A postglacial record of climate change from East Crooked Lake and Tofte Lake, Minnesota.

Abstract

The postglacial Holocene climate history of Minnesota is characterized by a cool postglacial period beginning about 10 ka and lasting until about 8 ka when dryer conditions ushered in a Prairie Period which lasted until about 4 ka at which time moisture increased. From about 4 ka to the present climate conditions have remained relatively stable. This history of Minnesota climate has been observed by Dean and colleagues in numerous studies at Elk Lake, Minnesota. In these studies the researchers looked at pollen, geochemistry, diatoms, magnetic properties, and isotopes. This study uses sediment cores from nearby East Crooked Lake to see if scanning X-ray fluorescence results are comparable to classic inorganic geochemistry results from Dean at Elk Lake. A sediment core from Tofte Lake near Ely, MN is also compared to see if the results from Elk Lake and East Crooked Lake are regional in extent. The results confirm that scanning XRF is comparable to the classic, time consuming geochemistry methods used by Dean at Elk Lake and that the postglacial Holocene history recorded at Elk Lake was also recorded at East Crooked Lake. The timing of events at Elk Lake and East Crooked Lake are adjusted to correlate with the more accurate dating of events at Steel Lake, MN. The findings do not support that the climate events at Elk Lake and East Crooked Lake are regional in their extent to Tofte Lake. Tofte Lake did not experience a dryer Prairie Period.