Early-Holocene limnological and climatic variability in the Northern Great Plains

Information on the timing and direction of climatic and environmental change on a millennial scale exists for many regions of North America, whereas little is known about decadal-to centennial-scale variability. Here we present a high-resolution analysis of diatom-inferred salinity from a site in the Northern Great Plains to reconstruct multidecadal-and centennial-scale climatic patterns during the early Holocene. The diatominferred salinity indicates a transition from fresh to highly saline conditions between c. 13 400 and 7700 cal. yr BP, which suggests a major shift in climate from wet to dry conditions. The overall trend toward increasing salinity is interrupted by several freshwater intervals between c. 9800 and 7950 cal. yr BP, which may be the result of an increase in the frequency of monsoonal flow from the Gulf of Mexico. The early Holocene is considered to be a time of rapid change in climate and vegetation within the Holocene. Although rates of change in the Moon Lake diatom assemblages were high during parts of the early Holocene, in general the rate of change was as great or greater during the last two millennia. This finding may be the result of a generally directional change in climate in the early Holocene, in contrast to shorter-term fluctuations and little directionality in the late Holocene.