The Strange Woman has been very busy as of late: collecting additional data for a paper that is the second to last paper to come out of my doctoral thesis. These last two papers are the result of the data at the end of my analyses showing me something cool that I had no time to expand on for the thesis. Sometimes research does that to you: sometimes discoveries have their own schedule. I'm also doing other things that I'll hopefully be able to write about in the future. Right now I'm in finger-cross mode with those things.
This is to say that I am still not ready to post the results of our summer's work at the Six Peaks Dinosaur Track Site. What I can do is show you a video we had done on the site. Here is a teaser for you!
I will share a dinosaur track field work story with you. This one dates back to 2011, and tells the tale of how we spent the night in a pile of leaves at the end of October in northeastern British Columbia.
The best laid plans of rodents and researchers...
Fieldwork in the Peace Region of British Columbia is not simple under the best of conditions, with the best conditions being fair weather in mid-summer. There are practical reasons for this. Materials don’t set well in cold or wet conditions. The ground is either too wet (for the spring) or too frozen (for the fall and winter) to safely remove fossils. Many times the weather renders the conditions too dangerous for field crews. This is why the paleontology research field season is short in the North. The PRPRC’s typical field season runs from June-September. If the snow and sub-freezing temperatures permit it, we’ll do short excursions well into the first half of October. It’s an exceptional discovery that will bring us into the field in end October or early November.
This is the story of one such exceptional discovery.
The site was discovered by a regional guide-outfitter, Aaron Fredlund, in 2011. He had come across a small exposure of grey sandstone sticking out from under a hill of Ice Age silt, mud, and boulders. Being an experienced tracker of modern animals, it didn’t take Mr. Fredlund long to notice the large, three-toed footprint and identify it as the track of a large meat-eating dinosaur. It also didn’t take him long to reason that, if he cleared some of the debris off of the rock in front of the footprint, a second footprint could be uncovered. He was correct. The two images were immediately reported to me, Dr. Richard McCrea, and Dr. Charles Helm. A combination of the track type (large theropod) and the age of the rocks (Late Cretaceous, approximately 72 million years old) led us to identify these footprints as those of tyrannosaurs!
Tyrannosaur footprints were not unknown to science: “singleton” footprints have been reported from the Late Cretaceous (Campanian - Maastrichtian) deposits from the US, Canada, and Mongolia. However, what palaeontologists were missing was a trackway: a series of footprints made by one animal. Isolated footprints are like finding an isolated dinosaur bone, while trackways are like finding a complete skeleton. A trackway of a tyrannosaur would provide a tonne (pun completely intended) of information on how this tyrannosaur moved when it was alive. Tyrannosaurs are the best-known dinosaur predator, but their footprints were the least well-known. This site had the potential to change all that.
At the time of reporting, both Rich and I were out of town. Charles made a visit to the site with Mr. Fredlund in our absence so he could report site conditions and access. There was no GPS data taken during the visit (one of those frustrating “I can take you right to the site” situations), Charles reported from the site visit that the locality was both treacherous and tricky to access, and would require an ATV to haul in the research equipment safely. In short, we would need a guide.
Fast forward to October 23, 2011. Charles had a break in his busy schedule to visit the site with us. This was our only opportunity to get the site documented and replicated before the end of 2011. We were starting to head into winter: there was no snow yet, but the daytime temperatures were not above 10°C, and the nighttime temperatures were hovering around and just below 0°C. We could not physically remove the trackway, so we had to make a silicone mould (or peel) that would be used to make an exact replica that could be housed (and studied) inside during the winter. As difficult as fieldwork is, cold exacerbates all difficulties. Since silicone doesn’t set up in cold settings, we had to both mould the trackway and heat the silicone so that it would cure properly. This was a large trackway: the two exposed footprints covered a distance of over 2 meters long, and almost a meter wide. We would need A LOT of silicone. Silicone is an expensive molding material, but this site was worth it.
We spent that week gathering silicone, mixing buckets, brooms, brushes, documenting equipment, and all of the gear we would need to keep the silicone peel warm enough to set: tarps, propane tanks and heaters. Me, Rich, and our field technician Tammy Pigeon had all of the field gear ready to go and loaded into the ATV on Friday. We were scheduled to leave Sunday, so we thought we had a full day (Saturday, October 23) to gather our personal field gear, which had been all packed away for the winter.
We got a call early Saturday morning. Charles’ schedule had changed: could we possibly head to the site that morning? We scrambled to throw together our personal field gear. An hour later we were ready to go...or, at least, we thought we were ready.
Cue ominous music.
We followed Charles out to the “trail head”: a labyrinthine series of decommissioned logging roads long overgrown with dense brush. We scouted the best path for the gear-laden ATV among the bogs, pits, and tumbles of burnt log piles. After a long while we reached the top of the hill: at the bottom of the steep slope was the humble little rock exposure containing the tracks of one of the most famous and charismatic predators ever known.
NOTE: there will be very few pictures of the trail down to the site and of the overall site. This site is still vulnerable to vandalism and general people nastiness that all of our publicly accessible sites have experienced. The selfish actions of a few do ruin things for the many.
Once we uncovered the camouflaging coating of rubble from the track surface, Tammy and I set to readying the track surface for the silicone mould. We were expecting to have to do a bit of digging, brushing, and wiping. What we were not expecting was to have to clean a 30 cm layer of kaolinite (clay) out from the all of the nooks and crannies of the footprints. This clay was stubborn: it required several washes and (soft) scrubbings before all of the clay was removed from the footprints. Removing the clay coating from the surface revealed small skin impressions that we would have never seen (or moulded) had the footprints remained “dirty”.
As frustrating as the clay was to clean out of the skin impressions, it was very exciting to see: this type of clay forms from volcanic ash falling onto the footprints soon after they were made. This told us that the weather patterns were right for a volcanic ash layer to fall on northeastern British Columbia 72 - 74 million years ago. Perhaps our tyrannosaur actually saw the glow of the eruption? We’ll never know, but it is fun to imagine.
The track surface cleaning took a long time. In the meantime, Charles and Rich moved the research and moulding equipment to the site by easing the AVT down the hill. What goes down was not going back up: the hill was too steep for the ATV to make a return trip using that route, but we had planned for this: an alternate route was mapped out using Google Earth for our regress. Rich calculated where the third footprint in the series would be if it were preserved. If you know approximately how long of a step the trackmaker was taking, which we had from Footprint #1 and Footprint #2, you can figure out where Footprint #3 would be, even if it is still covered in rubble. Charles and Rich began excavating at the base of the hill to search for the third footprint, and successfully uncovered it!
|The first tyrannosaur trackway. a) The second footprint in the trackway. b) The exposed trackway. You can see, way at the end of the trackway, the pale clay layer that we had to clean out of the footprints. Modified from Figure 2 of McCrea et al. (2014).|
While Tammy and I began the detail cleaning of Footprint #3, Rich got to work documenting the exposed trackway. This is when he noticed something odd about this trackway. The Footprint #1 made by the left foot, was a little damaged by weathering. The inner toe (digit II) was not completely preserved: it seemed too short. Footprint #2, from the tyrannosaur’s right foot, was uncovered by Mr. Fredlund, and all of the toes were beautifully preserved. When we finished cleaning out Footprint #3, made again by the left foot of the tyrannosaur, we saw that digit II was too short on this footprint. This was not damage due to weathering: this animal was missing the end of its inner toe! This is called a pathological footprint: check out McCrea et al. (2015) for a detailed description of injuries seen in dinosaur footprints.
|Figure 7 of McCrea et al. (2014), photogrammetric rendering of the first tyrannosaur trackway. You can see the consistently missing digit II impression. I might call this specimen "Stumpy".|
Charles had to leave the site around 3pm. That was when we were finally ready to start the silicone mould. Silicone is easy to mix by hand in small quantities at room temperature. However, I had to mix large batches at around 5C. Silicone is very, very stiff when it’s cold: it’s like trying to stir molasses or all-natural peanut butter that has been sitting in the fridge. Silicone also doesn’t set properly if the catalyst and reagent aren’t thoroughly mixed: it just stays a gloopy, slimy mess.
There is another drawback to late year fieldwork: the lack of daylight. The light and temperature started to drop as I stirred, and stirred, and stirred. Each batch took about half an hour to properly mix, and then another half an hour to pour. By the time we had mixed and poured four batches of silicone, and had set up the heating tent over the silicone peel, it was 6:30pm and dark. Ice had started to form on standing pools of water. Our breath frosted in the air. It was going to be a cold, clear evening.
This is when we discovered just how rushed we were when packing our personal field gear. We had food, guide tarps, GPS, satellite phone, and warm(ish) clothing, but we had forgotten one crucial piece: The Flashlight. We weren’t initially concerned: Rich had mapped out a seismic cut line that we could use with the ATV (which has headlights) to get back to the field vehicle. It was a slow, bone-jarring trip through the dark wilderness, but we reached the opening to the cutline. We were home free...
...or not. Between Google Maps taking the images of this route and our escape (about two years), a beaver had made a dam, turning what would have been a steep but manageable slope into a large pond abutting a steep grade. There was no way to drive around the pond. After expressing a few non-printable words towards beavers and all of their kin, and finding out that similar access points were also cut off, we made our slow creeping way back to the track site.
|Bwaahaahaa! Image link.|
We returned to the site around 11:30pm. After checking that the heating system for the silicone peel was still working, we surveyed our possible lighting resources. GPS screens emit light, but not enough light to hike through the woods. Makeshift torches of burlap do not work unless you can soak the ends in pitch. We had gasoline, but that burned too quickly for a consistent light source. None of the screens on our 2011 flip phones gave enough light to safely hike by (this was before phones with flashlight apps). The Moon was not full enough to hike by, and our trail was treacherous even in full daylight. We had no choice: we were stuck for the night at the track site.
I called Charles on the satellite phone to let him know our situation. The phone made an unstable connection, and all I could get out was “Hi Charles, we’re OK, but stuck at the site for the night...” when the connection broke. Satellite phones are great for remote field work, but at that particular time our satellite coverage was poor, and we were in a canyon. What I had wanted to tell Charles was that we were stuck for the night, but could wait until dawn to make our way back to the truck.
We assessed our emergency camping options. We set up our first camp on an open patch of ground, with our backs to the ATV and facing a nice fire. We used our backpacks in place of a ground pad, and huddled under the guide tarp. We were fine here until the winds shifted direction. The ground cooled and sucked the warmth right out of us. We then moved our makeshift camp into the shelter of the woods. While Rich cleared a safe area for a fire, Tammy and I built a huge pile of dried leaves. Once the fire was going we burrowed into the leaf pile and pulled the guide tarp over us.
I actually fell asleep. I can sleep in just about any situation, and after the long day and finally being warm and comfortable, I slept like one of the rotten logs on the ground next to us. All of a sudden my lovely sleep was interrupted by loud crashing down the hill and shouting. It was an unexpected rescue party! When I had called Charles, he interpreted the call as a “please come rescue us” call. After letting people in town know we were safe, he, Thomas Clarke, and Pearl the Helm Dog hiked along that horrendous trail in the dead of night to bring us home. They reached our campsite around 3:30am.
My first emotion? I will admit that it was annoyance at having been woken up (this will be the first time Charles will hear this confession). I was prepared to sleep for another couple of hours. Part of my brain wanted me to grumble “Go away!” I was the only one thinking that: Tammy admitted to feeling quite chilled and uncomfortable. We extinguished our fire, packed up our gear, and followed the lights of our rescuers back to the truck.
There, sitting on the front seat to add insult to injury, was a flashlight that had fallen out of one of our backpacks.
|Every field bag and field jacket that I own now sports this teeny little flashlight. Lesson learned.|
This trackway was well worth the unexpected overnight camping trip. Later visits to the site in 2012 and 2013 gave us time to clear off more of the track surface, revealing two more tyrannosaur trackways. All three trackways were walking at a leisurely pace (between 6.4 and 8.5 km/h) in the same direction and were spaced evenly apart (about 3 m). We were also able to figure out approximately how old the track-makers’ were when they made their journey from present-day British Columbia to Alberta: the track-makers were between 25 and 29 years old. This may sound young to us, but this is close to the upper age range known for Albertosaurus sarcophagus (Erikson et al. 2010).
|Figure 3 of McCrea et al. (2014). I'm working on cleaning out one of three trackways, and cursing at clay.|
This site has great potential for further excavation: all three tyrannosaur trackways head into the hill. Unfortunately that hill is very high and steep, so any future work will require a lot of resources to move the mountainous amount of silt, sandstone, and mud from over the track surface. We cannot safely tunnel into the hill to expose more tracks: that seems like a plan riddled with Wile E. Coyote kinds of danger.
Hopefully this tale of working on the terror of tyrannosaurs - and a fairly epic field work fail - will amuse and entertain until I can get to the Early Cretaceous track site work we did this summer. Stay tuned!
Currie PJ, Eberth DA (2010) On gregarious behavior in Albertosaurus. Can J Earth Sci 47: 1277–1289. doi: 10.1139/e10-072
Erickson GM, Currie PJ, Inouye BD, Winn AA (2010) A revised life table and survivorship curve for Albertosaurus sarcophagus based on the Dry Island mass death assemblage. Can J Earth Sci 47: 1269–1275. doi: 10.1139/e10-051
THIS POST: McCrea RT, Buckley LG, Farlow JO, Lockley MG, Currie PJ, Matthews NA, et al. (2014) A ‘Terror of Tyrannosaurs’: The First Trackways of Tyrannosaurids and Evidence of Gregariousness and Pathology in Tyrannosauridae. PLoS ONE 9(7): e103613. doi:10.1371/journal.pone.0103613
McCrea RT, Tanke DH, Buckley LG, Lockley MG, Farlow JO, Xing L, Matthews NA, Helm CW, Pemberton SG (2015) Vertebrate ichnopathology: pathologies inferred from dinosaur tracks and trackways from the Mesozoic. Ichnos 22(3-4):235-260.
Tanke DH, Currie PH (1998) Head-biting behavior in theropod dinosaurs: paleopathological evidence. Gaia 15: 167–184.
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