by Tony L’Orsa*
Sheila and Lynn are celebrating having lived beside the Driftwood Canyon fossil beds for more than forty years and I have been asked to present a little of our current understanding of some of the stories that the fossils tell us. A few million years ago, the spot where they are living would have been beside or in a lake, rather than beside a creek.
The Driftwood Canyon fossil beds are a remarkable natural library. The pages of this library are thin layers of sediments that were deposited annually and upon which were imprinted the records of a few of the happenings at that place and time. That place was a freshwater lake and the time was about 51.77 million years ago, during the Eocene Epoch on the geological time scale. The age was obtained from uranium-lead dating of the mineral zircon found in a layer of volcanic ash. The exceptionally well preserved fossils here offer us a few glimpses into a little-known part of Earth’s history.
Figure 1: Pages of history in the Driftwood fossil beds. The rocks shown above represent thin layers of mud, fine-grained silt, and local bands of volcanic ash that settled on the ancient lake bottom now exposed at Driftwood Canyon.
Image by A. L’Orsa.
The formation of the ancient lake now exposed by Driftwood Canyon approximately coincided with the onset of basaltic volcanic activity in this area about 51 million years ago. In this general area, there is some evidence that basaltic flows locally blocked river valleys and formed lakes. Basaltic mountains, such as China Nose Mountain near Houston, are remnants of some of these volcanic events and have their own stories to tell. Driftwood represents the most northern of dozens of fossil-bearing lake and swamp exposures of similar age that have been discovered southeasterly from here, through the Cariboo (Horsefly), Kamloops (McAbee), Falkland, Princeton and down to Republic, Washington. This discontinuous and time-restricted accumulation of fresh-water sediments, with many fossils in common, represents fragments of a relatively warm upland ecosystem, now collectively referred to by researchers as the “Okanagan Highlands” (including Driftwood). In addition, there are extensive lake deposits of similar age in Colorado, Utah and Wyoming, which also contain many superb fossils.
The early Eocene was an interesting time in Earth’s history. Earth was experiencing one of its several “greenhouse” climatic events. The climate was much warmer and wetter, and there was probably no permanent ice at the poles. Atmospheric carbon dioxide levels are estimated to have been much higher than they are today. Average temperatures were apparently a little warmer than in southern coastal British Columbia at present. Fossils of palms and members of the walnut family indicate an even warmer climate at lower elevations. Many of the trees listed below also grew in the High Arctic at this time, where exceptionally well-preserved fossil forests have been discovered, as well as fossils of alligators, turtles and many mammals. The “greenhouse” conditions peaked about 50 million years ago and then the temperature started to decline. By the end of the Eocene Epoch, Earth was rapidly cooling down to the “icehouse” conditions that we consider “normal” today.
Plant fossils that have been reported from Driftwood Canyon include alder, birch, cypress, elm, false larch (Pseudolarix), ferns (especially the floating fern, Azolla), fir, ginkgo, hemlock, oak, pines (note Pinus driftwoodensis), redwoods (Metasequoia and Sequoia), sassafras and spruce. Some of these tree groups still grow in the area, but many others now only grow naturally in warmer and moister climates in Asia (e.g. dawn redwood, false larch and ginkgo) or farther south in North America (e.g. oaks and redwoods).
Two examples of fossil tree leaves from Driftwood Canyon are pictured below, followed by pictures of their nearest living relatives. These pictures help to remind us that these fossils, although they may now appear rather dull, were once live, green and vibrant plants living in a lush lakeside forest.
Dawn Redwood (Metasequoia sp.).
Photo by Ken Pugh.
Dawn redwoods were common in western North America in the Eocene, but gradually became extinct, or so it was thought. In the mid-1940s, a Chinese forester found a few “living fossil” dawn redwoods in a forest in southwestern China, apparently on the verge of extinction. Seeds and seedlings were collected and now these trees can be seen in gardens and parks around the world, including in southern British Columbia.
The only known surviving dawn redwood species (Metasequoia glyptostroboides).
Image: Public Domain.
Ginkgos are another easily identified, but rarely found, fossil at Driftwood Canyon. They represent a “living fossil” that can be traced back more than 200 million years. Ginkgos are locally common in the sandstones of the Skeena Group that probably directly underlie the Driftwood Canyon fossil beds and outcrop in places downstream along Driftwood Creek. Although these trees had an almost worldwide distribution some 200 million years ago, for many years they too were thought to have been extinct in the wild, but they had been preserved in temple gardens and other cultivated places in the Orient. Recently they too have been found growing wild in a few Chinese forests. Extracts from the leaves have long been used in Chinese medicine.
One half of the leaf below can be seen at the Bulkley Valley Museum in Smithers. The other part is in a private collection.
Ginkgo adiantoides. Identified by Glenn Rouse, UBC. Scale in millimetres.
Image by A. L’Orsa.
The last known surviving ginkgo species (Ginkgo biloba). This young tree is growing in Halifax.
Image by Judi L’Orsa.
The scientist who has been at the center of plant fossil research at Driftwood Canyon in recent years is David Greenwood, a specialist in plant fossils at Brandon University. He is the leader of the Okanagan Highlands Project. For more information on his work, click here for his website.
Insects reported from Driftwood Canyon include lacewings (note Pseudochrysopa harveyi, named in honour of Gordon Harvey by Bruce Archibald), March flies, crane flies, snakeflies, mosquitos, water striders, bees, wasps, gnats, earwigs, ants and termites. Some of these species are only found in warmer climates today. Bruce Archibald, Simon Fraser University, has recently been studying the insects from Driftwood Canyon and other Eocene sites. His website is here.
March fly Plecia (?) from Driftwood, private collection.
Photo by Ken Pugh.
Fish fossils found at Driftwood Canyon include the important “dawn salmon” Eosalmo driftwoodensis first described by Mark Wilson, who teaches at the University of Alberta. It is the oldest known fossil member of the salmon family. The dawn salmon has since been identified at a few other Eocene sites in British Columbia and at Republic, Washington. Other fish fossils found at Driftwood Canyon include suckers (Amyzon) and members of the bowfin, mooneye and trout-perch families.
Mark Wilson has not only worked on the fishes at Driftwood and other Eocene and older fossil localities, he has studied Eocene insects and he has studied the environments of deposition in Eocene lakes. To visit Mark Wilson’s website, click here.
Eosalmo driftwoodensis. Identified by Mark Wilson, University of Alberta.
Bulkley Valley Museum collection.
Image by A. L’Orsa.
Bird fossils are very rarely found, but an important discovery was made in 1968 by Patricia Pedley who split a piece of shale and found a fossil bird of the “rollers” family (Coraciidae; Primobucco). These birds have been found at other Eocene localities, especially in the Green River shales of Colorado, Utah and Wyoming. They are extinct in the Americas, but members of this family still exist in warmer parts of the Old World. Most of the living species are in Africa.
Fragmentary fossils of a member of the hedgehog family and a tapir have recently been described by Jaelyn Eberle and others, and represent the only mammal fossils reported from Driftwood Canyon to date. Click here for a review of the article.
Driftwood Canyon Provincial Park was established in January 1967, after pioneer Driftwood farmer, Gordon Harvey, donated 14 ha of his farm to the British Columbia Government, which added 9 ha of Crown Land, to cover the key outcrops of Eocene fossils exposed by Driftwood Creek. This is a Class A park and removing fossils from the park without a permit is contrary to the Park Act. However, it was Gordon Harvey’s wish and understanding that fossil collecting by the public would continue, and there were no serious attempts to enforce the rules until recently. We have to follow the rules, but there may be a way to permit public collecting provided that important fossils are recognized and preserved for study. A good solution to this problem has been developed in Republic, Washington, at the Stonerose Interpretive Center (http://stonerosefossil.org/fossilhunting/visitors-information/) where limited supervised collecting is allowed and school children are encouraged.
Fossil discoveries at Driftwood and other places continue to make important contributions to our understanding of the development of life on Earth. Now, with the Earth possibly on track for a change back to a greenhouse climate, fossils can help us understand probable responses of plant and animal communities to that projected change. There is more work to be done and a few rocks are eroding off the cliffs every year, providing easy access to new samples. However, with very limited budgets and other interesting fossil sites calling for their attention, institution-based scientists can only do so much here. Fossils left weathering on the ground are not contributing to science. Supervised fossil collecting by hobbyists and students might not only inspire potential new scientists, but might well bring us the next important discovery.
Books of Interest
Ludvigsen, Rolf, editor, 1996. Life in stone: a natural history of British Columbia’s fossils: UBC Press, 310 pages.
Tidwell, William D., 1998. Common fossil plants of western North America, 2nd edition: Smithsonian Institution Press, 299 pages.
*Tony is the elder son of Fortunat and Harriet L’Orsa who moved to Smithers in 1935. Both he and his younger brother, Joe, were born in Smithers. Tony is a geologist and has long had a special interest in the fossil beds found at Driftwood Canyon Provincial Park. Thanks for this wonderful article, Tony.