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Working our Fingers to the Bone (Layer)

May 17, 2013

On Wednesday we each returned to our holes we had dug the day before and started the bone searching right away. Unfortunately, I dug in my little unit of dirt all morning and never came across a single fossil. It can be rather disheartening to realize that you just spent the past 4 hours chiseling away at a pile of dirt only to find more dirt at the bottom and nothing else of significance. Nonetheless, this is the process; sometimes you find what you are looking for, sometimes you find nothing at all, and sometimes you even find something completely unexpected. The adventure is in the search for what might be — or might not be — hidden below!

The afternoon brought more luck as we scraped and shoveled through the layers of rock, mudstone, and clay before reaching the bone layer (where the desired fossils are most likely to be found). Two of our volunteers — Nancy and Nancy — recovered an overlapping mass of bones in between their respective work areas. The arrangement and fragility of the bones made excavating on site difficult and made jacketing the specimen necessary. Jacketing is a technique that was founded and practiced by some of the earliest American paleontologists in the 18th and 19th centuries. It is a technique that paleontologists still find useful today! In brief, jacketing a specimen can be summarized in a 5-step-process:

1) Find a fossil! Here, Nancy is pointing to the mass of bones recently discovered.

Bone mass

Bone mass

2) Create a pedestal. This means digging a trench around the specimen while slightly undercutting the dirt layer at the very bottom. This creates a mound of dirt to support the specimen in its removal from the site, travel back to the museum, and prep in the lab.

Bone mass on pedestal

Bone mass on pedestal

3) Apply the plaster! After mounting the specimen on a pedestal of dirt, you want to apply a layer of tin foil over the fossil (for protection) before applying the plaster cast. The plaster and water are combined to create a gooey and quick-drying mixture. Working quickly, burlap strips are dipped into the mixture, applied tightly and evenly across the pedestal, and left to harden and dry, thus protecting the specimen from the field to the lab. The plaster and water mixture is essentially the same material that comprises a cast one might wear to help heal a broken bone.

"Jacketing" the specimen

Jacketing the specimen

4) Map your specimen. Next, you want to ensure that you record where you found the fossils. This is important information for research purposes now and in years to come.

Mapping the specimen

Mapping the jacket

5) Let it dry! Finally, the plaster encasing the specimen will need to dry. This usually takes at least 2 hours. Once dry, you can undercut the bottom-most dirt layer and flip the jacket upside down. Then it is time to cover the base with tin foil and apply the plaster to the bottom of the pedestal, completing the jacket process.



Today we found several more fossils in need of jackets. I mixed the plaster and water and helped apply the dipped burlap onto a number of the pedestals. The below photograph is my attire in the aftermath of the jacket process. In the end, it looked like I tried to plaster up myself instead of the fossils. It is a messy job and practice makes perfect….

Me (the amateur jacketer)

The amateur jacketer

One Comment leave one →
  1. Sam Schmidt permalink
    May 17, 2013 8:30 am

    Excellent! I really like the theme and how you dumbed it down for anyone/everyone. Nice job (as always)!


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