Dr. Will on finding fossils in Horseshoe Canyon

How did I find fossils in the Horseshoe Canyon Formation?

Some years ago, I was a graduate student who needed a project. My advisors put me in contact with curators at the Royal Tyrrell Museum, who wanted to know if the stacking of sedimentary layers in the Horseshoe Canyon Formation followed a pattern. I spent two summers measuring the thickness of rock layers, noting which types of rocks they were and whether they contained fossils, along a 45-km stretch of the Red Deer River around Drumheller. What I learned was that the rock layers do follow a pattern, but the dinosaur fossils also follow a pattern.

I had a lot of help with the work, particularly during the fossil hunts. Jon and Patty, also paleontologists, helped me find and identify bones while we were out searching. We examined the records at the museum to locate places around the badlands that had not been collected before. Then we checked to find out who owned the land; if someone owned the land, we asked permission from the landowner before starting our fossil hunt on private property. We'd get all our gear together—hat, bugspray, gloves, water and lunch, first aid kit, raincoat, notebook, camera, and rock hammer—and drive out to the spot we'd chosen. Together, we made some important new discoveries, some of which I put in Picture #3 (above).

In one spot, we found a place where a very hard layer of sandstone had made a "bench"—a wide flat spot—exposing dozens of hadrosaur bones. The Museum later conducted a major excavation at this spot. Jon was particularly good at finding tyrannosaur teeth, which we needed for the chemistry study I described last time. Patty found a section of a whole dinosaur, bones all jumbled into a pile. I found a jaw from a baby tyrannosaur. Over the eleven weeks of our fossil hunts, Jon and Patty and I found hundreds of dinosaur bones. Our most important find was not a dinosaur at all, but a cluster of fossil leaves! One of the curators at the museum told me that dinosaurs are very common out there, but plant fossils are rare—and they are still collecting plants at that site today.

Dr. Will on how to find fossils

What does a paleontologist need to know to go out and find fossils?

You probably know that dinosaurs lived during the Mesozoic, a period of time that started on the first day of the Triassic about 225 million years ago and ended with last day of the Cretaceous about 65 million years ago. If you search for fossils in rocks that are older than the Triassic—in rocks from the Permian, which might be 280 million years old—you might find fossil fish or bones from the pelycosaurs we discussed last time, but you won't find dinosaurs because the rocks aren't the right age. Rocks younger than 65 million years old might contain fossil horses, but again no dinosaurs. In order to find dinosaur fossils, you need to know the age of the rocks you're hunting in.

Paleontologists use a special type of map called a Geologic Map that shows roads and cities (like other maps) but also the age of surface rock. Picture #1 (above) includes a section of a geologic map of Alberta, made by the Alberta Geologic Survey; on this map, you can see several swirls of color, each with bold labels: "Khc", "Kbp", and "Ks" are examples. In each case, the "K" means Cretaceous—so the rocks around Drumheller, the city closest to the Tyrrell Museum, are the right age to contain dinosaurs. However, even though a rock is the right age, it may still not be the right kind of rock to contain dinosaurs.

Rocks come in three general types, and only one type preserves fossils. Igneous rocks are melted deep inside the earth and sometimes erupt through volcanoes but are too hot to preserve fossils. Metamorphic rocks are very old rocks that have been deeply buried; they get squeezed and cooked and changed, but they're too far down to collect bones. Sedimentary rocks, which are made from sand and mud stirred at the surface by wind and water, can capture and keep old bones. These rocks come in layers, almost like a stack of pancakes. When sliced open by a river, the stack of layers is exposed, as shown in the photos in Picture #1 (above). The geologic map will show you where you can find sedimentary rocks.

Each layer of sedimentary rocks, usually called a formation, has a special name, also shown by the geologic map. You might have already guessed that the "hc" part of "Khc" stands for the "Horseshoe Canyon" Formation. "Kbp" represents the Bearpaw Formation, and "Ks" represents the Scollard Formation. Each layer is a bit different—there are lots of different kinds of sedimentary rocks too! On the map, the colors don't seem to make a stack, but that's because the hills and valleys are eroded and lumpy, as shown by Picture #2 below.

We're back!

Hi everybody!
Our Mom got a bit overwhelmed and we were really busy with having fun outside and then with back to school time, but now we are back with new adventures.

We are excited about starting to plan our trip to the Royal Tyrrell Museum next summer. We are starting to learn about all of the things that we will see on our way there. We are also starting to learn about the geology and stratigraphy (the layers of rock and earth that are formed at different times in the planet's history) of that area so we will know where to look for fossils when we get there.

Dr. Will has sent us more great information and pictures. We will work on that post now.

Thanks to all of you who have sent us messages. We really appreciate you visiting us! And we enjoyed our visit to Adventure Boy's site too! We really liked the picture of the Hadrosaur. We thought it was a Muttabarrasaurus because of the crest on its snout. And we also liked the lions by the cave.