Mackenzie River

The main thrust of my current research is examining the end-Cretaceous mass extinction, and the latest plan is to search for evidence of that extinction in the Canadian Arctic.

65 million years ago, a massive asteroid crashed into the Yucatan Peninsula, leaving a crater more than 100 miles wide. Vast quantities of molten and vaporized rock were blasted into the high atmosphere, resulting in a period of cold and darkness. A host of other apocalyptic events probably coincided- the shockwave from the blast and giant tsunamis would have caused devastation even hundreds of miles away; sulfate droplets may have continued to block out sunlight even after the dust had settled; debris heated by re-entering the atmosphere could have cooked much of the life on land. It was as close to the end of the world as we've ever come in the past 250 million years. The bulk of the evidence suggests that photosynthesis was drastically reduced or shut down entirely, causing a rapid, worldwide collapse of the food chain. The result was the most severe extinction in the past quarter-billion years, one which wiped out upwards of 70% of all species on earth. At this point, it's clear that the impact was the primary, and probably exclusive, cause of the mass extinction. Dinosaurs thrived up to the moment of extinction before vanishing in a geologic instant, worldwide; that instant coincides with the impact of the asteroid. The odds of this being a coincidence are astronomical. An extinction of this magnitude is a once in 100 million year event, and an asteroid impact of this magnitude is also a once in a 100 million year event. The odds of these events occurring at the same time? Pretty long.

What remains unclear, however, is precisely how the asteroid caused the extinction. Darkness? Cooling? A thermal pulse? Acid rain? Pretty much the only way to test these ideas is to look at the fossil record to understand patterns in survival and extinction, and to then see which processes would produce those patterns. Unfortunately, the fossil record from this time period has a lot of gaps. The idea behind this project is to try to fill in some of those gaps.

One of the few good terrestrial fossil records of this time period is in the Great Plains of western North America. However little is known about how it happened in other parts of the world. With that in mind, I started scouring the literature for sites that preserved this critical interval. One of the few unexplored areas I found was located in the Arctic of Canada, just under the Arctic Circle. This site, in the Northwest Territories, along the Mackenzie River, has rocks deposited just before, and just after, the extinction.

The idea is to head up there and search for fossils to what kinds of dinosaurs lived just before the extinction, and what kind of mammals and other animals moved in, in the aftermath. The Mackenzie River, however, isn't terribly accessible. There are no roads- no permanent roads, at any rate; the river itself freezes over in the winter and you can drive on it then... not that this would help much, obviously. It's dark, it's 40 below, and the fossils are under a lot of snow. After the river breaks up in spring, you can travel along it by boat. We're working about 50 miles from the nearest town, meaning that canoes aren't terribly practical. So for part of our trip, we have to hire jetboats to ferry us up and down the river. Other places are even less accessible. The badlands of the Tertiary Hills, for instance, have only small rivers and no lakes where you could land a floatplane. The only way in and out is by helicopter.

So in late July, we're heading up to the Mackenzie River for three weeks, hitting three different sites along the way, bombing from valley to valley, hopefully not getting eaten by any bears. A local outfitter said that there aren't that many grizzlies in the area. But if he's wrong, and I'm eaten by a grizzly, I'm going to have some stern words for him.

At any rate, it's an adventure; a bit of a fishing trip. But bone has been reported from the area, which is a really good sign. The fact that nobody's looked intensively but it's still been spotted (bone is very easy to overlook if you don't know what you're looking for, and you're not actively looking) is a really promising sign... hopefully one I'm not reading too much into.