In 1912, Alfred Wegener proposed the idea of continental drift. The complementary shapes of western Africa and eastern South America were one bit of evidence. The chemical similarity of minerals on those two coasts was additional evidence. But no one could explain how continents could “drift,” so the idea was not generally accepted. Then, in the 1960s, deep-diving submarines began exploring the ocean floors. One of their discoveries, ocean floor spreading, turned out to be the mechanism that caused slabs of the earth’s crust to move. Now, plate tectonics, the term that replaced continental drift, is an accepted scientific concept. Vancouver Island owes its current location to plate tectonics. Deep down, at the bedrock level, it’s made up of chunks of crust that have only recently (in the last 55 million years) joined up with North America.
Much of the geological knowledge of the Fanny Bay area is built on the work of John Gladstone Fyles. In the early 1960s, working for the Geological Survey of Canada, Fyles mapped the surficial geology (i.e., the stuff lying on top of bedrock), primarily glacial deposits, from Comox to Cameron Lake. He did this by observing “exposures.” An exposure refers to a place where a stream has, over thousands of years, cut through a chunk of the scenery and allows us to see what lies below.
In the 1990s, Corilane Gwyneth Cathyl-Bickford mapped the deeper (Cretaceous) bedrock deposits from Comox to Ships Point and beyond, walking many of our local streams from shoreline to snowfield. Like Fyles, she was searching for exposures that might reveal the underlying structure. This was an important incremental step from our perspective since bedrock can be the lower boundary of aquifers.
The last two summers, BWS has helped scientists from the University of Victoria add to the current knowledge of our aquifers. Rather than mapping geology by reading stream banks, they have been probing the depths with electricity. Using a technique called Apparent Resistivity Sounding, they have acquired nineteen new data points in the area between Royston and Bowser. These points begin to fill in the “blind spots” where there are no convenient exposures. This means we are no longer dependent on what the natural world has chosen to reveal. We can peek behind the curtain.
The results of the 2021 fieldwork will be published in the BC “Water Science Series” (3) in the Fall of 2022 and will be publicly available online. As a teaser, you can expect to see a 60-page document including maps and diagrams of our local aquifers, as well as discussion about shallow and deeper geology, faulting, mapping of saltwater incursion and plans for future work.
Science marches on!
References:
(1) Fyles, J.G. 1960. Surface Geology of Courtenay, Comox, Nelson, Nanaimo and Newcastle Districts, Vancouver Island, British Columbia, Ottawa: Geological Survey of Canada.
(2) Cathyl-Bickford, C. G. and Hoffman, G. L. 1998. Geology of the Tsable River area, Comox Coalfield, British Columbia. British Columbia Ministry of Energy and Mines, Geological Survey Branch Open File 1998-07, Sheet 6 and 7 of 8.
(3) The Water Science Series was developed by the B.C. Ministry of Environment, Water Protection and Sustainability Branch as a water focused technical publication for the Ministry of Forests, Lands, and Natural Resource Operations and the Ministry of Environment.