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Aeolian Dust Captured on Isolated Surfaces along a Transect from the Mojave Desert to the Colorado Plateau, USA

Goals

• Examine the causes of local to regional variations in texture and composition of arid-land soils with respect to past and modern dust inputs that may have varied due to changes in climate and dust sources.
• Investigate the possibility that some dust in Colorado Plateau soils originated from sources in the Mojave Desert.

Relevance

This study centers on the role of dust with respect to nutrient inputs and influence on hydrologic properties of soil. As such, conditions of dust emission, dust sources, and dust flux under variable climatic and land-use histories bear on interrelations between landscape evolution and ecosystem dynamics.

Background

In a previous study, aeolian dust was identified in fine-grained sediment captured in small depressions (potholes) on the central Colorado Plateau (Reynolds et al., 2001). Primary evidence for the aeolian origin for dust in the pothole sediments was the presence of detrital magnetite, which yielded moderately high magnetic susceptibility (MS). Rocks in which the potholes formed were devoid of magnetite and yield negligible MS values. Physical and chemical properties of dust in these potholes suggested dust sources outside the Colorado Plateau. For example, a high proportion of the silt fraction consists of <10 µm particles that are characteristic of far-traveled dust, and the content of magnetite and trace elements implied that some dust originated in geologic terrain characterized by felsic igneous rocks, such as the Mojave Desert of southeastern California (Reynolds et al., 2001).

Strategy

Following the strategy of Reynolds et al. (2001), we collected samples from potholes on high, isolated surfaces, developed mostly on Jurassic aeolian sandstone, along a transect from the central Mojave Desert northeast to the original study area on the central Colorado Plateau. Initially, physical and chemical parameters of the silt- and clay-size fraction were compared with those of associated bedrock to confirm the presence of aeolian dust. In addition, the spatial distributions of geochemical and mineralogic parameters in the pothole sediment were examined for regional trends along the southwest-to-northeast transect. If found, such trends might reveal some contribution of Mojave dust sources to fine-grained sediment on the Colorado Plateau.

Conclusions

• Composition and texture of fine-grained sediment in potholes on isolated surfaces are consistent with sources of dust in Colorado Plateau soils from arid regions to the west.
• Ecosystem dynamics on the Colorado Plateau are influenced by surficial processes in distant regions, for example the Mojave Desert.
• Aeolian dust can strongly influence soil geochemistry over large areas of the southwestern U.S.

References

Belnap, J. and J. Gardner. 1993. Soil microstructure in soils of the Colorado Plateau: The role of the cyanobacterium Microcoleus vaginitus. Great Basin Naturalist 53:89-95.

Goudie, A.S. 1978. Dust storms and their geomorphological implications. Journal of Arid Environments 1:291-311.

Reynolds, R., J. Belnap, M. Reheis, P. Lamothe, and F. Luiszer. 2001. Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source. Proceedings of the National Academy of Sciences 98:7123-7127.

Yaalon, D.H., and E. Ganor. 1973. The influence of dust on soils during the Quaternary. Soil Science 116:146-155.

For more information, contact Harland Goldstein.