The Mackenzie Mountains: where trilobites and gortex came to die

Saturday, November 24, 2001

by: Mario Coniglio


In the summer of 2000 I received an invitation from Dr. Mike Pope of Washington State University, to join him in an application to the National Geographic Society. We would be seeking funding for the first year of a project studying the Sekwi Formation in the Mackenzie Mountains of the Northwest Territories. The project sounded like an exciting launch to my half-year sabbatical, which was to start in July 2001. The project was to initially involve three scientists - Mike Pope, for his expertise in sequence stratigraphy and sedimentology, paleontologist Dr. Bruce Lieberman from University of Kansas, and myself, to study sedimentology and post-depositional alteration (diagenesis). In Spring 2001, Mike phoned me with the good news - that the National Geographic Society agreed to fund the project fully for the first year and we needed to start planning the field season! Our paleontologist would not be able to participate in this first field season, however, and we invited one of my graduate students, Rob Frizzell, to join us. Even though Rob's thesis is on Middle Silurian carbonates from the subsurface of southwestern Ontario, the opportunity proved to be too tempting to resist!

The Lower Cambrian Sekwi Formation is a thick succession (1000 m+) of carbonate and siliciclastic rocks that represent part of the passive margin that developed on North America's western edge before later plate tectonics resulted in the building of the Cordillera. As a result, the Sekwi rocks are now well exposed in the central and western Mackenzie Mountains within an area of approximately 60,000 km2. These rocks are a sedimentological Nirvana - they range from deeper water shales and limestones to tidal flat carbonates, and even include ancient karst surfaces! Sedimentary fabrics and primary structures are beautifully exposed, although in some areas, a late-stage fabric-destroying dolomitization provided additional challenges. The physical stratigraphy and biostratigraphy of Lower Cambrian strata in the Mackenzie Mountains received considerable attention from the Geological Survey of Canada and various mining companies in the 1960s and 1970s, in part the result of their potential as hosts for Mississippi Valley type lead-zinc ore.

View of the overturned Sewki Formation just north of June Lake. The section is overturned so that stratigraphic top is to the left. The recessive slope to the right is the underlying June Lake Formation. Tents can be seen at the bottom right of the photo.

The Sekwi Formation is an ideal succession for studying various aspects of the Early Cambrian (543-510 Ma) Earth. This time is particularly significant as the Cambrian explosion of life spanned the critical transition between the Late Precambrian glaciations and the Middle Cambrian greenhouse conditions. Several key groups of organisms made their debut during this time, such as trilobites and the sponge-like archaeocyathans, both of which are well-represented in the Sekwi Formation. Detailed sedimentological study of these rocks and their fauna promise to provide the basis for better understanding fluctuating global sea levels and climate changes on Earth during a critical and fascinating window of time.

The adventure begins

In the early evening of July 10, 2001, we left the madness of Pearson airport after the usual annoying delays, to fly directly to Edmonton, where Mike met us at the airport. We then proceeded to our hotel room at the Nisku Inn. The next morning's travel to Norman Wells, with a brief stop in Yellowknife, was uneventful. We were met at the airport by Liz Dale, our outfitter, who drove us to our hotel - the Mackenzie Valley Inn, which is a series of trailers fastened together to have a common hallway, and attached to another series of trailers which make up the dining areas. The hotel is a stone's throw from the Mackenzie River, which must be seen to be appreciated. The hotel's restaurant, as we later discovered, served superb pizza and Chinese dishes. We spent the rest of the day fine-tuning the excursion itinerary, acquiring a few last minute supplies (including bear spray, shotgun and satellite phone) and then enjoying the sights of Norman Wells.

The discovery of oil in Devonian carbonates in 1914 in the Normal Wells area was the event that eventually led to the birth of that town. Norman Wells has a resident population of about 600, and many are involved in some form, either directly or indirectly, with the oil industry. In recent years, Norman Wells has also served as a base for outdoor adventurers. The community is isolated by anyone's definition, being serviced by water and air in the summer, and air and winter road in the winter.

Our adventure began in earnest on July 12, when we convened with huge amounts of our field gear at the Canadian Helicopters hangar near the airport. Tim Simmons, our pilot, greeted us warmly, and after loading our gear and a brief lecture concerning safety in and around helicopters, we left the landing pad, flew over the Mackenzie River, and headed west into the mountains. Access to the Mackenzie Mountains is difficult - there are no roads, and lakes are rare, and flat landing spots even rarer, so fixed wing aircraft are not suitable for most purposes.

The field work

For reasons that should be clear, field work acutely raises ones awareness of weather, which was, for most of our excursion, wet, windy and overcast. Even though we had approximately 22 hours of daylight, with a couple of hours of dusk-like conditions in the wee hours of the morning, we routinely rose at 7 am, when temperatures generally ranged between 5ºC and 8ºC. Donning damp clothes from the day before and soaking leather hiking boots sometimes made us question our sanity! Rob and I soon learned that if we delayed getting out of the warm sleeping bags just long enough, it was certain that Mike would already have the stove going and a decent cup or two of Starbuck's Sumatra could not be too far away. The cold mornings even made instant oatmeal and "scream" of wheat palatable! Days typically warmed up to between 12ºC and 16ºC, although we had a 4-day stretch of outstanding clear and warm 25-30ºC weather. I discovered early on to my dismay that while my aging Gortex jacket kept me dry on rainy days in the city, it was not up to the persistent damp and wet conditions of the Mackenzies. Consequently, a large orange garbage bag, cut to my specifications, became my non-breathable, "low tech" but very functional rainwear.

This first season of field work focused on three areas in which the Sekwi Formation is well exposed. Our initial camp was established on the edge of a hanging valley just north of June Lake. Surrounded by snowy slopes and piles of rocks shed from the surrounding steep slopes, this site was, to put it mildly, an extreme introduction to the alpine camping. The camp was considerably above treeline and evidently also above anything resembling soil - our tents were pitched next to each other on a pavement composed of angular pieces of broken rock, which made sleeping pads an absolute necessity. In this camp, and the following two, we made sure that our open-air "kitchen" was a good distance from the tents, in case foraging bears came our way. Caribou were frequent visitors to this camp, so although water was plentifully supplied from the surrounding snow melt, it had to be treated. It was here that we learned that (a) mosquitoes can be quite happy amongst rocks and snow, and (b) if Mike's Nikon camera bounces 300 m down a mountain side, it will cease to function.

Our second camp was a short helicopter flight away, and about an hours trek to the Intga River in the valley below. Unlike our first camp, staking our tents in grass-covered soil was possible, but also unlike the first camp, our camp was pitched on a significant slope which resulted in creative solutions to stop our sleeping bags from sliding downhill. It was at this camp that we enjoyed our spell of hot weather, and our first real opportunity to dry out. The camp was near a small, ice-cold brook that splashed down the mountain side, and a small waterfall made a quick shower a cleansing, if not breathtaking, experience. Fortunately, we did not encounter any grizzly bears, but the area surrounding this camp showed several large excavations in the soil where hungry bears dug to reach the end of pika burrows, where they expected a warm but terrified meal.

Our third and last camp was in the Caribou Pass area, another short helicopter flight away. This was our lowest elevation camp. We shared our campsite with several bold pikas, who became progressively bolder with each passing day, eventually demonstrating their fondness for making holes in expensive tents and chewing on leather hiking boots. Our water supply at Caribou Pass was from a shallow, still pond we dubbed "E.coli Lake" in recognition of the abundant evidence of recent caribou visits. This camp was also a 20 minute walk from the headwaters to the Ekwi River, where armed with bear spray and insect repellant, I spent a couple of hours in each of the five evenings at Caribou Pass fly fishing for grayling and trout that undoubtedly had never seen an artificial fly. Except for several wider pools, this small stream was a couple metres across for most of its run, and remarkable for its clarity and depth.

This camp was also a few minutes walk to the Canol Road, which was built by the Americans during the Second World War to service a pipeline that provided an uninterruptible oil supply from Norman Wells westward across the Mackenzies, to Whitehorse and the Alaska Highway, ultimately to reach defense bases in Alaska. Although unmaintained, this dirt road/trail is now a Mecca for only the hardiest of backpackers willing to suffer several weeks of inclement weather, bears and insects. In addition, the trail is interrupted in several localities by fast-flowing rivers which must be crossed as the old bridges have long since washed away. Most well-prepared hikers now carry satellite phones for safety, and when backpackers have reached their limit (as many do and consequently do not complete the trail), a $1300/hour helicopter taxi back to civilization in Norman Wells is possible, weather permitting.

Our field work was challenging in every respect. Most outcrops of the Sekwi Formation involved scrambling carefully on jagged and sometimes slippery rocks, and perching on steep slopes (some 45º+) where we were constantly on the look-out for rock falls. At June Lake there was also the prospect of snow avalanches in certain areas. Rob and I could only marvel at how skillfully and swiftly "Mike - the Mountain Man" (there were other versions of this as well!) could leave us in the dust as we scurried our way up slopes. We made detailed metre-by-metre descriptions of the rocks of the Sekwi Formation, systematically taking representative samples every 2 m, and took hundreds of photographs. We shared tasks - observing, photographing, note-taking, and sampling. We took approximately 500 rock samples, including some large (and heavy) "teaching specimens" that were simply too wonderful to leave to the ravages of weathering! The Sekwi Formation with its textbook-quality examples of a wide variety of sedimentological features was an opportunity not to be missed!

Every day ended with a long, usually downhill, trek back to camp followed by the ceremonial removal of wet clothes and boots and replacing with them drier (not necessarily dry) counterparts; the quaffing of an imaginary cold beer or two; and then the preparation of the evening meal. Without refrigeration and with the replenishment of food supplies only when camp moves were scheduled, meals demanded the dual combination of creativity and tolerance. Mike showed himself to be a master of outdoor cooking - burritos and, to our surprise - an unholy union of hamburger helper with canned tuna - quickly became camp favourites. After washing the dishes, hot chocolate was the next event on the way to a welcome sleep. The first few nights at June Lake were the least restful sleeps, as we were jarred awake several times each night by the ominous sounds of rock falls on the not-so-distant slopes.

The adventure ends

On the morning of August 1, after nearly 2000 m of measured section and 300 kg of rock samples, we dismantled our tents and packed our gear in anticipation of our flight back to Norman Wells. At about 10:30 am, the distant sound of the helicopter's main rotor could be heard and soon Tim zeroed in to the landing spot. We boarded and flew the area for nearly an hour, checking potential sections for the next field season, then returned to Caribou Pass to load our gear for the one and one half hour flight back to Norman Wells, with one brief stop at a fuel cache along the Canol Road. We spent the next two days in Norman wells before boarding our flight to Edmonton, then back to Toronto for Rob and myself, and back to Washington for Mike.

The summer of 2001 was planned as the first of three summers of field work in the Mackenzie Mountains. The next two summers should also see graduate students working on a variety of topics that will help us better understand these intriguing rocks. In addition to field work, considerable laboratory work is needed, examining the diagenesis of these rocks, constructing a high resolution chemostratigraphy (carbon, oxygen, radiogenic strontium) for the Early Cambrian, statistical paleontological work and study of impressive mud and archaeocyathid mounds in the succession. Our initial examination of these rocks revealed quite clearly that they promise to provide considerable stimulation for the imagination in the years to come and the basis for some very exciting science.