Radiocarbon dating loess deposits in the Mississippi Valley using terrestrial gastropod shells (Polygyridae, Helicinidae, and Discidae)

Authors

Jeffrey S. Pigati, U.S. Geological Survey, Denver Federal CenterFollow
John McGeehin, US Geological Survey
Daniel R. Muhs, U.S. Geological SurveyFollow
David A. Grimley, Illinois State Geological Survey, University of Illinois
Jeffrey C. Nekola, University of New MexicoFollow

Document Type

Article

Date of this Version

2014

Citation

Aeolian Research 16 (2015) 25–33

doi 10.1016/j.aeolia.2014.10.005

Comments

US government work

Abstract

Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that are accurate to within a few hundred years. In contrast, shells of the genus Mesodon (Mesodon elevatus and Mesodon zaletus) contain significant and variable amounts of old carbon, yielding ages that are up to a couple thousand ¹⁴C years too old. Although terrestrial gastropod shells have tremendous potential for ¹⁴C dating loess deposits throughout North America,weacknowledge that accuracy to within a few hundred years may not be sufficient for those interested in developing high-resolution loess chronologies. Even with this limitation, however, ¹⁴C dating of terrestrial gastropod shells present in Mississippi Valley loess deposits may prove useful for researchers interested in processes that took place over multi-millennial timescales or in differentiating stratigraphic units that have significantly different ages but similar physical and geochemical properties. The results presented here may also be useful to researchers studying loess deposits outside North America that contain similar gastropod taxa.