• Vertebrate Paleontology in Utah (just in case it's not automatic, it starts on page 51. let me know if the link doesn't work! -jen)
    • "A vertebrate track site in the Navajo/Nuggest Sandstone (Upper Triassic - Lower Jurassic) on the shore of Red Fleet Reservoir near Vernal, Utah, includes more than 350 tracks of bipedal dinosaurs in nine distinct layers of horizontally bedded, calcareous sandstone. [The small tracks are Grallator, and the larger tracks are Eubrontes]" (Vertebrate Paleontology in Utah)


(LINKS!!! - Also see PDFs at top)
http://home.comcast.net/~theropod-archives/pdf/Camp_1936_UCalPubGeoSci_24(2)_39_NS.pdf
A New Type of Small Bipedal Dinosaur from the Navajo Sandstone of Arizona

http://geology.geoscienceworld.org/cgi/content/abstract/17/5/438
Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona

Paleontology Journal on Ammosaurus of Conn.


http://www.jstor.org/stable/pdfplus/1299922.pdf

http://ist-socrates.berkeley.edu/~irmisr/navajo.pdf
A REVIEW OF THE VERTEBRATE FAUNA OF THE LOWER JURASSIC NAVAJO SANDSTONE IN ARIZONA


http://www.geosciences.unl.edu/~dloope/pdf/APP08.pdf
http://books.google.com/books?hl=en&lr=&id=3Ta_uivXdrAC&oi=fnd&pg=PA284&dq=Crocodylomorphs,+navajo+sandstone&ots=YnUOBv-Jmx&sig=IsfRgrBlkItk_w7yIZQLQW0ApMg#v=onepage&q=Crocodylomorphs%2C%20navajo%20sandstone&f=false

http://gsa.confex.com/gsa/2001AM/finalprogram/abstract_19815.htm

http://www.ldeo.columbia.edu/~emmar/research/rainforth1997.pdf (This is a pretty good one, long but full of easy to understand info)

http://books.google.com/books?hl=en&lr=&id=1nZrbiUfMmMC&oi=fnd&pg=PA285&dq=Clark+and+Fastovsky,+1986&ots=FXFcPQHEQc&sig=dl4L46_8r6RibDICkHnurGLDT-c#v=onepage&q=&f=false (part authored by Fastovsky!)


Revision-Revision: ((Not organized or formatted yet))


Content for new revision:
(should we add a separate section to talk about sequences?)


Determining the Stage of the Navajo Sandstone
Dennis Titterton
Zoe Gentes
Jen Sullivan
Amy Lombari
Andrew Infante

ABSTRACT
The Navajo Sandstone is part of the Glen Canyon Group that is located in Utah, Colorado, Arizona, and New Mexico. To determine the stage of the sedimentary rocks comprising the Navajo Sandstone, we used biostratigraphy and lithostratigraphy. Body fossils are rare in the Navajo Sandstone, so we drew conclusions largely from the trace fossils consisting of trackways. Grallator, Eubrontes, Anchisauripus, Anomoepus, Trisauropodiscus moabensis, Dilophosauripus, Otozoum, Navahopus, and Brasilichnium were the ichnotaxa included in this report. ((this is very very rough… the paper needs to be written first…FOCUS: what is the stage of the Navajo Sandstone?))

INTRODUCTION
The Glen Canyon Group is a set of fluvial and eolian terrestrial sediments that is Early Jurassic in age (Olsen and Galton, 1977; Clark and Fastovsky, 1986), although the base of the group may be Late Triassic in age (Morales and Ash, 1993).
((Should we include figures? We could have gotten more points on the last paper if we included figures, and they will be included in the revision))
external image C:%5CUsers%5CZoe%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_image002.gif
FIGURE 1. Distribution of exposed Navajo Sandstone strata in Arizona and Utah. Modified from Winkler et al. (1991).

The Navajo Sandstone is widespread throughout much of northern Arizona and southern Utah. As part of the Glen Canyon Group, this unit represents the terminal record of the Lower Jurassic in the southwestern United States (Clark and Fastovsky, 1986; Winkler et al., 1991) that was part of a continuous “sand sea” that covered much of the western margin of North America (Blakey, 1994). Its vertebrate fauna is important for several reasons. First, this is the only record of a late Early Jurassic vertebrate fauna in North America and one of the only records of this time worldwide (Winkler et al., 1991). Second, the Navajo vertebrate fauna samples a unique arid desert fauna not represented by other coeval sediments of the Glen Canyon Group.

BIOSTRATIGRAPHY

Body Fossils
There is not an abundance of body fossils found in the Navajo Sandstone. Those that can be found there include a crocodylomorph, a few partial tritylodonts and prosauropods, and a small theropod (Rainforth 1997).
Tritylodontidae.—Winkler et al. (1991) described a single tritylodont specimen) from northern Arizona. This specimen is partially articulated and preserves most of the trunk skeleton including the pectoral girdle, forelimbs, dorsal vertebrae, pelvic girdle, and partial hindlimbs. Winkler et al. (1991) tentatively allied the specimen with Kayentatherium based on the presence of transverse expansions of the dorsal vertebral neural arches on the dorsal vertebrae. However, Sues et al. (1994) considered the specimen non-diagnostic and referred it to Tritylodontidae indet.
Crocodylomorpha.—Three crocodylomorph specimens have been reported from the Navajo Sandstone of northern Arizona. All specimens have been referred to the Protosuchidae, a group that as traditionally defined is probably paraphyletic, although the described Early Jurassic North American species are all included in a monophyletic clade (Pol and Norell, 2004; see Wu et al., 1997 for an alternate view of protosuchian monophyly). This referral is based mainly on the morphology of the preserved armor and the fact that the fossils are Early Jurassic in age (Rinehart et al., 2001)
Sauropodomorpha.—Brady (1935, 1936) was the first to report sauropodomorph body fossils from the Navajo Sandstone of Arizona. Although he considered the specimen to be a “primitive theropod” following contemporary established taxonomic schemes, he recognized its close affinities to specimens described by Marsh as members of the Anchisauridae, which are now known to be sauropodomorphs (Yates, 2004). The specimen consists of both pedes (Fig. 3), a poorly preserved fragmentary pelvis, portions of articulated caudal vertebrae, and several articulated gastralia. It has been published in the literature as MNA G2 7233 (e.g., Galton, 1971; Yates, 2004), although the specimen is currently catalogued and labeled as MNA V743 through MNA V752. Nevertheless, it is clear from the original description and figures that this constitutes a single specimen (Brady, 1935). Galton (1971) briefly described the specimen and referred it to Ammosaurus cf. A. major based on the similarity of the pes to the type material of Ammosaurus major. Galton (1976) reiterated his referral of the specimen to Ammosaurus and included additional descriptions and figures of the material. Yates (2004) recently revised Anchisaurus and Ammosaurus, and convincingly demonstrated that the two are synonymous. He further concluded that the MNA specimen represents an indeterminate sauropodomorph that does not display any synapomorphies of Anchisaurus.
Theropoda.—A partial theropod skeleton discovered by the Rainbow Bridge-Monument Valley Expedition of 1933 in northern Arizona (Hall, 1934) was described by Camp (1936) as a new genus and species, Segisaurus halli. This partially articulated specimen consists of portions of the vertebral column, much of the forelimb, partial pelvis, most of the hindlimb, and many gastralia (Fig. 5). Camp recognized that Segisaurus was distinct from other small carnivorous dinosaurs known at the time (e.g., Compsognathus and Ornitholestes), and named a new family, the Segisauridae.
Although the body fossil record of the Navajo Sandstone is poor, the variety of depositional environments that preserve vertebrate fossils indicates that at least some of these animals probably inhabited both dune and interdune environments. Extensive post-mortem transport is unlikely, because most specimens are associated and often articulated. The distribution of known vertebrate fossils, although not statistically significant, seems to suggest that future prospecting of the Navajo Sandstone for vertebrate fossils should focus on interdune and related facies. (Irmis)


"There are only a few body fossils found in the Navajo Sandstone. These fossils are of the Tritylodontidae, Crocodylomorph, Sauropodomorpha, and the Theropoda classifications."

This is all info from
  • Sauropodomorpha (suborder)
    • Ammosaurus (genus)
      • Closely related to Anchisaurus, to which it may actually be synonymous (Othniel C. Marsh, the man who identified Ammosaurus for the first time, confused it with Anchisaurus). It is actually more closely related to Plateosaurus.
      • Originally found in Connecticut during Pleinsbachian through Toarcian stages of Early Jurassic Period.
      • The fossil's holotype (a piece of a fossil that can be used to associate it with a taxon) was found. It was the rear half of the body fossil.
      • Was still found in Bajocian stage deposits in North America, which makes it one of a few genera that survived to the Middle Jurassic.

  • Theropoda (suborder)
    Segisaurus halli, as found. Click to view full size
    Segisaurus halli, as found. Click to view full size
    • Segisaurus (genus)
      • Segisaurus halli
        • First discovered by a local Navajo Indian/Native American who brought it to a local group of archaeologists on an expedition within the canyon. Other than this first discovery, no others specimens have been found.



Trace Fossils
((ICHNOFOSSILS or ICHNITES
(pronounced IK-nites) Also known as trace fossils or ichnofossils, these are fossilized footprints, nests, dung, gastroliths, burrow, stomach contents, etc., but not actual body parts. Ichnofossils record the movement and behavior of animals. Ichnology is the study of ichnites.
ICHNOGENERA
Ichnogenera (meaning "footprint group") are groups of dinosaurs whose characteristics are surmised only from their fossilized footprints. When dinosaur trackways are found, it is nearly impossible to determine which dinosaur genus made the prints, so the prints are given a new genus name, an ichnogenus.))
Some ichnogenera include:
Theropods (bipeds with relatively long, narrow toes ending in claws): Eubrontes (early Jurassic), Grallator (late Triassic), Carmelopodus (middle Jurassic), Anchisauripus (late Triassic to early Jurassic period), and Megalosauripus (late Jurassic). Theropod footprints range from a few inches long to about 3.3 feet or 1 m long).
Prosauropods:Tetrasauropus (late Triassic), Pseudotetrasauropus (late Triassic), Otozoum.
Sauropods (quadrupeds with 5-toed, elephant-like feet; the inner three or four toes had claws): Brontopodus. Sauropod footprints can be as big as a bathtub (about 6 feet or 2 m long).
Ornithopods (bipeds or quadrupeds with wider tracks with hoof-like claws): Anomoepus, Amblydactylus (a hadrosaur).
SOME DINOSAUR ICHNOGENERA… http://www.enchantedlearning.com/subjects/dinosaurs/glossary/Ichnogenera.shtml))


While body fossils are not very numerous in the Navajo Sandstone, a large amount of trace fossils can be found. Various ichnogenera have been discovered, representing up to 9 vertebrate families. Whilst the animals known from skeletal remains are represented by tracks, the ichnites suggest that large theropods, lizards, thyreophorans, and possibly basal ornithischians and pterosaurs also inhabited this environment” (Rainforth 1997).

Below is a list of the ichnotaxa known from the Navajo:
Grallator (pronounced GRAL-uh-tore) Grallator was a herding dinosaur known only from its fossilized footprints. The relatively common, three-toed tracks average about 7 inches (17 cm) long. The shape and pattern of the bipedal prints (including the ratios of the lengths of the toes) indicate that it was probably a small theropod (a bipedal meat-eater) similar to Coelophysis. The tracks date from about 200 million years ago, during the very late Triassic period to the early Jurassic period. Grallator trackways have been found in the USA (NJ, PA, CT), Canada, and Europe.
Eubrontes (pronounced you-BRONT-tees) Eubrontes giganteus is a dinosaur known only from its fossilized, three-toed footprints. Eubrontes means "true thunder." The sandstone tracks range from 10-16 inches (25.5-41 cm) long and they are spaced 3.5-4.5 feet (1-1.4 m) apart. These sizes indicate that the dinosaur who made the prints was about 5 feet (1.5 m) tall at the hip (about the size of Dilophosaurus). The shape and pattern of the prints indicate that it was a theropod, a bipedal meat-eater. The tracks date from about 200 million years ago, during the early Jurassic period. Eubrontes trackways were found in Connecticut, USA. Geologist Edward Hitchcock named them in 1845. No fossilized bones have been found in the vicinity, but over 2,000 tracks have been uncovered in what is now Dinosaur State Park. Eubrontes is the state fossil of Connecticut.
Anchisauripus (pronounced AN-key-SAWR-ip-us) Anchisauripus is an ichnogenus of dinosaur, a theropod dinosaur only known from fossilized, bipedal, three-toed footprints (roughly 4 to 7 inches long) from Connecticut, USA during the late Triassic to early Jurassic period. It was named by Lull in 1904.
Anomoepus. Anomoepus intermedius is a dinosaur known only from its fossilized tail prints; these prints are only a few inches long. It lived during the Triassic period. Anomoepus was named by E. B. Hitchcock in 1848. Fossils have been found in Holyoke, Massachusetts and New Jersey, USA.
Trisauropodiscus moabensis
Dilophosauripus
Otozoum
Navahopus
Brasilichnium

((Fastovsky: The above trace fossils are trace fossils assigned to body fossils. How was this determined (shape of bone, positions, etc)? What are the ages for these organisms (radiometric or otherwise)? How accurate is this?))


LITHOSTRATIGRAPHY
Ages of Kayenta Formation (below). Use Segisaurus halli and any radiometric dates.
Age of Caramel Formation (above). Fastovsky said it was marine. Again, how accurate are these dates.

REFERENCES
Rainforth, Emma C., 1997, Vertebrate ichnological diversity and census studies, Lower Jurassic Navajo Sandstone, Research Report submitted in partial fulfillment of the degree of Master of Science, Department of Geological Sciences, University of Colorado at Boulder.
Galton, Peter M., 1971, The Prosauropod Dinosaur Ammosaurus, the Crocodile Protosuchus, and Their Bearing on the Age of the Navajo Sandstone of Northeastern Arizona, Journal of Paleontology, Vol. 45, No. 5, pp. 781-795.
Faul, Henry, Wayne Roberts, 1951, New Fossil Footprints from the Navajo Sandstone of Colorado, U.S. Geological Survey.
Irmis, Randall B., 2005, A Review of the Vertebrate Fauna of the Lower Jurassic Navajo Sandstone in Arizona, Department of Integrative Biology and Museum of Paleontology.



((Okay... this is a lot of stuff. It is somewhat jumbled up because I haven't been able to sort through it all yet. But there is a lot of useful information in here regarding fossils from the Navajo. Now we just need how they radiometrically dated them, and then some other dates for the above and below formations, and I think we can have a good paper.
All of the stuff below is directly from the papers, so in using this, it needs to be cited properly.
Also, I think some of these papers disagree with each other... I'm going to try and see Fastovsky tomorrow to get facts straight.))


Good Searches:
Segisaurus halli
Crocodylomorphs
sauropodomorphs
Eubrontes
Grallator

Few significant fossil remains have been found in the great aeolian sandstones of the American west.
(Faul, 1951)
Very few skeletons of prosauropod dinosaurs have been found in North America, and most of these are from the Upper Triassic of the Connecticut Valley. An exception is the specimen described by from the Navajo Sandstone of north- eastern Arizona. Brady referred this specimen to Ammosaurus, a prosauropod genus hitherto known only from the Connecticut Valley. The Navajo Sandstone is an aeolian deposit that outcrops extensively in Utah, Arizona, Nevada, Colorado and New Mexico and reaches a thickness of at least 2100 feet in southern Utah. Only one other reptile has been described from this formation, the coelurosaurian dinosaur Segisaurus, but Dr. C. L. Camp also collected two undescribed partial skeletons, one referable to Ammosaurus and the other to the crocodilian genus Protosuchus.
(Galton, 1971)
The Lower Jurassic Navajo Sandstone of northern Arizona and southern Utah has yielded a diverse assemblage of late Early Jurassic terrestrial tetrapods from eolian and associated paleoenvironments. Although rare, vertebrate body fossils are represented by specimens of tritylodonts, crocodylomorphs, sauropodomorphs, and basal theropods (including Segisaurus halli).
(Irmis)


Prosauropod stuff: http://www.jstor.org/pss/4523036
"Galton (1976) recognized only two prosauropod genera (both monotypic) from North America, the anchisaurid Anchisaurus polyzelus and the plateosaurid Ammosaurus major. Anchisaurus is known by both skull and postcranial remains from the Newark Series of the eastern United States in Connecticut and Massachusetts. Ammosaurus has a wider distribution, having been found in the Portland Beds Connecticut and in the Navajo Sandstone of northern Arizona (Galton, 1976). As yet, no skull of Ammosaurus has been found in Arizona; in fact, the only known skull of this genus, associated with one of the Connecticut specimens, is too incomplete and crushed for detailed study."


The Prosauropod Dinosaur Ammosaurus, the Crocodile Protosuchus, and Their Bearing on the Age of the Navajo Sandstone of Northeastern Arizona
Author(s): Peter M. Galton
Source: Journal of Paleontology, Vol. 45, No. 5 (Sep., 1971), pp. 781-795
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1302773
Very few skeletons of prosauropod dinosaurs have been found in North America, and most of these are from the Upper Triassic of the Connecticut Valley (Lull, 1953). An exception is the specimen described by Brady (1935) from the Navajo Sandstone of north- eastern Arizona. Brady (1935) referred this specimen to Ammosaurus, a prosauropod genus hitherto known only from the Connecticut Valley. The Navajo Sandstone is an aeolian deposit (see Gregory, 1917, p. 59; Camp, 1936, p. 40; Baker et al. 1936, p. 52) that outcrops extensively in Utah, Arizona, Nevada, Colorado and New Mexico (see Heaton, 1950, fig. 9) and reaches a thickness of at least 2100 feet in southern Utah. Only one other reptile has been described from this formation, the coelurosaurian dinosaur Segisaurus (Camp, 1936), but Dr. C. L. Camp also collected two undescribed partial skeletons, one referable to Ammosaurus and the other to the crocodilian genus Protosuchus (see below).
There has been some confusion about whether Ammosaurus major from the Connecticut Valley is a primitive coelurosaur or a prosauropod, so a discussion of the relevant features of the Connecticut Valley specimens is necessary. The Navajo specimens are relevant to this problem and also to the age of the Navajo Sandstone. The Navajo is usually considered Early Jurassic, but Lewis et al. (1961) have suggested that at least part of it is Late Triassic.
There are two genera of prosauropods re- ported from North America for which postcranial material is available; these are Anchisaurus and Ammosaurus from the Upper Triassic rocks of the Connecticut Valley.

SPECIMENS FROM THE NAVAJO SANDSTONE Prosauropod dinosaurs
The stratigraphic occurrence was in typically cross-bedded Navajo Sandstone that Brady estimated to be about 80 to 100 feet below the top of the formation. Brady (1935, p. 213) noted that "the animal appears to have been buried entire in the position in which it died,… The up- per parts . . . seem to have been entirely re- moved by recent erosion." There are several incomplete caudal vertebrae, the centra of which are not as high as in Plateosaurus (Huene, 1926) and resemble those of Ammosaurus.
Baird (personal communication) has informed me that another specimen, a trackway, was undoubtedly made by a prosauropod dinosaur walking quadrupedally.

Identity of the Navajo prosauropod
The manus of the Berkeley specimen (Text- fig. 4) is clearly that of a prosauropod dinosaur (see below) and, on the basis of the similarity between the pedal ungual phalanges of the Berkeley and Flagstaff specimens (Text-figs. 3, 6A-D), it is reasonable to refer both to a single genus. The other prosauropod characters of the Navajo specimens are indicated in Table 1 and these characters are discussed more fully below for the Connecticut Valley specimens.
It is reasonable to refer the Navajo specimens to the genus Ammosaurus. The Navajo specimens may represent a new species; one difference from A. major is that the obturator foramen of the pubis (Text-fig. 1A) appears to be much smaller (Text-fig. 9).
Bearing in mind the incompleteness of the three specimens concerned and the questionable nature of the differences, I consider it inadvisable to erect a new species on the basis of the material available. The Navajo specimens are best regarded as Ammosaurus cf. major.



Clark, James M., David E. Fastovsky, Vertebrate Biostratigraphy of the Glen Canyon Group in northern Arizona. http://books.google.com/books?hl=en&lr=&id=1nZrbiUfMmMC&oi=fnd&pg=PA285&dq=Clark+and+Fastovsky,+1986&ots=FXFcPQHEQc&sig=dl4L46_8r6RibDICkHnurGLDT-c#v=onepage&q=&f=false
The first fossil discovered in the Navajo Sandstone was found in 1933 in Segi (or Tsegi) Canyon near Shonto, Arizona. The specimen, a partial skeleton of a small teropod dinosaur, was described by Camp (1936) as Segisaurus halli. Fragmentary “prosauropod” dinosaur specimens were collected in the same area in the 1930s… and a “prosauropod” dinosaur trackway was collected by the MNA in 1958 from near the head of the Segi Canyon. In 1968, a UCMP party found a fragmentary specimen of a small crocodilian in the same area. The only other fossils reported from the Navajo since then are trackways in Utah (Stokes 1978).
The type of specimen of the ichnotaxon Navahopus falicpollex Baird 1980 was found in the upper part of the Navajo Sandstone far to the west of these specimens… It has been identified as the trackway of a “prosauropod” dinosaur (Baird 1980).

The Fossil Trackway Pteraichnus: Not Pterosaurian, but Crocodilian
Author(s): Kevin Padian and Paul E. Olsen
Source: Journal of Paleontology, Vol. 58, No. 1 (Jan., 1984), pp. 178-184
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1304743

Stokes (1978) also assigned prints from the underlying Na- vajo Formation (Lower Jurassic) to Pteraich- nus, although they are much more poorly pre- served than those from the Morrison. These cannot be regarded as the earliest evidence of pterosaurs (Stokes, 1978; Anonymous, 1973), which in any case are known from the Norian (Upper Triassic) of Italy (Zambelli, 1973); but if they are indeed like Pteraichnus, then the crocodile Protosuchus, which has been recorded by Camp from the Navajo Sandstone (Galton, 1971), could be consid- ered as a possible trackmaker

Vertebrate ichnological diversity and census studies,
Lower Jurassic Navajo Sandstone
Emma C. Rainforth
1997
Research Report submitted in partial fulfillment of the degree of
Master of Science.
Department of Geological Sciences,
University of Colorado at Boulder.
http://www.ldeo.columbia.edu/~emmar/research/rainforth1997.pdf
Only a small body fauna is known from the Navajo Sandstone, and includes a crocodylomorph, a few partial tritylodonts and prosauropods, and a small theropod. In contrast, 18 ichnogenera have been discovered, representing up to 9 vertebrate families. Whilst the animals known from skeletal remains are represented by tracks, the ichnites suggest that large theropods, lizards, thyreophorans, and possibly basal ornithischians and pterosaurs also inhabited this environment. Clearly where tracks are present they can increase our knowledge of the vertebrate component of the ecosystem in strata with a poor body fossil record.
Tracks provide information on the environments frequented by particular animals because they are in situ biogenic sedimentary structures; however this also means that substrate conditions can play an important role in determining track morphology and preservation. In the Navajo Sandstone only the smallest tracks are found on dune foresets, and the whole range of track sizes (except for the smallest) are preserved in interdune environments. This size sorting is due to differences in substrate texture and composition rather than being behaviorally or paleoecologically determined. However the predominance of carnivore tracks around wet interdune deposits (oases) is probably a result of behavioral and sedimentological variations on a daily basis.
Tracksites
Vertebrate tracks occur in several facies of the Navajo Sandstone; these can be classified as dune or interdune environments. Tracks in the dune environments occur on the foresets; generally the trackways are trending up-slope. The interdune environment can be further subdivided into truncation (or bounding) surfaces between dune sets; and horizontally-bedded interdunal deposits. Tracks in these environment are usually, perhaps always, undertracks. These latter have a range of lithologies even within a single vertical interdune sequence, varying from siliciclastic to calcareous sand to limestone, which in some instances can be demonstrated to have algal laminations. Pseudomorphs after evaporitic structures occur in some of the limestones. The limestone interdunal sequences would have formed in ephemeral playa lakes.
Many of the tracks are preserved with sufficient morphological detail as to merit assignation of an ichnotaxonomic name at the generic level. In general ichnospecies cann ot be assigned because (a) the tracks are not well-enough preserved, and (b) the taxonomy of Late Triassic and Early Jurassic vertebrate tracks is in a confused state at the present time, with an excess of names that in many cases are junior synonyms of other ichnotaxa. With such constraints, I do not think it particu-larly valuable to attempt to assign ichnospecific names. Exceptions are Navahopus falcipollex, an ichnogenus and ichnospecies known only from a single trackway in the Navajo of northern Arizona (Baird, 1980; Figure 2); Trisauropodiscus moabensis, an ichnospecies known only from the Navajo near Moab, Utah (Lockley and Hunt, 1995; Figure 3); and Otozoum, which has two easily disting-uishable ichnospecies (O. moodii, O. minus; Figure 4), both of which are known from the Navajo. Unfortunately there are tracks which it is not possible to identify, owing to their poor preservation. Such tracks can occur in any of the facies within the Navajo, and are of limited usefulness.
Below is a list of the ichnotaxa known from the Navajo:
Grallator
Eubrontes
Anchisauripus
(It is possible that Grallator, Anchisauripus and Eubrontes are artificial divisions of a continuous ontogenetic growth series (Olsen, 1980). However, that assumes that there were no small trackmakers of this type. In addition, the relative lengths and positions of the digits varies between these ichnotaxa; however, modern ratites’ feet grow at different rates, resulting in slightly different morphologies with age (Farlow, personal communication, 1996). This track is uncommon relative to Grallator and Eubrontes.)
Anomoepus
Trisauropodiscus moabensis
Dilophosauripus
Otozoum
Navahopus
Tetradactyl morph A
Brasilichnium

References (not complete or formatted)
Galton, Peter M., 1971, The Prosauropod Dinosaur Ammosaurus, the Crocodile Protosuchus, and Their Bearing on the Age of the Navajo Sandstone of Northeastern Arizona, Journal of Paleontology, Vol. 45, No. 5, pp. 781-795.
Faul, Henry, Wayne Roberts, 1951, New Fossil Footprints from the Navajo Sandstone of Colorado, U.S. Geological Survey.
Irmis, Randall B., A Review of the Vertebrate Fauna of the Lower Jurassic Navajo Sandstone in Arizona, Department of Integrative Biology and Museum of Paleontology.




Notes from Fastovsky on Revision:

- Ammosaurus is a body fossil. Name the trace fossil that can also be used to date the N.S. What is the age of this organism? Where else have these fossils been found (connecticut?). What is the radiometric age determined for that organism in that formation?
- Decide on one range of age for the stages, and cite it correctly. Or, do not even talk about numerical ages of stages.
- Don't talk about source of sediments at all. Other irrelavent things: facts about the fossils when they were alive, colors of the sandstone, radiometric dating (aside from dating the body fossils).

Things to think about:
- He said it was an aeolian system, at one time a functioning desert.
- Connecticut formation and the dates found there for the biostratigraphy
- Lithostratigraphy: stages above and below the N.S. How were those ages determined?
- Cite accurately



Synthesis Paper #2 - Revision suggestions:

GSA Formatting:
- If citing a source in a paragraph, it should include the date: (Kocurek, 2003).
- For changes to formatting on References Cited page, please look at our Notes and Resources page.

Major Content Changes:
- Condense these sections: Sediment Source and Radiometric Dating.
Maybe change Sediment Source to "About the Navajo Sandstone", but keep this section short and brief, because this is just a side note and not at all required for answering our problem. Some of the information in this section may even be able to be mentioned in passing in the intro, but the intro is already good (just remove what was crossed out of course).

- We really need to expand the Biostratigraphy section, this is where we'll probably get the most back if we edit it right. The professor also mentioed Lithostratigraphy.
  • Biostratigraphy: The identification of fossils found within sedimentary rock strata as a method of determining the relative geologic age of the rock.
  • Lithostratigraphy: The examination and dating of surrounding sediment layers to determine the date of a stratigraphic layer located in the middle.


(more coming soon)


ABSTRACT
An eolian formation known as the Navajo Sandstone is located in the southwestern area on the North American continent. The deposition of this sandstone is shown to have been occurred during the Jurassic period, more specifically from 178 to 192 million years ago. This time is also known as the Toarcian turnover. To accurately determine the age of this sandstone layer, methods such as biostratigraphy, the examining of existing index fossils to yield a relative date range, and the science of lithostratigraphy to discover the ages of surrounding sandstone and materials were used.

INTRODUCTION
Spreading across northern Arizona, northwest Colorado, Nevada, and Utah, the Navajo Sandstone is located in what is called the Colorado Plateau. This formation of sediment consists of sandstone that through time has come to display an array of colors and is dated to be from the Early Jurassic period. There are several different means to determine the age of a stratigraphic layer. In regards to the Navajo Sandstone, biostratigraphy, lithostratigraphy, and radiometric dating are just a few key ways of determining the age of this layer.

Biostratigraphy
Biostratigraphy of the Navajo Sandstone is best done using one or more index fossils. (expand on this! we need to find one of these fossils and explain how the fossil was dated, then explain why this date helps to pin-point the date of the Navajo Sandstone)

Radiometric Dating
The method of radiometric dating is commonly used to find the ages of igneous or metamorphic rocks (Kocurek, 2003), however there were a few useful calculations through the use of this method for dating the Navajo Sandstone. (more content to come from paper, should be condensed first. Also, Rahl and Reiners needs to be cited correctly)

A second method used here was helium dating, which is a method of dating that is dependent on the production of helium isotopes of uranium and thorium. The retaining of helium within any rock capable of this retention will increase during the lifetime of such a rock, and as a result, the ratio of helium to its radioactive ancestors (such as...) then becomes a means to measure the geologic date.

Lithostratigraphy
Below the Navajo Sandstone lies the formation known as (insert info here). This layer was dating using the following methods: (insert info here) and was concluded to be (insert info here) years old. (I'm pretty sure the surrounding layers are also from the Jurassic period, so just saying "Jurassic" might not be enough here)


CONCLUSION
With the ages of surrounding sediment layers, the ages of fossils found within the Navajo Sandstone, and radiometric dates, this sandstone layer was deposited between (insert date info here).

*THIS LOOKS LIKE EXACTLY WHAT WE NEED AND BEING FROM URI WE'RE ALLOWED ACCESS BUT I DON'T KNOW HOW TO DO IT WHILE NOT IN THE LIBRARY BUT IT SAYS THERE IS A WAY*
Paleontology Journal on Ammosaurus of Conn.



















Dating the Navajo Sandstone

Amy Lombari__
Zoe Gentes
Dennis Titterton
Andrew Infante
Jennifer Sullivan
12 October 2009

ABSTRACT
The Navajo Sandstone is a geologic formation in the southwestern part of the Northern American continent, the age of which can be found using different techniques. One method is to look at the paleoenvironment and determine the source of deposition. Studies show that this formation was deposited in an Aeolian environment. The direction of ripples and the radiometric ages of zircons in the sediment point towards the source of deposition being the Appalachian Mountains and not the Rocky Mountains. This is our first guideline for geologic age: the Navajo Sandstone is older than the Rocky Mountains, formed 170 million years ago. Another way to determine the age is to use biostratigraphy to study the particular fossils in this sandstone, such as the tracks of the Ammosaurus. This organism lived in the Jurassic Period, 199.6-145.5 million years ago, which provides us a more specific guideline as to when this sandstone was formed. Using the results found by these dating techniques, we conclude that the Navajo Sandstone is of the Pliensbachian-Toarcian Stages during the Jurassic Period, dating between 178 and 192 million years old. This would place the formation of this sandstone during the Early Jurassic extinction, alternately called the Toarcian turnover.

INTRODUCTION
The Navajo Sandstone is an expansive geologic formation spreading across northern Arizona, northwest Colorado, Nevada, and Utah, located in the Colorado Plateau province of the United States. The formation consists of early Jurassic sedimentary rocks and is famous for its beautiful color variations. These colors, including crimson, orange, peach, pink, gold, yellow, and white, are caused by chemical reactions with varying isotopes of iron oxide that precipitated into the strata.
While the Navajo Sandstone is an incredibly beautiful formation to look at, the study of its history is as complex as the colors it is composed of. How did the Navajo Sandstone form? How old is it? What geologic stage did it originate from? With a few different scientific methods, we can answer these questions. First, we will determine the paleoenvironment and see if there is useful information regarding the source of sediment deposition. Next we can look at radiometric dating and determine if good numerical dates can be taken from this method. Lastly, we will use biostratigraphy to relatively date the formation with fossils found within. With all of the results, we should be able to determine the geologic stage of the Navajo Sandstone.


SEDIMENT SOURCE
The Navajo Sandstone has cross-beds up to 30 meters high and current ripple marks like those produced by wind today, determining these are windblown deposits. Studies show that the sandstone is mostly well-sorted, well-rounded quartz with grain sizes measuring 0.2 to 0.5mm in diameter, typical of Aeolian deposits (Chan). Due to the fact that the cross-beds dip generally southwest, we realize that the wind blew mostly from the northeast, which would indicate that the source of deposition was not the relatively young Rocky Mountains, which started to form 170 million years ago, as was previously thought. Instead, a more likely source for the sediments composing the Navajo Sandstone would be the Appalachian Mountains, which began forming about 480 million years ago. The first estimate of geologic age that we arrive at is that the Navajo Sandstone is not as young as was once thought, and is actually older than the Rockies. This inferred range of dates is far too broad for our purpose of narrowing the age down to a stage. Despite this, we can use numerical ages from radiometric dating to narrow it further.

RADIOMETRIC DATING
Radiometric dating is most commonly used to find the ages of rocks in the igneous or metamorphic categories (Kocurek). But there have been some useful calculations to come out of this method of dating for the sedimentary Navajo Sandstone. Jeffrey Rahl and Peter Reiners, geologists from Yale University, used two forms of radiometric dating to determine when zircon grains found in the Navajo Sandstone formed and cooled. One form they utilized was uranium-lead dating. This is a technique used to date materials based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. Therefore, by using this technique, researchers found that most of the grains were formed between 1.2 billion and 950 million years ago.
The second method they used was helium dating, a method of dating that depends on the production of helium during the decay of radioactive isotopes of uranium and thorium. Because of this decay, the helium content of any rock capable of retaining helium will increase during the lifetime of that rock, and the ratio of helium to its radioactive ancestors then becomes a measure of geologic time. By using helium dating, they found that the grains cooled and therefore eroded between 500 million and 250 million years ago
(Pratt).
There is only one place in North America with zircons such as these, and that is the Appalachian Mountains. This confirms what the windblown ripples in the sandstone have told us about the source of the deposition. Furthermore, the dates determined by the methods used by Rahl and Reiners provide a better guideline for the age of the Navajo Sandstone than simply that it is older than the Rocky Mountains. These ages of the cooling and erosion of the grains suggest that the sandstone formed hundreds of millions of years after the birth of the Appalachians, the source of the sediments. But we can narrow down the age even further, using the fossils contained within the formation.


BIOSTRATIGRAPHY
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. There are many fossilized remains in the Navajo Sandstone, mostly trace fossils, because the erosive nature of the sandstone destroyed most of the body fossils.
Stromatolites were discovered in the sediments of the Navajo Sandstone. Stromatolites are the oldest macroscopic evidence of life on Earth, at least 2.5 billion years old, and still form today in some oceanic settings, primarily tidal zones where water is introduced in an elongated pulsing fashion. During the 1.5 billion years of Earth history, before marine invertebrates appeared, stromatolites were the most obvious evidence of life, and they occur sporadically throughout the remainder of the geologic record
(Rainforth). The presence of these stromolites provides geologists with information that determines that the Navajo Sandstone was once a semi-aquatic environment. Also, tracks from the ancestral crocodile Protosuchus were found in the Navajo Sandstone. Although this reptile lived not in the water, but on land, its habitat consisted of riverbeds in North America, proving more evidence of the semi-aquatic environment.
The trace fossils of tracks left by a prosauropod called the Ammosaurus lead scientists to believe the formation dates fall into the Jurassic Period, ranging 199.6-145.5 million years ago. The Ammosaurus, or sand lizard, averaged a length of 13 feet, which is small for their suborder, but left them to be one of the most versatile dinosaurs of their time. It existed during the Early and Middle Jurassic Period of North America, more specifically during the Pliensbachian Stage (189.6-183 million years ago) through the Toarcian Stage (183-175.6 million years ago).


CONCLUSION
With an approximate age, a good idea of the sediment source, and significant fossil evidence, we can come to the conclusion that the Navajo Sandstone is an Aeolian sand dune, due to the winds ability to shape the sand. It was also determined that the Navajo Sandstone is mainly composed of sediments from the distant Appalachians. Uranium-lead radioisotope dating and helium dating of the Navajo Sandstone concluded that the zircon grains within the rock could only have derived from one region in North America: the Appalachian Mountains. Through biostratigraphy, we determined that the Navajo Sandstone contains fossils that are indicative of the Jurassic Period, most specifically the Pliensbachian and the Toarcian Stages. Thus, we concluded that the Navajo Sandstone formed between 192 and 178 million years ago, towards the end of the Pliensbachian Stage and the beginning of the Toarcian Stage.

References Cited
Chan, M.A., and A.W. Archer, 2000, Cyclic Aeolian Stratification on the Jurassic Navajo Sandstone, Zion National Park: Periodicities and Implications for Paleoclimate, D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, eds., Geology of Utah's Parks and Monuments. Utah Geological Association Publication 28:1-11.

Kocurek G. 2003. Limits on extreme Aeolian systems: Sahara of Mauritania and Jurassic Navajo Sandstone examples, M. Chan and A. Archer, eds., Extreme Depositional Environments: Mega End Members in Geologic Time.

Pratt, Sara, November 2003, “Tracing the Navajo Sandstone,” Geotimes.

Rainforth, E.C., 1997, Vertebrate Ichnological Diversity and Census Studies, Lower Jurassic Navajo Sandstone PDF ver... Unpublished masters thesis, Department of Geological Sciences, University of Colorado, Boulder.