Midwest North American full glacial paleohydrology from fresh water ostracodes: Comparison of Clementsian and Gleasonian methodologies

Here we explore the results and differences of two methods for reconstructing climatic and paleohydrological conditions from two sites in central North America during the Last Glacial Maximum. The Clementsian assemblage-based Mutual Climate Range (MCR) and Gleasonian species-range-based Mutual Ostracod Temperature Range (MOTR) methods are featured. We use autecological data from the North American Ostracode Database (NACODe) that includes water chemistry, physical data, location, and ambient climatic information from 7328 sites and the presence of 108 ostracode species. Reconstructions of last glacial average temperatures for January and July means, average mean annual temperature, mean total annual precipitation, and total dissolved solids of the host water are provided for records at Bellefontaine Quarry (Missouri) and Prides Creek (Indiana). The successions collectively date from about 25,100 to 18,300 cal yr BP. Our novel python program enables MCR calculations with results that fall within the envelope of values determined by MOTR. The program enables the user to determine the critical number of species that yield data less influenced by data structure and tending toward redundant but representative environmental and hydrochemical paleo-conditions. Data from sites with common species below the critical number are controlled by the biogeographic structure of NACODe; above the critical number, analog data reflect physiochemical attributes operating under a range of climatic conditions. The greater mean species richness of the Prides Creek record (x‾ = 12) compared to Bellefontaine (x‾ = 6) results in smoother profiles of mean Clementsian Mutual Climate Range values. We have modified an analog selection and ranking routine by favoring sites with sensitive species as defined by an environmental tolerance index. For average mean July temperature and mean total dissolved solids, the Prides Creek MCR-ETI profiles have approximately the same value as average values given by the Gleasonian Mutual Ostracod Temperature Range procedure. For average mean annual temperature and average mean January temperatures, MCR-ETI values plot on the cooler side of the MOTR envelopes, but still entirely within the envelope. For both records, mean total annual precipitation MCR-ETI profiles are on the arid side of the Gleasonian envelope. These results likely reflect the location of analog sites with the largest number of environmentally sensitive ostracodes and matching species located in southern Minnesota and Wisconsin at or near the edge of the prairie-forest transition where potential evapotranspiration is about equal to mean annual precipitation.