Scientists search for buried ancient river in South Simcoe

News release from the Ontario Geological Survey March 17 2011

UTOPIA — Scientists from the Ontario Geological Survey are using gravity detection devices to hunt for a buried ancient river system in southern Simcoe County.

Using extremely sensitive equipment, OGS crews are working along the sideroads of South Simcoe to measure tiny fluctuations in gravity, which can be used to determine the relative depth to bedrock from the ground surface.

 The goal of the study is to discover the dimensions of a deeply buried ancient valley and what kind of material has filled it in.

“Mapping minute variations in the Earth’s gravitational field helps us to locate buried valleys that were once occupied by the ancient river systems,” said Desmond Rainsford, a geophysicist with the Ontario Geological Survey. “Knowing where these ancient river valleys are situated will improve our understanding of the regional geology, where various groundwater aquifers are located and how extensive they might be. “

The information collected will be used to reconstruct a picture of the ancient bedrock surface that lies below the county. A drilling program planned for the summers of 2011 and 2012 will target the valley, and provide information on the sediments that overlie the bedrock surface and that may host potential groundwater resources.

This work will assist in understanding the region’s geology. The results will be used to promote informed land-use planning decisions that can help protect drinking water, and prevent overuse of stressed groundwater resources in the City of Barrie, the towns of Innisfil, Bradford West Gwillimbury and New Tecumseth, and the townships of Essa and Adjala Tosorontio.

This area is believed to overlie an ancient river system which was carved into the bedrock surface between Georgian Bay and Lake Ontario. This ancient river system, known as the Laurentian Channel, is possibly millions of years old. It was, over time, filled with layers of sediment and then subsequently, over thousands of years, covered by additional sediments deposited during various glacial events. The Nottawasaga River valley, between Wasaga Beach and Alliston, is believed to broadly overlie this ancient channel.

The sand and gravel-rich layers that were deposited in the Laurentian Valley, as well as within the overlying glacial deposits, may be host to important sources of groundwater and could provide water to ecologically sensitive streams and rivers. The finer-grained silt and clay-rich layers within the sequence protect these groundwater supplies from potential contaminants.

“Collectively, the results of this project will greatly benefit the municipalities and the conservation authorities in their on-going management of the groundwater resources,” said Nottawasaga Valley Conservation Authority representative Ryan Post.

The geoscience data and products produced by the OGS are used for a wide range of applications including environmental, land-use planning and resource assessments.