Since the summer is the field season for many of us, I thought I would write a little bit about the first step in paleontological discovery: actually going out and looking for fossils. I will admit, when I first started graduate school and had never gone on any sort of expedition, I had no idea how anyone ever found a fossil. When you ask a non-paleo person, many times, they think you just show up somewhere and indiscriminately start digging a hole hoping to find bones. I’m happy to say sometimes we are a little more efficient than that…but sometimes not by much.
Humans have been discovering fossils for thousands of years, and ancient societies have in fact recorded finding bones in the ground accidentally (a topic I am interested in writing more about for a future post!) Similarly, in the modern era, serendipity is often needed to find great fossils. Sometimes it is a farmer tilling a field, workers digging coal mines, or children out exploring; some lucky catalyzing event usually clues us in to an area’s fossil bearing possibilities.
I started my field work in the Gobi Desert of Monoglia. The tradition of finding great fossils in Mongolia is a long one, dating back to the 1920s and the expeditions of Roy Chapman Andrews. He went to Mongolia hoping to find human fossils, but actually stumbled upon a vast trove of fossils, including the first specimens of animals such as Velociraptor and Indricotherium. Because of this detailed history, we have a good idea of what specific rock formations contained fossils.
When I first went out into the field in Mongolia, I heard the story of how Ukhaa Tolgod, one of the greatest Cretaceous Mongolian fossil localities, was discovered. Basically, one of the many vehicles had gotten stuck in the sand, and so it was going to take a while to tow. The leaders of the expedition decided to go check out a red hill in the distance that looked like the same sort of rock as the famous Flaming Cliffs. When they pulled up and saw skulls and skeletons dotting the ground, they knew they had hit the jackpot. The crew has since visited hundreds of similar looking sites that appear to be the same formation, but found no fossils, so it goes to show you that if you keep your boots on the ground long enough you might only be lucky enough to find a handful of great sites!
Fossil localities are often discovered as the by-products of construction. Some famously important fossils have been found in tailing piles of coal mines, opal mines, and road cuts. But once you have found the locality, and know there are fossils there, how do you find more of them? Sometimes people get an image in their heads of paleontologists using sophisticated tools like Ground Penetrating Radar in order to find fossils. While this method does work (check here for a paper on this topic by the late great Derek Main) many scientists don’t have the resources to use these machines. They also don’t work in certain rock formations as well. Most of the time, we just put our boots (and eyes) to the ground and walk around for hours in the hot sun, rain, or cold until we see a little scrap of bone on the surface that can look like a boring rock. You need to learn what bone looks like at your locality, which can take a while. Sometimes it is white, sometimes brown, or even black. If you see a scrap of bone, it is useful to explore if it is just a small part of something big by digging around it carefully. If you see bone rolling down a small slope, you walk to the top to see if there is a fully exposed skull waiting for you to collect it (doesn’t often happen, but I wish it did).
This is what it is like in Mongolia. We don’t get out the big digging equipment unless we are fairly certain we are digging into something nice. In some places I have worked, like an Eocene locality in Australia, the heavy machinery was brought out immediately because the fossils were contained in a silty layer that was exposed meters below the topsoil. This is also a locality where you really never see the fossils you are collecting, you merely take loose piles of poorly consolidated sediments, throw them in bags, and then sieve them in the lab later to find very precious small teeth and bones. While you don’t find whole, articulated skeletons this way, sieving is a valuable methods for understanding smaller fauna at a locality.
If you are on top of a rich bonebed, you can set up a quarry, where basically everyone huddles in a glorified hole, very carefully exposing piles of bones. The way bones are found in a bonebed can be important to interpreting behavior later, so it is important to be careful. It can take weeks, months, or even years (decades!) for a fossil to make it from the field into the preparation lab, so sometimes the fossils you read about in recent literature were discovered by previous generations of scientists. For my next post, I will talk more about preparation, or everything that happens after we find an exciting fossil in the field!
Does anyone collect fossils in an interesting locality? Underwater for example? Anyone use blasting at their site to move rocks? I know some people who collect in extreme environments like Antarctica have interesting stories. Post a comment if you would like!