Drill cores reveal wealth of geological history: SFU study

Burnaby Mountain was once an island surrounded by water and a massive volcanic eruption nearly 30,000 years ago blanketed the Lower Mainland in ash.

Those are the preliminary conclusions of two Simon Fraser University earth scientists who were given the drill cores associated with the Evergreen SkyTrain extension’s tunnel excavation. Those cores revealed a wealth of geological history dating back thousands of years.

“We discovered there was at least one volcanic eruption in the region that would have covered the Lower Mainland in volcanic ash,” Lionel Jackson, an adjunct professor at SFU and an emeritus at the Geological Survey of Canada, said on Thursday. “That was about 26,000 years ago.

“(The ash) definitely came from somewhere in the Cascades, but we don’t know exactly where. It could have been Mount Garibaldi. We know from the chemistry of the ash that it wouldn’t have been Mount Baker. One of the (drill) cores contains about a foot of volcanic ash.”

Jackson and Brent Ward have been studying the drill cores since a geologist involved in the Evergreen Line tunnelling — a graduate of SFU’s earth sciences department — told Ward that SkyTrain had no use for them, so would he like them?

“We said yes,” said Jackson of the drill cores the two have been studying since September. Four of several dozen cores are now stored in Jackson’s garage in Coquitlam.

“What really surprised me is that the drills did not encounter any bedrock at all,” said Jackson. “The tunnel cuts through a buried valley (that) was filled up with sediment” deposited during several ice ages.

“These cores represent an amazing geological archive of the glacial history of the Lower Mainland,” added Ward, noting that some cores yet to be studied extend below sea level — an earth scientist’s dream, given such material is typically unattainable in an urban area.

Jackson has determined that in the recent geological past, the passage of glacial ice produced a deep valley between Burnaby Mountain and central Coquitlam that made them islands.

Jackson is awaiting radiocarbon analysis to determine the timing of the glacial advances, and the researchers hope to access the remaining cores to complete their research.