Hairy Museum of Natural History

Part Two: Bring ‘em Back Intact

As mentioned previously, the main goal of this trip to the Snyder Quarry was to bring back a large block containing an assortment of Triassic fossils: bits and pieces from crocodile-like phytosaurs, heavily armored aetosaurs, and (most tantalizing of all) bones from an early dinosaur. The block had been defined and encased in plaster earlier this spring, when NMMNHS alum Dr. Andy Heckert (now teaching geology at Appalachian State University) brought a group of students to New Mexico for some fieldwork. By all accounts, they did an incredible job expanding the quarry and locating fossils, and the sizeable block they left behind was a fitting testament to their enthusiasm and productivity at the site.

The method of quarrying a big block of fossils like this hasn’t changed much in more than 100 years. Paleontologists define the area containing the fossils by digging a trench around the perimeter. The trench is then dug wider and deeper until the fossils are isolated within a pedestal of rock, which in large blocks can be undercut to form a sort of giant rock mushroom. The fossils atop the pedestal are covered with a layer of wet paper, and the whole pedestal is capped with sheets of burlap soaked in plaster. After the plaster has hardened into a protective jacket, chisels or other wedges are driven underneath to separate the block from the underlying rock, and the whole block can be flipped over onto its face.

Larry Rinehart and Justin Spielmann begin to jacket a smallish pedestal of rock and fossils,
while Volunteer Preparator Jim Moore heads for the burlap.

Flipping a jacket is the diciest part of the whole procedure. If all goes well, the whole block tumbles over neatly, with all its contents intact and snugly nestled within its protective plaster shell. If the flip is not done smoothly, or the plaster is weak or thin, or the rock inside is loose, or the bottom of the pedestal isn’t completely separated from the surrounding rock, then flipping the jacket can cause part or all of its contents to dump, which is never a good thing.

The larger a jacket is, the more difficult it is to flip. A ton of rock isn’t going to turn over quickly or smoothly, and something that heavy is much more likely to tear apart or break away from the thin plaster shell holding it all together. When Andy and his group first attempted to flip the jacket, the plaster started cracking in one corner and the some of the sediment began to shift inside. They set the jacket back down, and made the decision to leave it until a crew could come back, spend some time reinforcing the jacket and hopefully bring it back the the NMMNHS intact.

Which is what we set to work doing after we cleared out the quarry.

We added several more layers of burlap and plaster, paying close attention to the areas where cracking had started. We incorporated two-by-fours into the top of the jacket, that would both reinforce the jacket and act as skids once we turned it over. We drove lengths of tube steel under the block, and tied it all together with chain and ratchet straps, and by Wednesday afternoon we were ready to flip it over.

Luckily for us, Rich Wilke had brought a winch up to the site, which made the flip go much easier. Within a few minutes, Rich, Larry, and Justin had flipped the jacket neatly, and had pulled it up out of the quarry. A nine-image sequence of the flip is shown below the fold:

(more…)

—Matt Celeskey.

File under: Dinosaurs, Reptiles, The Day Job, Triassic.

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Part One: An Introduction and Overview

Composite photo of Fieldwork at the Snyder Quarry, 8/1/2007
From left to right: Justin Spielmann, the big block, Larry Rinehart, Curt Haakenson, Robert Hubbard.

Last week I was lucky enough to spend five days out in the field, as part of a team from the New Mexico Museum of Natural History and Science collecting fossils from the stunningly prolific Snyder Quarry near Ghost Ranch in northern New Mexico. The Snyder Quarry is an amazing site that preserves the remains of phytosaurs, aetosaurs, early dinosaurs, and other assorted Late Triassic animals that appear to have perished in a wildfire sometime between 210 and 212 million years ago. The NMMNHS has made several excavations at the Quarry since it was first discovered in 1998, but its dense layer of exquisitely preserved, shiny black fossils holds promise for many seasons of fieldwork to come.

Base Camp (the Quarry is just off to the left of the picture)

Early last Monday morning, I met with Senior Preparator Larry Rinehart (who organized this outing), Geoscience Collections Manager Justin Spielmann, Volunteer Preparator Dee Wilke and her husband Rich (who, as camp cook, kept us fat and happy the whole time). We headed north out of Albuquerque towards Abiquiu. Two-and-a-half hours later we arrived at the site, set up camp, and took a short walk up to the Quarry. New Mexico’s summer monsoon rains had washed a layer of brown sludge over the site, and we set to work clearing it away—an activity, it was noted, that resembled nothing so much as mining chocolate mousse.

Composite photo showing Justin Spielmann clearing mud from the Snyder Quarry, 7/30/2007

By early that afternoon, we had cleared out the mud and set up dams and channels to divert future rains (which, thankfully, did not come while we were working). Following that, we set to the main tasks at hand: reinforcing the plaster jacket around a large (5.5 x 3 foot) fossil block that was left behind during an excavation earlier this year, and quarrying fossils from the area surrounding the block.

Digging up fossils at the Snyder Quarry was a very satisfying experience. The siltstone surrounding the fossils was light grey and soft and fairly easy to pick away from the harder, blackish fossils, which were plentiful enough to find without too much effort. But there were a couple of challenges for a novice bonepicker like myself to overcome. First, the fossil layer contains not only blackish fossils, but blackish charcoal and blackish mineral stains as well. These sent me on a few wild goose chases into the rock before I learned how to discern the difference.

Second, while the fossil bones at the Snyder Quarry are generally disarticulated (that is, disconnected from the adjoining bones in its original owner’s skeleton), they are so abundant that it was difficult to isolate one fossil without running into at least three more. This was not exactly a horrible state of affairs—after all, we were hoping to collect as many meaningful bits of bone as we could. But it did quickly increase the size of several of the blocks that we ended up jacketing to bring home. For example, I began chasing the rock away from a lovely little metatarsal less than 2 inches long and after running into an ulna, a vertebral centrum, and a handful of less identifiable bits, we ended up jacketing a block nearly 2 feet square. It became very easy to see how the last crew ended up with a massive, one-ton jacket.

Stay tuned for the next installment: Bring ‘em Back Intact.

—Matt Celeskey.

File under: Dinosaurs, Reptiles, The Day Job, Triassic.

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…to The Boneyard. The second edition of this paleontology carnival is up at Laelaps, full of fossiliferous writings from around the web.

—Matt Celeskey.

File under: Miscellany.

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