    The meaning of desert color in Earth orbital photographs

    Photogrammetric Engineering and Remote Sensing

    (1978)
  • GardnerR. et al.

    Nature, origin and palaeoenvironmental significance of red coastal and desert dune sands

    Progress in Physical Geography

    (1981)
  • Geophysical and Environmental Research Corp.

    GER 3700 User Manual Release 2.1

    (1999)
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