Investigating the post-Mazama sedimentary record in lakes of western Montana

Mount Mazama was a volcano located at current day Crater Lake in southwestern Oregon. It erupted 7,630 +/- 80 cal yr BP. The eruption was enormous and forced large volumes of ash into the atmosphere where it subsequently settled out to become part of the sedimentary record in lake basins across much of the Pacific Northwest, including in northwestern Montana. The purpose of this project is to examine the post- Mazama record of sedimentation from two lakes in western Montana. The two lakes are Lake Mary Ronan and Flathead Lake. The Mazama tephra is very well preserved and little disturbed in both of these lakes. The hypothesis that I seek to test is that the massive eruption of Mount Mazama produced a sustained period of drought in northwestern Montana immediately following the eruption. Independent analyses from Flathead Lake suggest that this drought resulted in a drawdown that was sufficient enough to produce and develop a soil in Lake Mary Ronan. High resolution imaging of the cores, sedimentary grain size changes analysis, total inorganic carbon content (TIC analysis), to test this hypothesis. The grain size analysis should show an increase in the size of the sediment grains and the TIC analysis should show an increase in total inorganic carbon after the Mazama tephra was deposited. Preliminary X-ray analysis of Lake Mary Ronan sediment records suggest that soil profile fabrics developed shortly after the deposition of the ash. This topic is of interest because it investigates the effects that large volcanic eruptions can have on climate