Collaborative Proposal: Development and calibration of the oxygen isotope systematics of small terrestrial gastropods

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Land snails are one of the most common fossils in the terrestrial geologic record of North America. Their shells are composed of calcium carbonate and the oxygen isotopic composition of their shells record climatic conditions during growth. Therefore, the oxygen isotopic composition of land snails has the potential to reconstruct past climates on broad spatial and temporal scales. To date, however, there is a little understanding on the kinds of climatic information that can be inferred from the snails, and therefore, their current use as paleoclimatic archives is limited. This proposal will develop, test, and calibrate the oxygen isotope systematics of small land snails for use as a paleoclimatic proxy in terrestrial settings across North America. The modern calibration of this proxy will benefit society through the development of a terrestrial paleoclimatic proxy that is capable of reconstructing past climate over broad spatial and temporal scales and also will improve our understanding of the taxonomic diversity and spatial distribution of land snails, a fauna that is decreasing at an alarming rate globally. This project will teach and train future scientists, from high school to PhD candidates, integrate scientists from multiple fields (paleontology, biology, Quaternary geology), and broaden the participation of diverse and underrepresented groups. Dissemination of results will include a diverse audience (specialists and general public), in English and Spanish to reach the Hispanic community in USA and elsewhere. This project will establish linkages between underrepresented groups and STEM disciplines at research-intensive universities. To calibrate the oxygen isotope systematics of modern land snails in North America, investigators will analyze the oxygen isotope composition of approximately 1,000 shell samples from modern snails collected along two selected transects that cross North America from southern Texas to Canada. They will identify the primary climatic controls on shell ä18O values by quantifying the relation between shell ä18O and relevant climatic variables (temperature, ä18O of precipitation, precipitation amount, relative humidity) using an evaporative steady-state flux balance-mixing model developed for land snails. Researchers hypothesize that: (1) the oxygen isotope composition of small land snails in temperate environments (latitudes of 26 to 48 degrees N) primarily will reflect the oxygen isotope composition of precipitation, and therefore can be used to infer past changes in precipitation oxygen isotope values; and (2) shell oxygen isotope values of snails living in arid to semi-arid environments will yield higher values than predicted because of low relative humidity values. After calibration of the oxygen isotope systematics for living specimens, investigators will conduct two case studies to determine how well the oxygen isotope values of small snails track the oxygen isotope records of speleothems or other proxy records. The proposed work will allow better quantification of past climate change over broad areas of North America, and from many different types of deposits.