Pliocene pollen grains reveal a warm, wet Klondike

The Yukon's gold fields are famous for yielding up the remains of large creatures that roamed the mammoth steppes of Beringia during the Pleistocene - the chilly epoch that lasted from about two and a half million years ago to 11,700 years ago.

The Yukon’s gold fields are famous for yielding up the remains of large creatures that roamed the mammoth steppes of Beringia during the Pleistocene – the chilly epoch that lasted from about two and a half million years ago to 11,700 years ago. But scientists are hard-pressed to describe Yukon mammals of the epoch that immediately preceded the Pleistocene.

“We know very little about the physical environment of the Pliocene” – about 5.3 to 2.6 million years ago – says Grant Zazula, Yukon paleontologist. “We have tons and tons of bones from the Pleistocene – mammoth, bison, horses and all these guys – but we know nothing about what mammal life was like during the Pliocene.”

We are, however, beginning to learn about Pliocene plants and the climatic conditions that would have supported them, according to a paper published last year in the academic journal Palynology: “Palynological evidence for a warmer boreal climate in the Late Pliocene of the Yukon Territory, Canada.”

The most intriguing surprise from the Klondike research, for the paper’s lead author, Northumbria University palynologist (pollen scientist) Matthew Pound, is how warm the boreal Yukon was during the epoch just before the Pleistocene. Trees and other plants of the time and place were those of today’s temperate regions, not of our familiar, if threatened, frigid North.

These plant species, as indicated from fossilized pollen, show that annual temperatures in the Pliocene were warmer by about six degrees than today, and that global mean temperatures were two to three degrees warmer, says Pound.

That may not sound like much, but such a rise is sufficient to alter our present world in ways we might not like, he adds.

“Pliocene climates may provide plausible comparative scenarios for interpreting the path of future climate warming during the 21st century,” Pound writes in the introduction to the paper.

The U.K. palynologist has not yet visited the Yukon, but a small but significant bit of the Yukon came to him in 2013, when his friend Robert Lowther, of the University of Leeds, returned from Canada with samples of dark fine-grain earth found in the Klondike gold fields.

Lowther had been surveying the distribution of gold and White Channel Gravel in the central Yukon. Much of what he found was coarse gravel, which doesn’t hold pollen grains well, but a dark band of earth running through that gravel stirred his curiosity. He turned to Pound for help.

Palynology is a branch of paleontology that focuses, literally, on microscopic fossils with organic walls, especially pollen and spores, says Pound. “Most plants produce them in large amounts, so they easily get into sedimentary systems, are easily fossilized and are wonderfully resistant to decay,” he says.

By taking a sample from that dark band in Klondike and dissolving the enveloping minerals and clay in hydrochloric and hydrofluoric acid, these pollens can be concentrated and viewed individually under a microscope.

Pollen grains display characteristic features, depending on the species. “For instance, birch pollen has a sort of rounded triangular shape, with three openings in the corners of these triangles, with little chambers … Whereas pine pollen has a central body that carries genetic material and has tufts, like Mickey Mouse ears, that allow it to drift in the wind quite easily.”

Beneath his microscope Pound found pollen from vegetation that lived in a much warmer Klondike than we have known since the mammoth heyday.

That warmth plays havoc with Pliocene animal research. If a mammal drops dead in a warm, damp landscape, explains Zazula, its bones are going to be more readily weathered, crushed and redistributed by water than the bones of a creature that has been encased in ice wedges and permafrost, such as those from the chilly, drier Pleistocene.

During the Pliocene, the bones of anything that died on the landscape were probably destroyed, Zazula says. “The kind of soil-formation processes that can take quartz bedrock and crumble it to bits probably did a number on the bones as well.”

“But there are a number of things we can learn from the Pliocene,” adds Pound.

From observing densities of pollen and spores in samples, looking at the climate tolerances of each plant, and then reconstructing an “envelope” in which these plants co-existed, scientists can tell if the region was predominantly forested or open tundra.

Corylus, or hazel, a temperate-region tree, has been especially significant in helping scientists date the mud and soil samples from Cheechako Hill.

Pine was predominant in the Pliocene in central Yukon but disappeared with the onset of the ice age. With the current warming trend, we will likely see pine forests moving north again, says Pound.

Spores from some plants, like Sphagnum moss, reveal the presence of bogs, lakes or rivers or an inland sea, as well as a higher and more geologically active water table.

Vegetation is what we’ve got the biggest grasp on for the Pliocene; it would be fantastic to be able to make predictions about what animals lived then, such as Pliocene equivalents of mammoth, or beaver, says Pound.

Soil samples from the Klondike (Cheechako Hill, Adams Hill and French Hill) have so far revealed no animal matter at all, to Pound’s surprise – no chitinous bits of insects, no tiny rodent teeth, just grains, spores and a few slivers of wood. But the palynologist hopes to be included in any upcoming research into animal life in the Pliocene.

The more we can learn about Yukon’s Pliocene plants, climate and ecosystems, the more we can dare to speculate about the fate of mammalian life in a warm North … and about the climate challenges we may face in a not-so-distant future, says Pound.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at www.yukoncollege.yk.ca/research/publications/your-yukon

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Yukonomist Keith Halliday
Yukonomist: Are they coming?

One of COVID-19’s big economic questions is whether it will prompt a… Continue reading

Yukon MP Larry Bagnell, along with Yukon health and education delegates, announce a new medical research initiative via a Zoom conference on Jan. 21. (Screen shot)
New medical research unit at Yukon University launched

The SPOR SUPPORT Unit will implement patient-first research practices

Yukon First Nation Education Directorate members Bill Bennett, community engagement coordinator and Mobile Therapeutic Unit team lead, left, and Katherine Alexander, director of policy and analytics, speak to the News about the Mobile Therapeutic Unit that will provide education and health support to students in the communities. (yfned.ca)
Mobile Therapeutic Unit will bring education, health support to Indigenous rural students

The mobile unit will begin travelling to communities in the coming weeks

Premier Sandy Silver, left, and Chief Medical Officer of Health Dr. Brendan Hanley, speak during a live stream in Whitehorse on January 20, about the new swish and gargle COVID-19 tests. (Crystal Schick/Yukon News)
Swish and spit COVID-19 test now available in Yukon

Vaccination efforts continue in Whitehorse and smaller communities in the territory

The Royal Canadian Mounted Police detachment in Faro photgraphed in 2016. Faro will receive a new RCMP detachment in 2022, replacing the decades-old building currently accommodating officers. (Joel Krahn/Yukon News file)
Faro RCMP tagged for new detachment

Faro will receive a new RCMP detachment in 2022, replacing the decades-old… Continue reading

In a Jan. 18 announcement, the Yukon government said the shingles vaccine is now being publicly funded for Yukoners between age 65 and 70, while the HPV vaccine program has been expanded to all Yukoners up to and including age 26. (1213rf.com)
Changes made to shingles, HPV vaccine programs

Pharmacists in the Yukon can now provide the shingles vaccine and the… Continue reading

Parking attendant Const. Ouellet puts a parking ticket on the windshield of a vehicle in downtown Whitehorse on Dec. 6, 2018. The City of Whitehorse is hoping to write of nearly $300,000 in outstanding fees, bylaw fines and court fees, $20,225 of which is attributed to parking fines issued to non-Yukon license plates. (Crystal Schick/Yukon News file)
City of Whitehorse could write off nearly $300,000

The City of Whitehorse could write off $294,345 in outstanding fees, bylaw… Continue reading

Grants available to address gender-based violence

Organizations could receive up to $200,000

In this illustration, artist-journalist Charles Fripp reveals the human side of tragedy on the Stikine trail to the Klondike in 1898. A man chases his partner around the tent with an axe, while a third man follows, attempting to intervene. (The Daily Graphic/July 27, 1898)
History Hunter: Charles Fripp — gold rush artist

The Alaskan coastal town of Wrangell was ill-equipped for the tide of… Continue reading

A man walks passed the polling place sign at city hall in Whitehorse on Oct. 18, 2018. While Whitehorse Mayor Dan Curtis is now setting his sights on the upcoming territorial election, other members of council are still pondering their election plans for the coming year. (Crystal Schick/Yukon News file)
Councillors undecided on election plans

Municipal vote set for Oct. 21

Whitehorse City Hall. (Joel Krahn/Yukon News file)
City hall, briefly

A look at decicions made by Whitehorse city council this week.

A file photo of grizzly bear along the highway outside Dawson City. Yukon conservation officers euthanized a grizzly bear Jan. 15 that was originally sighted near Braeburn. (Alistair Maitland/Yukon News file)
Male grizzly euthanized near Braeburn

Yukon conservation officers have euthanized a grizzly bear that was originally sighted… Continue reading

Most Read