MP9: Chapter 4: Georadar Characterization of Vertebrate Burrows Across a Gypsum Dunefield
by I.V. Buynevich, A.P.K. Bentley, L.A. Wiest, D. Bustos and D.J. Jerolmack.
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This chapter is from GAC's Miscellaneous Publication 9: "Ichnology: Papers from Ichnia III" editted by Dr. Duncan McIlroy. To purchase the entire book on disc, please see the Miscellaneous Publications section of our bookstore at http://www.gac.ca/publications/view_pub.php?id=262.
In the worlds largest gypsum dunefield (White Sands National Monument, New Mexico), modern vertebrate burrows occur in a variety of sub-environments, which include (in a downwind direction): vegetation-anchored coppice dunes or bare surfaces adjacent to barchans, sparsely vegetated transitional interdunes, densely vegetated blowout sections of parabolic dunes, and raised margins of ephemeral playa lakes. The primary semi-fossorial producers of 7‒20-cm-wide sub-horizontal to steeply inclined excavations are desert kit fox, badger, burrowing owl, and several species of kangaroo rats. In most interdunes, the excavation depth is limited by a relatively shallow (~1 m) water table. To assess, in a non-invasive manner, the subsurface extent and geophysical signal scattering effect of active burrows, continuous high-resolution images were obtained using 500 and 800 MHz ground-penetrating radar (GPR) antennas. In radargrams, burrows appear as hyperbolic (point-source) diffractions that have apparent diameters ranging from 12‒25 cm (due to actual size increase or any deviation from an attitude normal to the transmitted GPR trace). Most shafts and tunnels truncate major bounding discontinuities, although the potential for recognizing and mapping the infilled and buried voids is limited by low dielectric contrast within lithologically homogeneous eolian deposits. Localized changes in bedding geometry and chemical processes that accentuate burrow walls may compensate for this limitation. This study demonstrates the viability of GPR technique in characterizing bioturbation structures in wet eolian systems.
Geological Association of Canada
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