The Basics of Paleontology

While a lot of people know that Paleontology has something to do with dinosaurs, many concepts that paleontologists utilize and parts of their jobs are not common knowledge. Let’s cover some of the basics with some common questions and answers!

Fossilization

Q: What is Fossilization?

A: Fossilization is a very slow process in which organic material is replaced by minerals.

Q: How does something get fossilized?

A: To be fossilized, the material must be buried before it has a chance to decay naturally. This cuts off oxygen and sort of vacuum seals the material away from natural weathering and any tiny microbes that would eat away at it. However, water can still move throughout mud and even rock, carrying with it trace amounts of minerals. Over time (like ‘millions of years’ long), minerals build up in the shape of the organic material, slowly replacing it with a much more durable material. After a very long time, the organic material is completely replaced by mineral, but retains its exact shape.

Q: What kind of things get fossilized?

A: Any organic material (or part of a once-living plant, animal, or otherwise living thing) can fossilize, but the most common parts that successfully fossilize are hard and sturdy, such as bones, teeth, claws, shells, tree trunks and branches, etc. It is possible for skin, feathers, or hair to preserve as well, but this is far less common and requires very specific circumstances to occur.

Q: How can you tell if something is fossilized?

A. Generally, fossils are both heavier and more brittle than their non-fossilized counterparts and typically are some shade of brown. Say you find two bones that are about the same size: one is white, porous, and lightweight while the other is heavy, dense, and brown. The second bone is likely fossilized and the first, modern.

Q: How do you even know if something is a fossil or just a plain old rock?

A: Sometimes, it is hard to tell! Fossil identification relies on knowledge of anatomy and of potential species in the area you’re searching in. For example, in Middle Tennessee, some of the fossils you can expect to find are small marine creatures like crinoids. If you know where to look for crinoids, you are more likely to find them.

One trick paleontologists use to confirm whether something is fossil bone or rock is the ‘lick test’: if you touch your tongue to the object and it sticks a little, it’s likely a fossilized bone. If not, its likely just a weird-shaped rock. Disclaimer: Use caution licking things you found on the ground, and don’t blame us if you get dirt in your mouth!

Q: If fossilization takes a long time, do paleontologists ever find partially fossilized remains?

A: Yes! More recent fossils (think tens of thousands of years rather than millions) sometimes are found partially fossilized, most often denoted by a hard consistency and light weight.

Q: How do we know how old a fossil is?

A: Buckle in: this is kind of a long answer. Firstly, the way we can date any rock is through a process called radiometric dating. They way this works, in a nutshell, is that geologists can measure any material that is radioactive by measuring its half-life. Radioactive materials like uranium degrades at a set rate (the most abundant form of uranium’s half-life is 4.5 billion years, meaning it would take that long for half of it to degrade into lead). If a geologist is examining a piece of uranium and it is half-degraded, then that piece is 4.5 billion years old. This is a very helpful rule, as when a volcano erupts, there are radioactive elements in the igneous rock and ash left behind (this is also how scientists can measure how long ago a certain volcano erupted). The layers of ash and igneous rock act as a sort of measuring stick for geologists, providing what are essentially timestamps in the layers of rock. Now as for fossils specifically, the estimated age of fossils is determined by where they are found in relation to those ‘timestamps’ in the rock layers.

But what if there were no volcanos near the fossil? In this case, paleontologists can reference ‘index fossils’, or fossils that are unique to a specific time period for reference. For example, if a fossil layer is nowhere near an ash layer but does contain a fossil that is only found in Jurassic-age rock, the rest of the fossils in that area are most certainly Jurassic too. Luckily, more data points for radioactive materials are always being discovered, which makes our understanding of the age of rocks and fossils more accurate all the time.

Carbon dating is a special form of radiometric dating that is used on extremely young fossils. The carbon that is used is a special isotope called carbon-14, which has a half-life of 5,700 years. This type of dating requires that the fossil still has carbon and has to be younger than 60,000 years to be dated with carbon.

Q: Why are there not more dinosaur fossil found in Tennessee?

A. Because Tennessee was largely under a shallow sea during the age of the dinosaurs. Learn more about that sea here!

Q: I think I found a fossil, but I’m not sure. What should I do?

A: Ask an expert! At Earth Experience, we perform fossil and rock identification free of charge. Send in a picture, or better yet, stop by the museum and let us take a look at your find.

Field Work and Fossil Retrieval

Q: How do Paleontologists find big fossils? How do they know where to dig?

A: Paleontologists do not simply find a promising looking spot and start digging. Instead, they scour an area that has produced fossils before (somewhere like the Hell Creek Formation). When they spot something poking out from the dirt that resembles bone, paleontologists will start digging around it to investigate. If they are lucky, they find more fossil bone under the surface.

Q: How do paleontologists get big fossils back to a museum or a lab?

A: Generally, large fossils are still partially covered by matrix (or rock) and requires careful preparing in a lab to fully reveal it. Therefore, paleontologists carefully unearth all the fossil pieces in the area and collect any small chunks (often called ‘float’ or ‘float pieces’) and dig moats around the larger, more complete fossils. They will then cover the fossil and the rock or dirt it is imbedded in with a field jacket, a plaster cast that hardens and protects everything inside of it. They will then dig the whole thing out of the ground and load it up to take back to a lab. For smaller fossils, jacketing and removal can be completed in a day, but a complete skeleton can take weeks, months, or multiple summer seasons to fully excavate.

Q: Where can I look for fossils in Tennessee?

The best place to find fossils in Tennessee are near creeks, lakes, and rivers. The erosion from the water slowly reveals old rock and fossils that you can find amongst the pebbles. The rock layer Middle Tennessee has on the surface is from the Ordovician period, making it very old. The types of animals that lived in what is now Middle Tennessee are all marine. The most common and easy to find fossils are crinoid stems, brachiopods, and sometimes even nautiloids. If you want to try your hand at fossil hunting, stay with a buddy/guardian, be extra cautious near the water, and be on guard for snakes and other wild animals.

Fossil Preparation

Q: What is fossil preparation?

A: Fossil preparation is the process of removing dirt and rock from collected fossils, and making any potential repairs once the fossil is clean. A person who prepares fossils is called a ‘fossil preparator’.

Q: How do preparators clean and repair fossils?

A: Preparators use lots of tools to carefully pick away rock and dirt, from small dental picks to air scribes (sort of like a tiny jack hammer) to sand blasting machines. Along the way they use stabilizing adhesives to keep delicate fossils from crumbling and strong glues to attach broken pieces.

Q: What does it take to be a preparator?

A: A good preparator needs patience, great fine motor skills, and a pinch of perfectionism. The fossil preparing process is slow and meticulous, but very rewarding for someone who likes to see the final product come together after a lot of careful work.

Q: What degree should I get to become a paleontologist or fossil preparator?

To become a paleontologist, most people go one of two routes: through geology or through biology. There are not many universities that offer an undergrad in “Paleontology”, but to be suited for a masters or even a doctorate in Paleontology, a thorough understanding of geology and biology is vital. Most go the geology route, as paleontology is an offshoot of geology.

To be a preparator, you don’t actually need a degree, but you do need a teacher. Oftentimes, fossil preparators start out as volunteers and are mentored by more established preparators. That being said, if you want a career in fossil preparing, getting a relevant degree would definitely be a good idea.