Mark Wilson June 10th, 2012
These rounded stones are labeled in our collections as gastroliths (literally “stomach stones”) from Starr Springs near Hanksville, Wayne County, Utah. I’m featuring them this week in honor of our Utah Project team working right now in the baking Black Rock Desert near Fillmore, Utah.
From their reported location, these stones are likely out of the Summerville Formation (Middle-Upper Jurassic) and, in another plausible supposition, probably from some sort of dinosaur. Sometimes we just have to trust the labels on our specimens, at least for educational purposes!
My friend Tony Martin recently wrote an excellent blog post on gastroliths, so I won’t repeat his insights here. The general wisdom is that these stones were consumed by herbivorous dinosaurs to aid in their digestion. They would have lodged them in the equivalent of a gizzard and used them to grind their food, much like modern birds. (And yes, dinosaurs were birds themselves.) Gastroliths usually have a resistant lithology to be useful as grinders. The gastroliths above are chert, one of the hardest rock types.
Identifying gastroliths correctly is a bit of a challenge if you don’t find them inside a dinosaur skeleton. The most common indicators are that they are very smooth, are in a location where they were unlikely to have been transported inorganically, and are of a lithology unlike the surrounding rock (“exotics” as geologists like to call them). Still, even with all these criteria met, we must be a tad suspicious if we didn’t find them associated with dinosaur bones. I would never, for example, buy a gastrolith in a rock shop. Without context, it could be just a stream-worn stone. I’m trusting the label on ours that we have the real deal!
Stokes, W.L. 1987. Dinosaur gastroliths revisited. Journal of Paleontology 61: 1242-1246.
Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52: 1-16.
mpollock June 8th, 2012
FILLMORE, UTAH – [Guest Bloggers Matt Peppers and Will Cary]
On the morning of the 8th, all seemed well. Much like days before, we all arose and began to pack our lunches for the day. However, as we piled into the car, an ominous light started to blink on the dashboard. Low tire pressure. Concerned, Dr. Judge pulled us into a nearby gas station and checked the tires. Much to our dismay, the left rear tire was 10 psi lower than it should be, a repeat occurrence from a few days earlier. Not wanting to jeopardize our upcoming Mystery Fun Day, Drs. Judge and Pollock made the decision to take the car into a repair shop to have the problem diagnosed. While they were gone, they left us to wreak havoc upon the KOA Kampground. We started by swimming and relaxing by the pool, and ended by swimming and relaxing by the pool. All before lunchtime. We retired to our individual cabins to enjoy the lunches we had packed a few hours earlier in glorious air conditioned komfort.
Around 1 pm, the professors returned and it was business as usual. Even though we had lost half of our day to a small hole in the tire (curse you, basalt!) we rushed out to mob Kevin’s project for the afternoon. Arriving on the cinder cone at peak temperature made for a challenging work environment (especially after having spent most of the day in a sun-induced stupor) but we turned the afternoon into a very productive, albeit rushed, day. After reviewing the wall Kevin had used to map his xenoliths, we spread out and tried to collect as many of the 16 different types as we could find. After a few small injuries, stumbles, artistic work with a rock hammer, and some sore hands trying to pry the xenoliths out of the uncooperative host rock, we amassed a small mountain of samples for Kevin. As Whitney struggled to bag and record the samples in the gusting wind, the rest of us made one last sweep of the area for any xenoliths to claim.
We trooped back down the van, and made the dusty trek back to the kampsite, just in time to shower and recover before we left for dinner at six. After a quick stop to pick up a package containing some hardier field notebooks we went of to dinner followed by a stop for ice cream, where the professors revealed the Fun Trip they had planned for Saturday. We will be driving down to Bryce Canyon on the morrow to spend the day in the park. None of us have been there, so it promises to be a unique experience for us all!
mpollock June 7th, 2012
FILLMORE, UTAH – What do volcanic bombs, xenoliths, and giant gypsum crystals have in common? Not much, except that we saw them all during our long and productive day. We met to pack lunches at 7:30 am and finished with student-faculty meetings at 10 pm, so we’re all ready for a good night’s rest, but we thought we’d give you a quick update on our progress.
Although it was long and challenging, the cool temperatures and partly cloudy skies made for a pleasant day in the field. Back to the lava fields tomorrow to check out some scarps and map flow boundaries. Wish us luck!
mpollock June 6th, 2012
FILLMORE, UTAH – Whitney and Matt took charge today, leading us on an investigation of the lava flows that extend westward from the Miter cinder cone.
We picked our way across the sharp, rubbly flow surface and learned the importance of careful observation. Although we weren’t looking for bombs and xenoliths, we found both along our path.
Whitney had a successful day of mapping the margins and morphology of a couple of complicated lava flows.
Matt’s productive day included finding a spectacular fault exposure, where he made lots of measurements on the fault and associated joints.
Overall, it was a strong start to the field project, despite the searing sun and blinding wind storm.
We were rewarded for all of our hard work.
We hope every day of our field season is just like this one (minus the wind).
mpollock June 3rd, 2012
FILLMORE, UTAH – [Guest bloggers Matt Peppers and Will Cary]
As Dr. Wilson so kindly stated in his last blog post, the Utah group arrived safely at Salt Lake City International Airport on Saturday, June 2. After stopping briefly at a Target to get various essentials, we finished our two-hour drive at Fillmore (see here for how the drive went), the town we will reside in for the next two weeks. We are staying at a KOA Kampsite in some kozy little kabins. After getting acquainted with the campsite layout, we explored some of the finer cuisine options, finally settling on Larry’s Drive-In Diner across the road. Will tried a marshmallow milkshake that gave him enough sugar to power through the jet lag associated with the time zone change. After a filling meal, the group headed back to the campsite for a quick group meeting to go over the schedule for Sunday, which promised to be an orientation day to the Black Rock Desert and what we could expect. Following the meeting, everyone felt the effects of travel and promptly retired to their respective cabins for the evening.
The next morning, the group met at 9:30 to pack lunches for the day followed by an overview of equipment and safety precautions that we would need for our fieldwork. With backpacks set up, we gathered as much water as we could carry and set out to our first meeting with the Black Rock Desert. We drove directly west out of Fillmore and, although we couldn’t get onto it, saw Ice Springs, our future field site. We drove around the flow front boundaries and were impressed by how distinct and steep the boundaries actually were. Because today was an orientation day, we set out to find some lava tubes in the Tabernacle Hill lava field. Although we were unsuccessful in locating them, we had some good experience using the GPS units. In addition, we spent a lot of time looking at pressure ridges in the lava field, which adds additional complexity to some students’ projects.
Admitting defeat in finding the lava tubes (and questioning the signage that lead us to that area), we drove on to White Mountain, a hulking mass of gypsum sand a few minutes away. Looking for a place to get out of the 93° heat to eat our lunches, we headed to the one tree we had seen in the entire trip. Stepping out of the car almost had us believing we were in the Bahamas, and the white sand proved a pleasant place to sit. As we moved under the shade of the tree, two small owls flew out from its branches. Waiting cautiously in the leaves above us were three more owls, who seemed upset that we interrupted their lunch with our lunch (3 dead mice taunted them from next to where we were sitting).
After getting back into the car, we asked Dr. Judge and Dr. Pollock what our next stop would be. Getting only a, “Classified” as a response, all we could do is bounce around in the back of the car down a dusty road. We were pleasantly surprised when the trip ended at a natural hot spring. We eagerly climbed out of the car and jumped in.
We continued our first full day by taking a quick stop back at the campsite for a change into dry clothes before heading to meet Dr. Wilson’s, aunt, Ms. Sylvia Huntsman. She graciously welcomed us into her house where we played with her two dogs, Zeke and Bogey and ate delicious apple cobbler. When eyes started to droop from too much time sitting in a comfortable air-conditioned house, we excused ourselves to go eat more food. The fine cuisine of Fillmore proved itself once again at the “Garden of Eat’n.”
The first day ended with a final meeting back at the campsite to set a schedule for Monday (the 7 am departure time was a harsh return to reality) and a beautiful sunset.
Mark Wilson August 14th, 2011
I’ve avoided having a trilobite as Fossil of the Week because it seems like such a cliché. Everyone knows trilobites, and they are the most common “favorite fossil” (invertebrate, anyway). Plus our best trilobite (seen above) is the most familiar trilobite of all: Elrathia kingii (Meek, 1870). One professional collector — just one guy — said that in 20 years he sold 1.5 million of these.
Still, trilobites are cool. They virtually define the Paleozoic Era, appearing in the Early Cambrian and leaving the stage (with so many others) in the latest Permian. They were arthropods, sharing this very large phylum with insects, spiders, crabs and centipedes. The name “trilobite” means “three lobes” referring to the axial lobe (running down the center along the length of the animal) and the two pleural lobes, one on each side. They also have three parts the other way: a head, thorax and pygidium (the tail end).
Elrathia kingii is a ptychopariid trilobite found in extraordinary numbers in Middle Cambrian dark shales and limestones. There is a geological story here, two of them, in fact. One reason they are so common is that their populations were commonly buried by sediment stirred up in massive storms (Brett et al., 2009). They are among the only fossils found in organic-rich dark sediments because they lived in the harsh “exaerobic zone” at the very minimum of oxygen needed for animal life (Gaines and Droser, 2003). They apparently were the first large invertebrates to exploit this marginal environment.
Elrathia kingii gives us the opportunity to meet a pioneering American paleontologist: Fielding Bradford Meek (1817-1876). He originally described this species in 1870, calling it Conocoryphe kingii (see above). Paleontologists are quite familiar with the name “Meek” following a fossil species because he described hundreds of them. Meek was a native of Madison, Indiana, a place where Ordovician fossils are abundant and easily collected. He was apparently an unsuccessful businessman so he jumped at a chance in 1848 to work for the U.S. government surveying the geology of Iowa. Meek was good at this job and soon was working with James Hall in New York, the country’s premier paleontologist. Meek was eventually based in Washington, D.C., with the United States geological and geographical surveys. After many accomplishments in government service, he died of tuberculosis in 1876 (White, 1896).
Brett C.E., Allison P.A., DeSantis M.K., Liddell W.D. and Kramer A. 2009. Sequence stratigraphy, cyclic facies, and lagerstätten in the Middle Cambrian Wheeler and Marjum Formations, Great Basin, Utah. Palaeogeography, Palaeoclimatology, Palaeoecology 277: 9-33.
Gaines, R.R. and Droser, M.L. 2003. Paleoecology of the familiar trilobite Elrathia kingii: An early exaerobic zone inhabitant. Geology 31: 941–944.
White, C.A. 1896. Memoir of Fielding Bradford Meek, 1817-1876. Biographical Memoirs, National Academy of Sciences, p. 75-91.
Mark Wilson April 17th, 2011
The technical term is ostreolith, but “oyster ball” is much more descriptive. These fossils are found by the thousands in the Carmel Formation (Middle Jurassic) in southwestern Utah. As far as I know, this is the only place they’ve ever been found. Colin Ozanne (’96) worked on these ostreoliths as part of his Independent Study project, and the results of our work were published in a 1998 issue of Palaios. Colin now, by the way, is an Engineer Trial Attorney for the US Army Corps of Engineers in Buffalo, New York.
Ostreoliths are “circumrotatory accumulations” of the little oyster Liostrea strigilecula. The most common form began with a clam shell fragment as a nucleus. Oyster larvae recruited on the top shell surface and grew in the normal way. A current, though, flipped the shell over, exposing the underside that was in turn encrusted by more oyster larvae. These grew into larger oysters until, again, the shell flipped back over. A new generation of oysters then encrusted the older layer. The shell then overturned again and … you get the idea. Some ostreoliths grew this way to almost a quarter meter in diameter. The cup-shaped left valve of Liostrea was an essential feature for ostreolith development. A typical flat oyster would not build the necessary depth with each layer.
Several sclerobionts (hard substrate dwellers) grew with the oysters on the ostreoliths, including the bivalve Plicatula, disciniscid brachiopods and cyclostome bryozoans. Mytilid bivalves also drilled holes (called Gastrochaenolites) in the oyster skeletons to form cavities for their filter feeding.
Ostreoliths, strange and unique as they are, tell us a lot about the depositional environment of the Carmel Formation. The sediments accumulated in these horizons under fairly high energy with periodic storm disturbances. The mytilid borings trapped ooids during formation of the ostreoliths, showing that this characteristic carbonate sediment was more common in the environment than indicated by the rocks alone.
Regardless of their scientific value, though, oyster balls certainly start good conversations!
Mark Wilson February 13th, 2011
This week we have a trace fossil that looks almost exactly like the animal that made it. A trace fossil is evidence of organism activity recorded in the rock record. The photograph above shows one of my favorite specimens: Asteriacites lumbricalis von Schlotheim 1820 from the Middle Jurassic (Bathonian) Carmel Formation in southwestern Utah. I collected it while doing fieldwork with Wooster student Steve Smail too long ago for either of us to mention.
This fossil was made when a brittle star (ophiuroid) burrowed into carbonate sediment to either hide from predators or to look for a bit of food. Brittle stars are echinoderms that appeared in the Ordovician and are still very much alive today (see below). This Jurassic trace was formed when a brittle star essentially vibrated its way down into the loose sediment in a manner many of their descendants do today. The result is what appears to be an impression of the body (an external mold) but is actually formed by action of the animal.
The trace fossil Asteriacites is far more common in the rock record than the brittle stars and seastars that made it. These traces thus often indicate the occurrence of organisms in critical intervals where they would otherwise be unknown. For example, Asteriacites lumbricalis is found in Lower Triassic rocks showing that brittle stars were part of the recovery fauna after the Permo-Triassic Mass Extinction (see, for a Wooster example, Wilson & Rigby, 2000).