Summer is here in force in central Indiana; from torrential rains to very hot & humid days – it’s summer. Getting geared up and finalizing plans for our field work for this season. Feels good to be working on this after missing out and not traveling to explore last year. We’ll be going west to Montana & S. Dakota this season looking for “buried treasures.” I have four people now scheduled to join me this trip so looking forward to having the help and camaraderie.
I did a time lapse video last night in the shop showing the initial removal of surrounding matrix from a set of three vertebrae in one plaster field jacket. You’ll see my hands working feverishly removing the sandy matrix that’s mixed with hard stone pellets (concretions) that formed near the fossilising bones. It’s sandy, but still compacted hard. As usual when we first open a jacketed specimen we work from the “bottom” side first.
When the fossil is being excavated we gently expose the surface to find the outline of the bone(s). We install the plaster soaked burlap strips over this exposed “top” side of the piece then once dry and hardened we “flip” the jacket over and encase the “bottom” of the fossil along with the matrix (soil and rock) that’s encasing the bones. So we take along a good bit of the surrounding rock with the fossil to protect it. That’s what we see in this video; the thick mass of matrix we purposely encased in the plaster field jacket. This is done to best preserve the specimen so loose parts & pieces that may be present stay in place.
The fossilized bone you see appear in this video has never before been seen by anyone – not even the person who found the specimen and plaster jacketed it. So as much as you want to really uncover and examine pieces found in the field, we frequently remind each other – “don’t prep in the field.”
There’s a second discovery that happens in the prep lab as we expose the fossilized remains that have never before been seen. Discovery in the field is really cool and exhilarating and so is the 2nd discovery we do here in the lab.
I’ll post updates as this set of vertebrae gets more exposed. You can see around the centrum (center, round base) of this first vertebra how mineral has adhered to the bone surface. This mineral deposit is a different color (orangish) than surrounding sandy matrix, is really hard and is kind of locked on tight to the bone surface. Much careful, close up work awaits once the 3 vertebrae in this jacket are stabilized and removed so this mineralization can be worked off/away from the bone surface.
Here’s a 30 second time lapse video from last night. Two hours of work rush by in 30 seconds!
Here’s what the jacket looked like before we started:
And here it is with some of the hard plaster cast carefully cut back to expose the surface:
Here’s what this set of fossils looked like sitting in situ (in place before any movement) before we jacketed them:
The set of 3 vertebrae are at the top of this photo just above the hip bone that’s been freshly covered in a plaster jacket: