LATE-GLACIAL AND HOLOCENE EVOLUTION OF LAKE ONTARIO: LAKE-LEVEL, ISOSTATIC REBOUND, AND SEDIMENT DEPOSITION

Multiple techniques of geological data collection employed in the Eastern Lake Ontario (ELO) region reveal a chronology of post-Pleistocene lake level fluctuation, isostatic rebound, and resultant sediment deposition. Topographic analyses of shoreline features reveal an elevated Lake Iroquois coast approximately 134m (440 ft) above the present Lake Ontario level. Additionally, sub-bottom profiles indicate a coast 35 m (115 ft) below the present lake level, which was a result of the opening of the St Lawrence valley (10,000 BP) by deglaciation, and a subsequent arid period in the region (5,000-3,000 BP). Differing elevations and the inclines of north-south (37/1000) and east-west (1.6/1000) Lake Iroquois shore, reveal that the greatest net isostatic rebound occurred on the north and east sides of the ELO region. Sub-bottom profiles reveal a complex pattern of sediment distribution in the ELO basin caused by melt water, glacial reworking, and erosional exposure during variations in lake levels. Within the complex record of deposition a set of previously undocumented sedimentary features were identified, and interpreted to be indicators of soft sediment faults, lake floor springs, gas pockets, and turbidity flows. Each feature is a result of post glacial depositional and hydrological processes. All data generated in this project were considered in relation to previously published works on this particular region to create a more detailed geochronology of the post-glacial lacustrine environment in the ELO basin.