Overview of the oxygen isotope systematics of land snails from North America

摘要

Continental paleoclimate proxies with near-global coverage are rare. Land snail delta O-18 is one of the few proxies abundant in Quaternary sediments ranging from the tropics to the high Arctic tundra. However, its application in paleoclimatology remains difficult, attributable in part to limitations in published calibration studies. Here we present shell delta O-18 of modern small (<10 mm) snails across North America, from Florida (30 degrees N) to Manitoba (58 degrees N), to examine the main climatic controls on shell delta O-18 at a coarse scale. This transect is augmented by published delta O-18 values, which expand our coverage from Jamaica (18 degrees N) to Alaska (64 degrees N). Results indicate that shell delta O-18 primarily tracks the average annual precipitation delta O-18. Shell delta O-18 increases 0.5-0.7 parts per thousand for every 1 parts per thousand increase in precipitation delta O-18, and 0.3-0.7 parts per thousand for every 1 degrees C increase in temperature. These relationships hold true when all taxa are included regardless of body size (ranging from 1.6 to 58 mm), ecology (herbivores, omnivores, and carnivores), or behavior (variable seasonal active periods and mobility habits). Future isotopic investigations should include calibration studies in tropical and high-latitude settings, arid environments, and along altitudinal gradients to test if the near linear relationship between shell and meteoric precipitation delta O-18 observed on a continental scale remains significant.