Crawford Lake: What is lying in the gunk?
Brock, McMaster researchers looking at sediment at the bottom of lake
It’s not the end of an era, but it just might be the dawning of a new age. And the proof may be lying in the gunk that has settled for thousands of years on the bottom of Crawford Lake, north of Burlington.
Researchers from McMaster and Brock universities hope the lake’s well-preserved sediment will be the definitive marker that can be used to show the planet has entered a new geological time period.
Since the end of the last ice age nearly 12,000 years ago, we’ve been living in what’s known as the Holocene epoch, which is part of the Cenozoic era. Now, paleontologists and geologists are proposing the start of a new epoch, which would be called the Anthropocene.
The idea is to mark the start of a new age, one where human activity has begun to have the dominant influence on the planet’s climate and environment.
The trick is to pick a starting point for this new epoch and the leading contender right now is somewhere around 1945 to 1950 — which marks the period when a number of nuclear bomb tests were being carried out, such as the major Trinity test that took place in the New Mexico desert shortly before the end of the Second World War.
It turns out these nuclear explosions shot tiny radioactive particles high into the atmosphere, where they would blow around the globe and then fall back to earth, either by themselves or in raindrops.
“The atmospheric system is pretty dynamic and it can transfer those particles pretty rapidly,” said Joe Boyce, a McMaster professor of geophysics and geoarcheology who is part of the research team. This is where Crawford Lake enters the picture. The lake is a unique ecosystem that’s ideal for studying sediment. It’s a small, deep lake with a limited amount of water coming in and water going out.
More importantly, the layer of water at the bottom is deprived of oxygen, so the normal bottomfeeding organisms aren’t there.
The result is undisturbed sediment that accumulates in welldefined layers, much like the rings of a tree build up.
“You can think of it being a timeline in sediments,” said Boyce. “We want to pick a timeline or a horizon which is globally significant or globally present.
“The beginning of bomb testing is a good one,” he added. “It seems to be a sensible place to put the beginning of the Anthropocene because it’s a global marker.”
This summer, the researchers were out on Crawford Lake to carefully take core samples one metre to two metres in length from the bottom sediment.
Each core sample will be cut in half and then a special X-ray machine at McMaster will analyze the chemical composition of each layer of the sample.
This will give them information about the micro-organisms that live in the sediment and how they’ve changed, how contaminants such as heavy metals have built up, and the impact of temperature change on the sediment.
Because the Crawford Lake sediment is so well stratified, it’s also easy for the researchers to count back 70 years or so and look for the evidence of radioactive particles from the nuclear tests.
“Hundreds of years from now, people will be able to come here to find 1950 and that’s the important thing,” Brock professor Francine McCarthy said in a statement.
Boyce said there’s a race on now by groups around the world hoping to have their research site designated as the official Anthropocene marker — sort of like a World Heritage designation for geological time period locations.
“Because of the preservation potential of the sediments there at Crawford Lake, it should be designated,” Boyce said.