HOLOCENE PALEOCLIMATE RECORD OF NORTHERN IOWA RECORDED IN FLOWSTONE

During the mid-Holocene, the Midwest was subject to a prolonged interval of warm and dry climate (7-5 ka) which interrupted the cool, humid climate of much of the epoch. This warm interval was most likely the result of orbital climate forcing and is evidenced by changes in stratigraphy, vegetation, and isotopic data. This project aims to use stable isotope data from an Iowa flowstone to corroborate the timings and magnitude of this disturbance with previous studies. The flowstone, of aragonitic composition, was collected from a quarry 6 km south of Waterloo, Iowa, within the Devonian Cedar Valley formation. The sample was prepared at Augustana College, where a circular saw was used to cut the flowstone into thin slices from which aragonite powder could be collected at 1 mm intervals across multiple layers of precipitated aragonite. Mass spectroscopy will be performed on the samples at Iowa State University to produce δ­18O and δ13­C values which under equilibrium conditions reflect temperature and precipitation conditions during the time of formation. Additionally, ICP-MS will be performed on additional aragonite samples to perform U-Th dating, which will allow the aragonite sequences to be dated with a high degree of temporal resolution. The results of this study will then be compared to other speleothem studies from the same region.