Field Studies in Utah - Handout
FIELD STUDIES IN UTAH
BY
Dwayne D. Stone, Professor Emeritus of Geology, Marietta College
and
Edward L. Crisp, Professor of Geology, West Virginia University at Parkersburg
MORRISON FORMATION
One hundred and fifty million years ago the future Africa had already separated from the future USA by plates diverging
from the Mid-Atlantic Ridge (Figure 1). Note where future India and Antarctica are located. Dinosaurs could travel from one
future continent to another until land areas became more separated.
Figure 1. Paleogeography of the Earth during Late Jurassic time showing position of continents, oceans, and seas (From
Scotese, C. R., 1997, Pangea Begins to Drift Apart: http://www.scotese.com/late1.htm).
The Morrison Formation was named after outcrops in the vicinity of Morrison, Colorado (near Denver). Outcrops of the
Morrison Formation are present in parts of Colorado, Utah, Arizonia, New Mexico, Oklahoma, Nebraska, South Dakota, North
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Dakota, Wyoming, Idaho and Montana (see Figure 2).
Figure 2. Late Jurassic paleogeography of the southwestern U.S. showing the Morrison Alluvial Plain. Slightly modified
from: Blakey, Ronald, 1997, Images from 1997 GSA talk (Blakey, Ronald C. 1997, PALEOGEOGRAPHIC EVOLUTION OF
THE PASSIVE-MARGIN TO ACTIVE-MARGIN TRANSITION, EARLY MESOZOIC, WESTERN NORTH AMERICA: Geol. Soc.
Amer. Abs. with Progs) at http://vishnu.glg.nau.edu/rcb/paleogeogwus.html.
The sedimentary rocks are conglomerates, sandstones, mudstones (and shales) and limestones (mainly micrite) representing
terrestrial (land) environments. Coals from swamps are rare and there are no marine beds in the formation. The environments
of deposition include rivers (meandering and braided) with floodplains and lakes. Volcanism occurred during the deposition of
the Morrison and much of the volcanic ash is mixed with muds of the mudstones. Upon weathering the mudstone outcrops
with ash form a popcorn-like surface. Concretions are scatterred in the mudstones and many are comprised of gray, very heavy
barite (barium sulfate, BaSO4). Carbonate nodules, developed as calcium carbonate (CaCO3), were precipitated in ancient soils
of the Morrison. The Morrison rocks are gray, green, pink, white, yellow, purple, violet, brown and reddish brown (see Figures
3 and 4). Much of the coloration is due to iron minerals such as limonite (Fe2O3. nH2O) (yellow) or hematite (Fe2O3) (purple
and reddish brown).
The fossils of the Morrison Formation include both plants and animals. Plants were no doubt very plentiful in the warm
moist environment but most have not been preserved. There are some logs and leaves along with pollen and spores and the
sand-sized charophyte oogonia from green algae that lived in the lakes and rivers. Lush vegetation must have been present to
support the huge plant-eating dinosaurs that were present.
The invertebrate animals include coiled snails, lake and river clams that are sometimes four inches long, concostraceans
(arthropods) and ostracodes (more arthropods). All are small to microscopic except the clams (bivalves). Other invertebrates,
such as insects, were present but are rare.
The vertebrates include fish (lungfish in burrows), frogs, salamanders, lizards, crocodiles, turtles, and small mammals, but
all are scarce. Dinosaurs are the most plentiful vertebrates.
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Figure 3. Near horizontal strata of the Morrison Formation near Cleveland, Utah.
Figure 4. Dipping strata of the Morrison Formation at Dinosaur National Monument near Vernal, Utah.
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STRATIGRAPHY OF THE PERMIT AREAS
The rocks that you will see during the Utah Dinosaur Expedition in May of 2000 are diagramed below (Figures 5 and 6).
The Morrison Formation is 500 to 1,000 feet thick in this region.
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Cedar Mountain Formation - Lower Cretaceous (120,000,000 years old) - nonmarine.
❍ Mussentuchit Member - gray mudstone, thin sandstone.
❍ Ruby Ranch Member - gray and green mudstone with abundant irregular carbonate nodules that may cover some
slopes. Paleosols.
❍ Buckhorn Conglomerate Member - low cliff-forming hard gravel-rich brown distinctive unit with chert pebbles.
Some pebbles have Paleozoic corals. In some places contains silicified plant fragments.
Morrison Formation - Upper Jurassic (but may be Lower Cretaceous near the top) (150,000,000 years old) nonmarine.
❍ Brushy Basin Member - multicolored mudstones, thin brown limestones, brown discontinuous sandstones. This
unit has most of the dinosaur bones.
❍ Salt Wash Member - noted for thick brown sandstones and minor amounts of mudstones.
The two younger members of the Cedar Mountain Formation were named in 1997 by Kirkland and others. All of the above
have dinos but bones in thick sandstones and conglomerates are usually too difficult to remove.
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Figure 5. Generalized stratigraphic section of most of the Jurassic and Cretaceous rocks that will be present in our study area.
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Figure 6. Measured stratigraphic section at Theropod Coprolite locality east of Ferron, Utah.
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Figure 7. Paleogeography of Utah during Late Jurassic (top), areal extent of the Morrison Formation (left), and stratigraphic section of
east-central Utah.
Figure 8. Cross-bedding in a Morrison sandstone unit with horizontal bedding in the pebble conglomerate above the hammer (Photo by
E. L. Crisp, May 1999).
Figure 9. Molds of freshwater clams in a fine sandstone of the Morrison Formation (Photo by E. L. Crisp, May 1999)
DINOSAUR BONES OF THE MORRISON FORMATION
Dinosaur bones are black, blue, red-brown, gray or pitch black. They have been replaced(chemical exchange of calcium
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phosphate by iron minerals, silica, or other minerals) and permineralized (the filling of the tiny bone cavities [pores] by
minerals). The permineralized portion will appear as specks that may have several colors in the same broken bone. Some
bones retain their original outlines and will be in the form of small particles, owing in part to weathering (freezing and thawing)
or the action of rootlets near or at the outcrop for many years. Many bones deeper in the rock may be more intact but
practically all the bones are broken (or cracked). Some dino bones, even leg and large vertebrae, are crushed. These were
probably not replaced or permineralized until hundreds of feet of overlying sediments accumulated. The downward pressure
distorted the bones. Others will retain their original cross-sections and are unsquished. Replacement and permineralization
probably occurred "rapidly" before too many overlying sediments were deposited. Do keep in mind that these Morrison bones
were covered by at least a mile of sedimentary rock before mass movement and erosion exposed them at the outcrops today.
Mentally trace some of the Morrison rocks across the valleys from one hill to another. Visualize all the dinos that might
have been in these rocks. Their former locations are now represented by air. Such a sad thing. Think about the appearance of
a 2000 hillside a few thousand years into the future, with "new" dino bones sticking out of the rocks. We're pretty lucky to be
here in Emery County, Utah, and see the dinos that will vanish in the future if left uncollected.
DINO TRACE FOSSILS AND OTHER RARITIES
In addition to normal dino bones be on the lookout for possible:
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1. Footprints or trackways. Many show that three toes touched the ground but other dinos had four or five toes.
These can occur as depressions (external molds) on the original tops of sands (now sandstones) or as fillings (casts)
that will project downward from a bed, again usually sandstone. Most of the tracks made in mud are not preserved so
we can gaze down at them.
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Figure 10. Theropod footprint near Moab, Utah in the Salt Wash Member of the Morrison Formation (Photo by E. L. Crisp, May
1999).
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Figure 11. Iguanodontid footprints (upper part of photo) and a small theropod footprint (lower) in the
Cretaceous Dakota Sandstone near Morrison, Coloroado (Photo by E. L. Crisp, October 1999).
2. Poop. The old turds are called coprolites and some from the big plant eaters would have been gigantic. They will
probably appear at first to be concretions and the original shapes have probably been distorted. Perhaps some
carbonized plants will be present. Allosaurus (and other theropod) potty should have bits of bones and teeth. During
May of 1999 Dr. Stone found two large theropod coprolites in the Brushy Basin Member of the Morrison Formation and
during August of 1999 we removed one of those for transport back to Marietta College. The main body of this coprolite
was 5 feet long. It is the oldest and largest theropod coprolite ever found.
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Figure 12. Drs. Stone and Crisp with main body of theropod coprolite, August 1999 near Ferron, Utah (Photos by E. L.
Crisp, August 1999)
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Figure 13. A chunk of theropod coprolite from the Brushy Basin Member of the Morrison Formation. Note the bone
fragments. Found by Debbie Summerville, May 1999 near Moore, Utah (Photo by E. L. Crisp, April 2000).
3. Skin imprints. Visualize the surface of a modern lizard or crocodile. Irregular branching and joining lines or
semicircular spots close to a bone on the mudstone or sandstone might be the external mold of dino skin.
4. Eggs. Many dino eggs are elongate and several inches in length. They occur as clutches of six or more or as egg
fragments on the surface of the ground.
5. Nests. Dino egg nests will in cross-section view be depressions that can be several feet across. Some constructed a
circular high ridge around the central depression. It would be nice to find eggs in a nest.
6. Tooth marks. A lenticular hole like
would have beeen made in a bone by one Allosaurus or Ceratosaurus
tooth. Scratch marks were created by numerous teeth abrading a bone.
7. Pathologic bones. These are bones that were broken while the animal was alive and then healed by additional
calcium phosphate. These may appear as swellings. During intercourse (also known as having sex) bones, such as the
ribs of females, might have been injured by the front legs of a panting male. Dr. Stone can draw a picture of this
event. Occasionally a carnivores tooth has been found embedded in a repaired bone with calcium phosphate added to
this foreign object.
If you find what appears to be footprints, poop, skin imprints, eggs or nests, do NOT remove or dig into them.
Show the sites to your leaders. The same is true for a skull with teeth. Do NOT attack it - get HELP!
DINOSAURS OF THE MORRISON FORMATION
Figure 14. Skull of Camarasaurus in the Morrison Formation at Dinosaur National Monument (From: http://www.discovery.
com/exp/fossilzone/park-dinonatmon.html).
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The Late Jurassic Morrison Formation contains a diverse assemblage of dinosaur remains. Some of the largest dinosaurs
that ever lived (sauropods) are represented in Morrison deposits (see the skull of Camarasaurus in Figure 14). Also some of
the smaller dinosaurs that existed are represented in the Morrison Formation (example: Dryosaurus, adult length 4 to 6 feet).
The world famous Cleveland-Lloyd Dinosaur Quarry near Cleveland, Utah (see Figure 15 for quarry location) (where Dr.
Stone worked three summers during the 1960s when he was a graduate student in paleontology at the University of Utah under
the direction of James Madsen - see Figure 16) has rendererd about 10,000 bones of Morrison dinosaurs, ninety percent of
these belonging to the theropod Allosaurus. Forty-four different individuals of Allosaurus are represented in the bones at the
Cleveland-Lloyd Dinosaur Quarry. Several other Morrison dinosaurs have also been found there, including two theropods that
have not been found anyplace else, Marshosaurus and Stokesosaurus. The other major Utah dinosaur quarry in the Morrison
Formation is at Dinosaur National Monument. Figures 17 and 18 show the dinosaurs that have been found in the Morrison
Formation at Dinosaur National Monument near Vernal, Utah.
Figure 15. Location of Cleveland-Lloyd Dinosaur Quarry in Emery County Utah. Note the position of the WVUP and
Marietta College 2000 exploration areas. These areas are roughly on strike with the Upper Jurassic Morrison Formation
(Brushy Basin Member) rocks that are found at the Cleveland-Lloyd Dinosaur Quarry (Slightly modified from: Madsen, 1976).
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Figure 16. Dwayne D. Stone (left) taking a measurement on the floor of the Cleveland-Lloyd Dinosaur Quarry in the 1960s and
James H. Madsen Jr. (right) displaying an Allosaurus skull reconstructed by him from bones of the Cleveland-Lloyd Dinosaur
Quarry (from: Stokes, 1985).
MORRISON FORMATION DINOSAURS FOUND AT DINOSAUR NATIONAL MONUMENT
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Figure 18. Common Ornithischian dinosaurs and Theropods (Saurischians) from the Morrison Formation (From: U.S. Park
Service, Dinosaur National Monument, at http://www.nps.gov/dino/dinos.htm).
The following is a section from the website (http://www.ugs.state.ut.us/dinojur.htm) of the Utah Geological Survey
describing the dinosaurs of the Morrison Formation:
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Utah Geological Survey - Dinosaurs and Fossils
Jurassic Dinosaurs of Utah
The Morrison Formation
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Allosaurus, Utah's State Fossil, was the dominant predator of North America during the
Late Jurassic. It is known from numerous skeletons, ranging from 10 to 40 feet in length,
from the Cleveland-Lloyd Dinosaur Quarry in east-central Utah. Mounted skeletons, cast
from Cleveland-Lloyd Allosaurs, are displayed in over three dozen museums around the
world. With sharper teeth and a more graceful build, Allosaurus rivals Tyrannosaurus rex
as the supreme meat-eater of the Mesozoic.
Apatosaurus is the correct name for the dinosaur better known as Brontosaurus.
Apatosaurus is probably the most commonly known, but not the most common of the
four-footed, long-necked sauropod dinosaurs. This heavily built quadrupedal giant of the
Jurassic Period weighed more than 30 tons, or as much as six average elephants. With
lengths approaching 90 feet, the Apatosaurus was a giant in the Age of Dinosaurs.
Barosaurus was a slender, long-necked, long-tailed sauropod. Because of its graceful anatomy, some paleontologists have
argued that this sauropod could stand on its hind legs and reach high into the trees for food, perhaps to heights of 50-60 feet. A
skeleton from Dinosaur National Monument was mounted in the standing position was recently unveiled at the American Museum
of Natural History in New York. However, recent studies of its skull and neck suggest that with its close relatives Apatosaurus
and Diplodocus,Barosaurus spent most of its time grazing low growing plants.
Brachiosaurus was the largest and heaviest dinosaur known from the Morrison Formation
of Utah. This supergiant weighed as much as 80 tons, or the combined weights of 15 large
elephants. Ultrasauros, a supergiant from the Morrison Formation of Colorado was a giant
specimen of Brachiosaurus, and may have weighed as much as 100 tons. Brachiosaurus
is the giraffe-necked sauropod, with tall front legs and a long neck designed to reach far
above the ground. Bones of this Late Jurassic giant have also been found in eastern Africa.
Camarasaurus was the most common dinosaur of the Jurassic Period. Even with their
relatively short neck and tail, this sauropod reached lengths of 50 feet and weighed as much
as 25 tons. The spoon-like teeth chopped coarse vegetation (primarily conifers, cycads,
and ferns), their principal food.
Camptosaurus was a medium-sized, bipedal herbivore of the Late Jurassic that weighed up to 1,000 pounds and reached
lengths up to 23 feet. This ornithopod was ancestral to many of the highly successful plant-eating dinosaurs of the Cretaceous,
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such as the duckbills and Iguanodon.
Ceratosaurus was a large but slender predator of the Late Jurassic. With a strange horn
on the top of the head between the eyes, this active meat-eater may have engaged in head-butting combat. Like Brachiosaurus,
bones of Ceratosaurus have also been found in eastern Africa.
Diplodocus, the "double-beam" dinosaur named for unusual support structures beneath its
tail, was a long and slender relative of Apatosaurus. Several nearly complete skeletons
have been found at Dinosaur National Monument. Casts of Diplodocus skeletons,
averaging 87 feet in length, were sent to museums around the world by Andrew Carnegie in
the early part of this century, including the Vernal Field House of Natural History.
Dryosaurus is a common, small ornithopod first found at Dinosaur National Monument.
Dystrophaeus is the rarest, oldest, and first-discovered sauropod dinosaur in western
North America. Its bones were found by the Macomb Expedition to southern Utah in
1857. Because of its stratigraphic position at the bottom of the Morrison Formation
(Tidwell Member), this dinosaur may be ancestral to some or all of the other North
American sauropods of the Late Jurassic Morrison Formation.
Marshosaurus is another small, rare theropod. It reached lengths up to 16 feet and was named after O.C. Marsh, a famous
paleontologist from the 1800s.
Stegosaurus, the plated dinosaur, was one of the major plant-eaters of the Jurassic Period.
Most paleontologists believe its triangular bony plates were set in two rows along the
backbone in a staggered arrangement. The function of the plates is controversial. Perhaps
they were for protection, but some paleontologists think that they may have collected solar
radiation for thermal regulation. Even though it is the state dinosaur of Colorado, it is
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common in Utah.
Stokesosaurus was a rare carnivorous dinosaur reaching lengths of 13 feet, and was named for a prominent Utah geologist,
the late Dr. William Lee Stokes. Its bones and braincase anatomy indicate that it may be an ancestor of the gigantic
Tyrannosaurus that lived 85 million years later at the end of the Cretaceous Period.
Torvosaurus is the largest Jurassic theropod known in Utah. Reaching nearly the size of
Tyrannosaurus, it was able to terrorize even the giant sauropods. Although rare it is known
from a couple of sites.
CLASSIFICATION OF MORRISON DINOSAUR GENERA
The following is one classification scheme with the Morrison Formation dinosaur genera:
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Phylum Chordata
❍ Class Reptilia
■ Subclass Diapsida
■ Infraclass Dinosauria
■ Superorder Saurischia
■ Order Theropoda
■ Genus Allosaurus
■ Genus Ceratosaurus
■ Genus Ornitholestes
■ Genus Coelurus
■ Genus Stokesosaurus
■ Genus Marshosaurus
■ Genus Torvosaurus
■ Order Sauropodomorpha
■ Genus Camarasaurus
■ Genus Apatosaurus
■ Genus Brachiosaurus
■ Genus Diplodocus
■ Genus Haplocanthosaurus
■ Genus Barosaurus
■ Genus Seismosaurus
■ Superorder Ornithischia
■ Order Thyreophora
■ Genus Stegosaurus
■ Order Ornithopoda
■ Genus Camptosaurus
■ Genus Othnielia
■ Genus Dryosaurus
Dinos are divided into two superorders based on the arrangement of the pubis and ischium bones in the hips. Portions of the
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two bones are nearly parallel in Ornithischian dinosaurs (see Figure 19 below).
Figure 19. The Saurischian hip structure (left) and the Ornithischian hip structure (right) (from: Poling, Jeff at http://www.
dinosauria.com/dml/dmlf.htm).
In addition to the hip structure, all Ornithischian dinosaurs have a predentary bone in the lower jaw of the skull which is not
present in the Saurischians (see Figure 20 below).
Dromaeosaurus
Edmontosaurus
Figure 20. A Saurischian skull (right) and an Ornithischian skull (left) (from: Poling, Jeff at http://www.dinosauria.com/dml/
dmlf.htm).
Using cladistics we could show the major groups of dinosaurs as a cladogram (Figure 21). Cladograms show hypothetical
evolutionary relationships based on shared derived characters within a group.
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Figure 21. Major groups of dinosaurs (from: Poling, Jeff at http://www.dinosauria.
com/dml/clado/dinosauria.html).
A cladogram of the Saurishia is shown in Figure 22 below.
Figure 22. A cladogram of the Saurischica (from: Messing, Charles G, 2000, http://www.nova.edu/ocean/biol1090/W10CJURALIFE2.htm).
One interpretation of the relationships of the Sauropodomorpha is shown in Figure 23. In this
interpretationCamarasaurusandBrachiosaurus are in the family Brachiosauridae and Diplodocusand Apatosaurus are in the
family Diplodocidae. Some paleontologists separate the family Camarasauridae from the Brachiosauridae (as shown in Figure
22 above).
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Figure 23. Major groups of Sauropodomorpha. Characters are - 1, small head and peg-like teeth (and elongated cervical
vertebrae); 2, addition of extra cervical vertebrae to the neck; 3, apron-like pubis; 4, fore limbs as long as or longer than hind
limbs, making the back slope posteriorly; 5, teeth restricted to front of mouth; 6, armor. (from: Olsen, Paul, 2000, http://
rainbow.ldeo.columbia.edu/courses/v1001/morisson14.html).
A general cladogram of the Theropoda is shown in Figure 24. In this cladogram Ceratosaurus would be placed in the
Ceratosauria, whereas most of the other Morrison genera (except Ornitholestes) would be placed in the Carnosauria.
Theropods such as Tyrannosaurus and kin would be placed on a branch between Ornitholestes and Deinoychosauria.
Cretaceous theropods such as Deinonychus and Utahraptor would be placed in the Deinoychosauria.
Figure 24. Cladogram of Theropoda (from Olsen, 2000).
1. three-toed foot
2. digits IV and V lost on hand
3. long arms
4. semilunate carpal
5. fused pelvis
6. large hole in lacrimal bone in skull
7. ?no unique derived characters?
8. giant, hook-like claw on digit II of pes
9. flight feathers
Figure 25 is a cladogram of the Ornithischia and shows the position of Stegosaurus in the group Stegosauria. The three
Morrison ornithopods, Dryosaurus, Camptosaurus, and Othnielia would be placed in the Iguanodontia, however, some
paleontologists would place Dryosaurus and Othnielia intermediate between Hypsilophodontidae and Iguanodontia.
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Figure 25. Cladogram of the Ornithischia (from: Messing, Charles G., 2000, http://www.nova.edu/ocean/biol1090/W10DJURALIFE3.htm).
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