Paleoclimate of the Little Ice Age to the Present in the Kankakee Valley of Illinois and Indiana, USA Based on 18O/16O Isotope Ratios of Freshwater Shells

The cooling associated with the Little Ice Age (LIA) had differential severity across the globe. Within the American Midwest, the local impacts of this cooling have not been established. Our purpose here is to determine its local effects and establish the impacts on the environment encountered at a seventeenth century Native American village in Illinois, USA. We obtained oxygen and carbon stable isotope ratios of freshwater mussel shells from this early seventeenth century site, occupied during one of the coldest periods of the LIA. These data were compared to the oxygen and carbon ratios of freshwater shells from a nineteenth century cabin as well as modern shells. Results demonstrate that shell stable oxygen isotopes capture environmental conditions at the three sites and suggest more arid conditions during the LIA and increased precipitation into the present. Findings also may capture the extensive alteration of the Kankakee region’s drainage between the late nineteenth and early twentieth centuries as well as contemporary global warming. Overall, this study illustrates the value of archaeological data to past and contemporary climate studies.