Fossil Safari: Cleveland-Lloyd Quarry

Two buildings cover the bonebed

Beds rich in fossils are very rare.  In a very few places, conditions preserve the fossils in such detail that things such as pigmentation, three dimensional structure and cellular structure can be seen.  These areas are called Lagerstätten or Konservat-Lagerstätten.  And they always seem to be way out in the middle of nowhere.  Is that really necessary?  As you can tell by the picture to the left, the Cleveland-Lloyd Dinosaur Quarry in Utah is no exception.  It contains the densest concentration of Jurassic dinosaur fossils found anywhere in the world.

It is also noteworthy in the

Bones situated where they were found in 3D-space

abundance of carnivorous dinosaurs.  About 2/3 of the dinosaur fossils found are of theropods, mostly the apex predator Allosaurus fragilis.  Sauropods, the big long-necked dinosaurs like Brachiosaurus, Camarasaurus, and Barosaurus, are found to a lesser extent.  Ornithischians like Stegosaurus are also represented in the bone bed.  To date, over 12,000 bones have been collected and accessed into museum collections.  The Utah Museum of Natural History, University of Utah, Brigham Young University and Princeton University are major excavators of this bonebed, which is now a National Natural Landmark administered by the Bureau of Land Management.

Students excavating on site

Two buildings now cover the part of the bonebed with the densest concentration of dinosaur bone.  This protects the site from sunlight, weather, bone poachers and vandals.  It also makes excavation conditions right tolerable in the summertime.  Excavations are still taking place and bones are uncovered, removed for study and then some are returned for display in the place and orientation in which they were discovered.  When we were there, two college students were working on excavations and acting as interpreters of the bone barn.  Walkways allow the visitors to look over the bonebed without actually touching the surface.

When you study fossils from a

Walkway and bonebed

particular location long enough, you start to be able to identify where they are from by their coloration.  The Cleveland-Lloyd Dinosaur Quarry fossils are recognizable by their beautiful black color.  This is due to the unique blends of minerals found at the location during the time that the bone bed was formed.  This fossil bed is in the Upper Jurassic Morrison Formation (156-147 million years old).  Specifically, this bed is in the Brushy Basin Member, which is mostly mudstone made from volcanic ash.  Braided rivers flowed from the west into a basin, forming Lake T'oo'dichi' (Gesundheit).  This lake would have been salty and alkaline, much like modern Great Salt Lake.

Allosaurus fragilis maxillary, vertebrae and chevrons

Exactly why this fossil bed is here and why it contains the mix of organisms that it does.  It is very rare for a fossil assemblage to contain more carnivores than it does herbivores.  One idea is that as seasonal droughts set in, ground water would turn the volcanic ash into mud, trapping dinosaurs that came in for a drink.  Packs of young carnivores may have found the temptation to scavenge an easy meal great, especially as the smell of rotting meat increased.  The predators would then become mired in the mud and eventually die of starvation.  A competing hypothesis is that this low spot would be one of the last surviving watering holes and that the carnivores came here to hunt herbivores.  After the supply of herbivore meat was exhausted, the carnivores turned on each other and those left eventually died around here as the result of drought conditions.

Why do we have to be out in the sticks/BFE?

Mostly theropod bones

To have a really good fossil location you first have to have access to exposed rocks of the proper age. The more extreme the climate, the more that physical forces such as cycles of freeze/thawing and erosion can break down sediment and expose fossils. The fossil hunter also has to be at the location at the time that the fossil is exposed and collect the fossil. The ideal area is not impacted greatly by human activities than can destroy the fossils. Fossil sites are often exposed by construction, but paleontologists are usually given a very short time frame to come and remove fossils before the construction project resumes. I have seen more than one Pennsylvanian-era fossil forest fall to the bulldozer in Kansas City.

Long time working

It is likely that dinosaur bones were found by farmers as they drove livestock through the area.  The first organized excavation of record was conducted by F.F. Hintze and the Geology Department of the University of Utah in 1927.  A crew from Princeton University worked the quarry for the 1939-1941 field seasons under W.F. Stokes.  The quarry was idle until 1960 and a variety of institutions have conducted field work there since, including the Utah Museum of Natural History, the University of Utah and Brigham Young University.

Allosaurus fragilis arm

The Cleveland-Lloyd Dinosaur Quarry was named a National Natural Landmark in 1965.  The Bureau of Land Management established its very first visitor center on the site in 1968.  A new visitor center has since been constructed and opened in 2007.  This new visitor center is run entirely on electricity gathered using rooftop solar panels.  The visitor center houses exhibits detailing the history and geology of the site.  An excellent mounted Allosaurus skeleton is exhibited here.  If you like dinosaurs and are looking for something a little bit different, this is a nice drive and worth the effort.

Getting There

From I-70, turn north onto UT-10.  Turn right (east) onto UT-155 and go into Cleveland, UT.  If you feel like you have to take a relief break, Cleveland is your last chance at comfortable facilities for about an hour.  In Cleveland, turn right (south) onto S. Center Street/CR-204 (1.5 mi).  Turn left (east) onto S. Flat Bus Loop (0.3 mi), then slightly right onto CR-208 (1.4 mi), then continue onto CR-206 (2.1 mi).  Turn left (north) onto Vicor Reef Rd (4.0 mi).  Turn right onto Dinosaur Quarry Rd/CR-216 (5.1 mi) and then turn slightly left onto the road to the Cleveland-Lloyd Quarry Visitors Center (1 mi).  You are there.  Good luck getting back; hope you left some breadcrumbs.

Waypoint: Latitude 39.324019 N; Longitude 110.687683 W