| There is public interest in obtaining long drought records for the northern Great Plains. However, little of such information is available for the northeastern part of this region, especially for the late-glacial and early postglacial. This study reconstructs the vegetation and climate history of the northeastern Great Plains from about 11,500 14C yr B.P. to approximately 6000 14C yr B.P. This study is based upon the analysis of 126 pollen and 371 macrofossil samples collected from four sites in southeastern North Dakota and adjacent parts of South Dakota and Minnesota. These samples are interpreted in relation to site lithostratigraphies and in association with 25 radiocarbon ages.; The paleoclimate signal for the northeastern Great Plains appears to be time- and space-transgressive, reflecting differential plant responses to the legacies of deglaciation (such as residual glacial meltwater). In the central part of this area, white spruce trees and prairie herbs colonized the Glaciated Till Plain (the Wendel Site) as early as 11,500 14C yr B.P., suggesting a climate slightly cooler than modern and possibly somewhat drier than previously thought. On the Missouri Coteau upland to the west (Coldwater Lake), delay in the establishment of an open white spruce woodland until 10,800 14C yr B.P. is attributed to lags in the formation of a depositional environment.; The replacement of spruce woodland by grassland at the Wendel Site indicates that this warming/drying trend became more pronounced at about 11,000 14C yr B.P. This paleoclimatic interpretation is supported by the shift to a parkland of deciduous trees and prairie herbs on the Missouri Coteau at about 10,600 14C yr B.P., which persisted until at least 10,200 14C yr B.P. A deciduous parkland also colonized the temporarily abandoned southern basin of glacial Lake Agassiz, (Trollwood Park Site) from 10,230 to 9900 14C yr B.P. The deciduous parkland phase likely reflects localized high soil-moisture conditions. Grassland subsequently became widespread throughout the region, appearing later (9400 14C yr B.P.) in the southern Agassiz basin (Big Stone Lake). This study indicates that the onset of peak aridity in the northeastern Great Plains occurred between 9500 and 8000 14C yr B.P. |
