It was great to help out Dr. Tim Fisher (University of Toledo) in this effort (the full publication is here). Dr. Fisher was vacationing in Georgian Bay on Lake Huron when he discovered a stump rooted ~0.5 below the historical low of 1985. This low stand based on radiocarbon and tree-ring analysis occurred during the late decades of the 1600s. Since Lakes Michigan and Huron are joined at the straits of Mackinaw we can infer that this drop was basin wide. Such a drop today would significantly affect the shipping and shoreline infrastructure of these international water ways.
Figure 1. Map showing the location of the stump in Georgian Bay.
Figure 2. Photographs of the in-place stump.
Figure 3. Dating of the stump is critical and the figure above shows the wiggle-matching of a series of radiocarbon ages with the help of a tree ring sequence. Radiocarbon ages matched to the radiocarbon calibration curve allows for a unique solution to the dating placing the age of tree growth into the late 1600s.
The late 1600s is a fascinating interval in Earth history and has been associated with large-scale changes in the ocean – atmosphere system worldwide. Work by colleagues in Scotland have linked this