APPLICATION OF LEGACY GEOSCIENCE DATA TO THREE-DIMENSIONAL GEOLOGY OF THE GREAT LAKES BASIN

Great Lakes legacy geoscience data from the past 60 years, including seismic reflection profiles and interpretive maps on paper and film, have been recovered, repaired, scanned, and digitally processed for inclusion in the Expedition Database (ED) and the Seismic Data Archive (SDA) of the Geological Survey of Canada (GSC). ED contains information (metadata) and data (navigation, samples) related to marine and lacustrine field surveys conducted by the Atlantic and Pacific offices of the GSC. SDA contains digital and scanned analogue seismic reflection and sidescan sonar data.

The scientific significance and inherited financial value of the Great Lakes legacy geoscience data are considerable. In Lakes Ontario, Erie, Huron and Michigan, the seismostratigraphy revealed by these legacy high-resolution seismic reflection profiles provides insight to sediment thickness, depth to bedrock (or acoustic basement), and sediment stratigraphy. This information aids in the interpretation of the history of sediment deposition and lake level history and possible pathways for movement of groundwater or contaminants. A scientific publication based on these data is planned to elucidate the origin and significance of a subaquatic drumlin field in eastern Lake Ontario. Some legacy data from Lake Erie are being released by GSC Open Files. A planned scientific publication is anticipated to clarify the distribution of Late Wisconsinan sediments within the Erie basin. Another publication will address the processes that led to overdeepening of the eastern basin of Lake Erie.

Digital analysis of the Great Lakes legacy seismic data is a cost-effective method to generate the offshore broad scale 3D surfaces pertinent to the surficial framework geology layer required by the Canada-3D project. For example, sixteen geoscience expeditions in Lake Ontario were processed. The total line kilometres is 18,827, consisting of both boomer and KH 26B records. Boomer records are of lower frequency (and greater subbottom penetration) than those collected using the KH 26B echo sounder. The total number of ship days was approximately 160. Using a conservative cost estimate of $20,000 a day for ship time, to collect a similar quantity of data as captured from the legacy seismic data in Lake Ontario would cost $3.2 million.