DIGGING UP FOSSILS

What is a dig site?

A dig site is a localized area where numerous fossil remains are found and excavated by paleontologists. For example, if a herd of dinosaurs drowned while crossing a flood-swollen river, their bodies could have been deposited in a bend of the river. From there, their bodies would have been covered with mud, and fossilization would have taken place. Millions of years later, if a fossil collector discovered a few exposed fossils and subsequent exploratory digging uncovered a large amount of fossils then the area would become an active dig site.

A site where excavation is currently ongoing (or was worked in the past) is generally referred to as a quarry; after all, you are digging into the rock similar to a rock quarry collecting rock for commercial purposes, such as limestone or marble. Many times these quarries are named after the collectors who first found the fossil remains, such as the Mygatt-Moore Dinosaur Quarry near the Colorado and Utah borders; others are named after nearby towns.

How do paleontologists dig for dinosaurs?

Once an initial bone find has been made, evaluated, and the decision made to dig further, the process of excavating the rest of the bones commences. This is, contrary to the perception given in the media, a long, hard, labor-intensive practice, especially if the dinosaur was large and a complete skeleton is present. The overlying rock must first be removed, using appropriate tools. These tools can range from dynamite, bulldozers, and jackhammers to picks and shovels. Once this overlying layer has been removed, finer tools, such as dental picks and toothbrushes, are used to expose the upper bone surfaces. To prevent these exposed bones from drying out, cracking, or oxidizing, they are stabilized by applying appropriate chemical hardeners.

The exposed bone surfaces are then completely mapped, and a plan for the excavation of the entire skeleton is made. The first step is to isolate each bone, or group of bones, by digging vertical trenches around each, leaving a substantial thickness of rock in place for protection. Any bones exposed on the sides by this trenching should be stabilized, and each bone must be numbered with permanent ink and recorded on the map records.

The exposed bones on the top and sides are covered with layers of damp newspapers, tissues, or paper towels; then, the top and sides are covered with a jacket of plaster-soaked burlap strips. When dry, this jacket locks the bones into the rock, preventing any cracking or damage. Next, the rock on the underside of this block is carefully removed, a little bit at a time. Any exposed bones are again stabilized, and the newly exposed areas are jacketed. Pieces of wood or metal prop up the jacketed block as the amount of rock on the underside is slowly reduced.

Once this rock is small enough, and all the rest of the block has been jacketed, the block can be turned over. But before that, labels are placed on the jacket with permanent ink, indicating the mapping number for each bone inside, an orientation arrow, the date, the site name and number, and any other information needed by the museum for restoration. After the block has been turned over, any remaining exposed area of rock is jacketed and the bone or group of bones is ready for transportation to the museum.

Who first developed a method to protect excavated dinosaur bones?

Not only did a plethora of dinosaur bones result from the rivalry between Edward Drinker Cope (1840-1897) and Othniel Charles Marsh (1831-1899), but new methods to protect the precious excavated dinosaur bones were also developed, as well. For example, Copes crew preserved fossils using jackets of burlap bags dipped in a paste of overcooked rice. This pasty rice mix was slathered over the burlap covering the bone; as it dried, it hardened enough to allow the bones to be safely shipped back to the eagerly awaiting scientists.

 
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