Electronic Thesis and Dissertation Repository


Master of Science




Fred Longstaffe


The δ¹⁸O and δ¹³C of aragonitic mollusc shells were analyzed from nine sites in the Huron Basin, Ontario, Canada. These sites represent three lake phases spanning the Late Pleistocene to the mid-Holocene (Algonquin, Transitional, and Nipissing) and three depositional environments (fluvial, estuarine, and lacustrine). Depositional environment controls mollusc δ¹⁸O more strongly than climate. The source of carbon and climate control the δ¹³C of the shelly fauna. Shells from fluvial sites are most depleted of ¹⁸O and exhibit the greatest antipathetic δ¹³C-δ¹⁸O covariation. This reflects the dynamic nature of this system. Lacustrine sites have the highest δ¹⁸O and δ¹³C-δ¹⁸O shows a weak positive covariation with open hydrology, but a distinct δ¹³C-δ¹⁸O negative covariation when the water body was isolated. Estuarine δ¹⁸O lies between these two end members. These data demonstrate that depositional environment must be known before climatic interpretations are made using the isotopic compositions of freshwater shells from the Huron basin.

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