A driller was boring down into hard rock in December when he suddenly penetrated soft sediment.
His construction crew was blasting in preparation for a new interchange at Highway 97 and Westside Road, near the William R. Bennett Bridge, which requires scraping away tons of earth.
The unexpected discovery of soft material revealed evidence of an ancient glacier that covered the Okanagan Valley, and it changed the way scientists view the early history of the Southern Interior.
“It completely opens up an interval in history that we knew nothing about. It‘s the oldest glaciation ever discovered in Southern B.C.,” said Murray Roed, a Kelowna geologist.
Workers uncovered a three-metre layer of glacial till – the rocks and soils absorbed by a glacier and then deposited when the ice melts. The landmark discovery sets back the clock more than 1.5 million years before the earliest glaciation that scientists had previously identified in the Valley.
More importantly, it exposed a thin layer of ancient soil on top of the glacial till that contains remnants of trees, plants and other surface materials that flourished before volcanic lava erupted and encrusted much of the Westside.
The discovery has allowed soil experts and paleo-botanists to remove samples, giving them a closeup view of plant life in this area more than 1.6 million years ago. Scientists and students will be visiting the site for the next few weeks before the slope is covered with crushed rock, Roed said.
“I‘m trying to get part of the site preserved, but it‘s a slow process,” he said. “This will be a classic locality, geologically.”
Scientists have also found a partial layer of till at the same level as the ancient soil. The brick-red rock structure suggests the hot lava baked the topsoil when the Lambly Lake volcano first erupted 25 kilometres away. The lowest lava contains pebbles and other material from the till.
The glacial deposits lie beneath a series of lava flows located under Lakeview Heights. Scientists have used argon dating to age the volcanic rock at 1.6 million years old.
The lava poured out of magma chambers likely through a crack in the Bear Creek Valley, flowed south to the base of Mount Boucherie and hardened as basalt.
Because the till was found beneath the basalt, it‘s hard to specify how long ago the glacier filled the Valley. Roed speculates it could be up to two million years old, when the earliest ice age of the Pleistocene period began, and as much as two kilometres thick.
“I‘m calling it the West Kelowna advance in a paper I‘m writing,” he said.
The cross-section of material on the hillside at Westside and Sneena roads also reveals a thick layer of sand located mainly below the till. Scientists believe a shallow, fast-flowing stream carried the sand to this area before the ice age began.
The ripples and faults in the sand indicate the current at that time and the direction of flow. A series of clay dikes and strange structures found in the sand suggests that when lava thundered over the site, it stirred up the sand below and forced the clay to squirt upward.
The Westbank First Nation, which owns the land, is co-operating with scientists. Chief Robert Louie is said to be excited by the discovery.
The band has an agreement with the province to build the $41-million interchange. The three-year project will feature an overpass that will eliminate the traffic lights on Highway 97 at Westside Road.
