FORMATION FOR GREEN LAKE AND ROUND LAKE, GREEN LAKES STATE PARK NEW YORK: TESTING THE PLUNGE POOL MODEL

Green Lakes State Park in Fayetteville, New York contains two small but very deep meromictic lakes; Green Lake and Round Lake. Short sediment cores from Green Lake contain paleoclimate records through the later part of the Holocene (circa 2,500 years BP). There are two main theories for the formation of these lakes based on their size and shape: erosion by glacial melt water forming a waterfall plunge pool, or dissolution of soluble bedrock and collapse of a sinkhole. Both models could explain the depth and morphology of the basins but the plunge pool model only allows for lake sedimentation since the end of the last glaciation, while the sinkhole model is not limited in time as a post-Last Glacial Maximum feature. If proven to be sinkholes, Green Lake and Round Lake may contain a much older record of paleoclimate than previously considered.

The focus of this study is to test the plausibility of the plunge pool formation mechanism based on a recently published MATLAB modeling approach. A critical variable in testing the plunge pool formation mechanism is the depth of the plunge pool from its base to the downstream spill point. This variable provides a first order control on the erosive power of falling water at the bottom of the pool. If this depth is found to be too great then the plunge pool mechanism can be considered invalid. In order to determine plunge pool depth, the elevation of bedrock at the spill point relative to the depth of Round Lake needs to be determined. The depth of Round Lake is known from previous bathymetric surveys. The elevation of bedrock at the spill point has been determined using the integration of newly collected ground penetrating radar profiles, mapping of sediment fill above bedrock in Green Lake with a submersible ROV, and previous sediment cores collected between the lakes.