ELUCIDATING NATURAL TRENDS AND PATTERNS IN WATER AND SEDIMENT CONVEYANCE BETWEEN LAKES HURON AND ERIE IN THE LAURENTIAN GREAT LAKES DURING THE LATE HOLOCENE

One of the most important connections in the Laurentian Great Lakes (LGL) is between lakes Huron and Erie that has naturally linked the upper (Superior and Michigan-Huron) and lower (Eire and Ontario) LGLs for many millennia. Today this connection is the only remaining section in the entire Great Lakes - St. Laurentian Seaway System that does not have locks or regulation structures. An investigation by the International Upper Great Lakes Study Board (2009, 2012) recommended that remedial measures in the St. Clair River should not be taken at this time. However, they identified major gaps in knowledge concerning natural trends and patterns of water and sediment conveyance in this important corridor. New information is needed to separate natural from anthropogenic influences and develop a long-term management plan. Here we present an ongoing strategy to extract geologically preserved clues in coastal and riverine sediments of lakes Huron and Erie and the St. Clair River, revealing natural trends and patterns of water and sediment conveyance in this important geological and historic corridor. An outlet-paleohydrograph has been reconstructed for Lake Huron from the closest strandplain of beach ridges in Lake Huron at Ipperwash, Ontario to reveal natural water-level fluctuations experienced at the outlet during the late Holocene. Three spit-fingers at this outlet (Port Huron-Sarnia outlet) are being investigated further to determine the volume and timing of sediment pulses delivered into the mouth of the St. Clair River, naturally modifying outflow from Lake Huron and river conveyance to Lake St. Clair. New research has been initiated in the St. Clair Delta to better understand natural fluctuations in water and sediment from the St. Clair River into Lake St. Clair. And future research will be focused on reconstructing paleohydrographs from strandplains of beach ridges in Lake Erie to compare with the Lake Huron outlet paleohydrograph and St. Clair spit-fingers and delta.