THE RECORD OF HOLOCENE DUNE DEPOSITION – FROM DEGLACIATION TO PRESENT – NORTHERN GREAT PLAINS, CANADA

The Bigstick and Seward sand hills are possibly two of the oldest dune fields in Saskatchewan, Canada. In accordance with the deglacial history of southern Canada, these dune fields have an estimated maximum limiting age on the order of 15.3 ka. As with other dune fields on the Canadian prairies, the source materials for these dunes are proglacial outwash sands, having received no additional input of sediment during the Holocene. Thus, Holocene construction of dunes here may be more closely tied to changes in climate and vegetation cover than other Great Plains dune fields. However, aeolian landscape reconstructions within the southern Canadian prairies have been temporally constrained to more recent periods, as older aeolian sands are either reworked or covered by younger deposits. This noted, we present new evidence from sediment cores in shallow lacustrine basins and interdune aeolian sand sheet areas from the Bigstick and Seward sand hills that retain longer temporal records of Holocene aeolian sand deposition. We identify several major periods of aeolian sand deposition since deglaciation, interpreted as comparatively arid dune-forming intervals, interspersed by lacustrine and soil-forming episodes interpreted as more humid intervals. Dune sand deposition is recorded during the late Pleistocene between 14.2 and 13 ka, in the early-to-mid Holocene between about 10.0 and 6.7 ka, the Holocene from about 4.2 and 2.3 ka, and most recently from 340 years to present. Although analytical uncertainties in the ages are large (typically on the order of ±14% at one standard deviation), it is clear that specific time periods of dune construction have occurred, and that the maximum ages of dune sand deposition are comparable to the timing of deglaciation and drainage of pro-glacial lakes in southern Saskatchewan.