Evidence of Neotectonic Activity in the Lakebeds of the Lower Great Lakes and Possible Relation to Postglacial Isostatic Rebound
Abstract
Over the past 25 years the Geological Survey of Canada has conducted regional investigations of lakebed surficial geology and geomorphic features using high-resolution acoustic sources including sidescan sonar and subbottom profilers and bottom sediment corers. More recently new multibeam mapping techniques have been employed to generate high-resolution detailed 3D imagery of the lakebed. Key features regarded by most investigators to indicate neotectonic activity in the lake basins include bedrock pop-ups and sediment pockmarks. Pop-ups occur in areas of exposed bedrock in western Georgian Bay, eastern Lake Ontario and eastern Lake Erie. These linear bedrock ridges predominantly strike NW with conjugate sets occurring to the NE. Both fresh and oxidized surfaces along ridge crest fractures with non-existent to discontinuous sediment infill, and undisturbed sediments overlying buried pop-ups indicate these features have occurred over geologic time. Greater numbers appear to be older. Pockmarks or fluid vent features occur in areas of postglacial sediment cover in central Georgian Bay, eastern Lake Ontario and eastern Lake Erie as single features or as linear arrays of vents. Some pockmarks are still active although a greater number have mid to late Holocene sediment infill suggesting an older age of formation. A recently updated model of postglacial rebound indicates a negative exponential uplift curve with associated rapid initial crustal rebound in the early Holocene followed by declining rates that continue today. The more frequent occurrence of older pop-ups and pockmark features and the more rapid early Holocene glacial rebound would suggest these neotectonic features may be linked to glacial unloading when the crust experienced the highest rate of deformation.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.S13A..04B
- Keywords:
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- 7230 Seismicity and seismotectonics