Just another piece of wood
by Berry Wijdeven
by Berry Wijdeven
![Haida Gwaii - Cape Ball](/uploads/1/2/6/9/126967338/wood2_orig.jpg)
On the East Coast of Graham Island lies the longest dune ecosystem in British Columbia, stretching 70 kilometres from Tlell to Rose Spit. Along that stretch, north of the Cape Ball River, those dunes turn into magnificent sea cliffs. Standing below those cliffs, looking up, one is dwarfed by the sheer walls, made up of layers of sand and clay. For most of us, those layers don’t mean much, but to Rolf Mathewes these layers are chapters in a book, each telling the unique story of their geological era. Rolf is a paleoecologist. Okay, I didn’t know what that was either but basically Rolf examines geological and biological evidence from fossil deposits to find out what past ecosystems looked like.
Rolf has been coming to these cliffs since 1980 when he was asked to analyze a peat sample from the area and discovered the plant pollen in the sample was 16,000 years old. 16,000 years ago the rest of British Columbia was still covered in a thick layer of ice and would be for thousands more years. The fact that plants existed at Cape Ball at that time opened up all kinds of intriguing possibilities ranging from a unique history of glaciation of the islands to the presence of refugia where plants and animals could survive during glaciation events.
Rolf has been coming to these cliffs since 1980 when he was asked to analyze a peat sample from the area and discovered the plant pollen in the sample was 16,000 years old. 16,000 years ago the rest of British Columbia was still covered in a thick layer of ice and would be for thousands more years. The fact that plants existed at Cape Ball at that time opened up all kinds of intriguing possibilities ranging from a unique history of glaciation of the islands to the presence of refugia where plants and animals could survive during glaciation events.
![Rolf Mathewes searches the Cape Ball cliffs](/uploads/1/2/6/9/126967338/editor/wood3.jpg?1566602900)
Ever since, Rolf has been coming to the islands, locating areas of interest, taking core samples, examining old plant remains. Cape Ball has remained his favourite site to explore as it
clearly delineates various geological events. See that layer of sand with the embedded gneiss (a rock type)? Haida Gwaii has no gneiss, so that layer came from the mainland mountains, pushed here by glaciers. That band with seashells sticking out? That came from the floor of Hecate Straight, deposited when the ocean levels were much higher. And so, layer by layer, chapter by chapter, the various geological eras are stacked on display.
Using areas such as Cape Ball, Rolf has extensively studied the period prior to the last island glacation but has always been curious what other glacial periods were represented lower down the cliffs. After all, there have been at least twenty glacial advances and retreats in the last two million years. Sites like Cape Ball or bound to show at least a few of them.
clearly delineates various geological events. See that layer of sand with the embedded gneiss (a rock type)? Haida Gwaii has no gneiss, so that layer came from the mainland mountains, pushed here by glaciers. That band with seashells sticking out? That came from the floor of Hecate Straight, deposited when the ocean levels were much higher. And so, layer by layer, chapter by chapter, the various geological eras are stacked on display.
Using areas such as Cape Ball, Rolf has extensively studied the period prior to the last island glacation but has always been curious what other glacial periods were represented lower down the cliffs. After all, there have been at least twenty glacial advances and retreats in the last two million years. Sites like Cape Ball or bound to show at least a few of them.
![Haida Gwaii - Rolf Mathewes assesses piece of wood](/uploads/1/2/6/9/126967338/wood4_orig.jpg)
One day, a few years back, Rolf was walking along the cliffs, looking for anything out of the ordinary, when he noticed a piece of wood. Of course there are lots of pieces of wood on the beach, washed up by the surf or fallen down from the cliff face above, but this piece of wood was embedded in the cliffs, partially poking out. Since it was embedded in a thick layer of glacial till near the bottom of the slope, it could be part of an older glaciation event. If Rolf could age the piece of wood, he could tell when the layer was deposited.
Rolf had seen ancient pieces of wood before, sometimes millions of years old. Most often the wood was black, rotten and crumbly. But this piece looks fresh, solid and even had a wood odour. With some trepidation Rolf sent some wood fragments to the lab to be carbon dated, but the news was good. The wood was definitely old, more than 43,500 years in fact. The exact age remained unknown, however, since radiocarbon technology can’t date artifacts older than 43,500 years. Now what?
Rolf had seen ancient pieces of wood before, sometimes millions of years old. Most often the wood was black, rotten and crumbly. But this piece looks fresh, solid and even had a wood odour. With some trepidation Rolf sent some wood fragments to the lab to be carbon dated, but the news was good. The wood was definitely old, more than 43,500 years in fact. The exact age remained unknown, however, since radiocarbon technology can’t date artifacts older than 43,500 years. Now what?
![Haida Gwaii - Aging of deposit using optical dating](/uploads/1/2/6/9/126967338/editor/wood5.jpg?1566603048)
Fortunately there was a relatively new aging technique called optically stimulated luminescence, or optical dating. Using the decay of trace amounts of radio activity present in all soils it measures how long ago that soil was exposed to sunlight and translates that into a date. And that date came back as 57,000 years. Bingo!
Not only was this the first time this Haida Gwaii glaciation had been aged, it now gave Rolf an age for the ancient plant pollen he had collected just below the glaciation deposits. Using that pollen, he could now determine what plants existed and describe what the island environment looked like 57,000 years ago.
Not only was this the first time this Haida Gwaii glaciation had been aged, it now gave Rolf an age for the ancient plant pollen he had collected just below the glaciation deposits. Using that pollen, he could now determine what plants existed and describe what the island environment looked like 57,000 years ago.
![Picture](/uploads/1/2/6/9/126967338/editor/wood6.jpg?1566603100)
Turns out it was colder on Haida Gwaii. Cape Ball, in those days, was located on a coastal tundra, dominated by grasses, sedges and heath plants. There were few if any trees and the growing season was short and cold. While those finds may not sound all that exciting or inviting, there were some intriguing finds as well. Rolf identified some fungal spores in the samples he collected, spores which only grow in dung. And not any dung, but dung from larger herbivores such as mammoth, bison and cows. He didn’t find a few spores, he found lots of them, leading him to conclude that mammals were not just grazing at Cape Ball, they were congregating there. At a watering hole perhaps, or maybe to admire the view. Herds of bison at Cape Ball, where is that time machine when you need one.
![Picture](/uploads/1/2/6/9/126967338/wood7_orig.jpg)
Amongst all the sedges, grasses and heath, Rolf also identified pollen from some pretty distinctive plants. Plants which, 57,000 years and two glaciations later, still occur on Haida Gwaii. Jacob’s ladder is currently found locally in two locations, in the alpine and on an island in Laskeek Bay. The most striking find, however, was pollen from the Yellow Sand Verbena (A. latifolia). There is currently only one known location of Yellow Sand Verbena on Haida Gwaii, and it is located in an East Beach sand dune ecosystem just a few kilometres south of Cape Ball. How cool is that?