Calibrating grass phytolith assemblages in climatic terms: Application to late Pleistocene assemblages from Kansas and Nebraska

The use of modern phytolith assemblages for the interpretation of fossil phytolith assemblages demonstrates the utility of phytolith analysis in reconstructing grassland vegetation and climate in the Great Plains of North America. The modern data presented are the typical (average) assemblages for 34 modern localities taken throughout the Great Plains. Modern assemblage variability across the region is substantial. This variability shows a coherent geographical pattern consistent with modern grassland composition. These modern phytolith assemblages are calibrated in terms of modern climate data: specifically July mean temperature. Seven fossil assemblages from three late Pleistocene localities in the central Great Plains are presented. Two alternative phytolith-temperature regression models are applied to these fossil assemblages to estimate paleo-temperature. Resulting estimates are consistent with other efforts to calculate late Pleistocene temperature departures in the region (ca. −8.0 to −7.0°C). The fossil data also show rapid change in grassland composition and climate during the Pleistocene-Holocene transition. These results demonstrate how phytolith analysis can complement, or substitute for, pollen analysis in the Great Plains of North America.