An Assessment of Prairie Mound Origin Theories
at University of Arkansas Experimental Farms

Conclusions

            The evidence from this study is equivocal in regard to the seismic shaking and fossorial rodent hypotheses, except to confirm a shallowly buried hard or impenetrable surface.  The lack of such a surface would have argued strongly against both theories as they are currently articulated, because they both demand that such a feature be present.  The presence of such a surface merely fails to discredit these hypotheses for mounds in this area.

            Sediment size analysis in this report argues strongly against the hypotheses of aeolian or fluvial deposition.  The mound bases occur at a lower level than the surface under which the textural B horizon formed, and parent material within and beneath the mounds is identical.

            Soil and sediment evidence from this study lends weak support to a fluvial or aeolian erosion hypothesis.  Uniformity of parent material and the contouring of soil horizons are consistent with such origins. The presence of a shallowly buried surface impenetrable to water also lends support to a fluvial erosion origin.

            Subsequent studies of prairie mounds in this region might further test these hypotheses through bulk density sampling and thin section analysis.  Evidence of accumulation of larger clasts at a depth consistent with the maximum depth of rodent burrowing would lend support to the fossorial rodent hypothesis.  Lack of such accumulation in mounds that contain larger clasts would serve to largely discredit this hypothesis.  Evidence of horizontal stratigraphy consistent between mounds would indicate that they are relics of a former, higher ground surface, and thus lend support to an erosional origin hypothesis.

            Further studies of mound orientation and landscape position might help evaluate the fluvial and aeolian erosion hypotheses.  Uniform mound orientations in a wide area not conforming to water flow direction would lend support to an aeolian erosion origin, as would the presence of mounds above present or former floodplains.  Mound orientations consistent with water flow direction over a wide area would lend further support to a fluvial erosion origin. 

Acknowledgments

            I would like to thank Dr. John Dixon, Dr. Margaret Guccione, and Dr. Marvin Kay for their insightful comments and editing of this paper.  Dr. Guccione, especially, offered much support for the project.  The Giddings-rig core machine and soils laboratory were graciously provided by the University of Arkansas.  Michelle Berg Vogel served as field crew and offered, as always, superlative advice.