THE NEBRASKA SAND HILLS - DROUGHT VARIATION AND LANDSCAPE STABILITY IN THE LATE-HOLOCENE

The reconstruction of drought variability and associated landscape change in the Sand Hills of Nebraska is examined at decadal to multi-decadal resolution during the last 4000 years. This research will test whether recurring drought events exhibited a distinctive spatial pattern and it will provide insight into the temporal evolution of these desertification episodes. Diatom assemblages are used to reconstruct paleo-lake levels and track changes in lake salinity and chemistry. The diatom record will be compared to other proxies, such as bulk sediment chemistry and grain-size analysis, to reconstruct regional moisture balance fluctuations related to climate variability. OSL dates obtained from sand layers interspersed in the peat and lake sediments will be used in conjunction with 14C-derived ages of organic sediments in order to generate a reasonable age model for the sediment sequence. Finally changes in moisture inferred from the lake record will be compared with the upland dune record to evaluate the climatic context associated with major dune destabilization.