A multi-proxy limnologic record of rapid early-Holocene hydrologic change on the northern Great Plains, southwestern Saskatchewan, Canada

Clearwater Lake, Saskatchewan, is a relatively shallow, topographically closed, perennial lake cen trally located in the Palliser Triangle region of western Canada. Despite its present-day small size, Clearwater Lake is one of only a few lacustrine basins in this vast 400 000 km2 region of the northern Great Plains whose stratigraphic record extends to the early Holocene. Multiple proxy indicators are used to interpret the early-Holocene limnologic and hydrologic conditions in the basin. Changes in solute chemistry and concentration are reflected by siliceous microfossils and the endogenic and authigenic mineralogy of the sediment. The diatoms also provide evidence of fluctuations in water depth and water column stratification. Plant macrofossil assemblages, sediment texture and bedding features, and detrital mineralogy help to reconstruct drainage basin conditions and water level changes. Stable O-nd C-isotopic composition of inorganically precipitated, endo genic carbonate minerals provide insight into the hydrologic budget of the basin and the residence time of the water. An early-Holocene shallow, clastic-dominated, freshwater lake, probably surrounded by boreal forest type vegetation, was followed by a mesosaline to hypersaline phase between 9800 and 8600 BP. A fresh to hyposaline lake with an open basin hydrology returned after 8600 BP and persisted until at least 6600 BP except for a short episode of higher salinity, closed-basin evaporitic conditions about 8200–7700 BP.