Taphonomy and Rare Earth Taphonomy and Rare Earth Element Geochemistry of the Element Geochemistry of the

Stegosaurus sp.Stegosaurus sp. at the at the Cleveland Lloyd Dinosaur Cleveland Lloyd Dinosaur

Quarry, Emery County, UtahQuarry, Emery County, Utah

by Celina Suarezby Celina Suarez

Trinity UniversityTrinity University Temple Temple UniversityUniversitySan Antonio, TXSan Antonio, TX Philadelphia, PAPhiladelphia, PA

Geologic SettingGeologic Setting

Morrison FormationMorrison Formation Brushy Basin MemberBrushy Basin Member

Exposed by the San Exposed by the San Rafael monoclineRafael monocline

Located below Located below variegated beds of the variegated beds of the upper most Brushy upper most Brushy Basin, in a section Basin, in a section dominated by gray dominated by gray siltstones, lacustrine siltstones, lacustrine limestones, and small limestones, and small channel sandstones.channel sandstones.

The Cleveland Lloyd Dinosaur The Cleveland Lloyd Dinosaur QuarryQuarry

The largest deposit of The largest deposit of Allosaurus fragilisAllosaurus fragilis in the world in the world – 47 (Gates, 2002)– 47 (Gates, 2002)

over 10,000 bonesover 10,000 bones Deposited in a calcareous Deposited in a calcareous

mudstone with small mudstone with small concretions to large concretions to large concretionary layers of concretionary layers of carbonate, capped by a carbonate, capped by a lacustrine limestonelacustrine limestone

Most recent research: Most recent research: ephemeral pond that ephemeral pond that accumulated bones as the accumulated bones as the result of multiple drought result of multiple drought events (Gates, 2002)events (Gates, 2002)

Taphonomy and Rare Earth Element Taphonomy and Rare Earth Element Geochemistry the Geochemistry the Stegosaurus spStegosaurus sp. in the . in the

CLDQCLDQ

Is the taphonomic analysis of the Stegosaurs in the research square significantly different than the taphonomic analysis of the Allosaurs?

Is the REE geochemistry of the Stegosaurs significantly different from the Allosaurs?

Does the REE geochemistry analysis support the findings of Gates (2002)?

Population StudyPopulation Study

Various taphonomic approaches to Cleveland Lloyd… Bone positioningBone positioning Taphonomic markings or Taphonomic markings or bone alteration and surface features Lithologic EvidenceLithologic Evidence Rare Earth Element GeochemistryRare Earth Element Geochemistry

Review collections material => population Review collections material => population number of number of StegosaurusStegosaurus

Excavation and Mapping => biostratigraphic Excavation and Mapping => biostratigraphic positions and orientation of bonespositions and orientation of bones

Taphonomic Analysis => abrasion, weathering, Taphonomic Analysis => abrasion, weathering, fracture, surface tracesfracture, surface traces

Rare Earth Element Geochemistry => Rare Earth Element Geochemistry => concentrations and ratiosconcentrations and ratios

Results: Population SurveyResults: Population Survey Minimum of six Minimum of six

individuals of individuals of StegosaurusStegosaurus based based on the number of on the number of humeri and humeri and scapulaescapulae

Element Type Length UMNHVP#UUVP# Comments

Appendicular

HUMERUS R ? 3039 ?HUMERUS R 40-656 ?HUMERUS R 40-657 ?Humerus R 5694 CEUMHumerus R 450 5271 5696 noneHumerus R ? 3474 LACMHumerus L 450 3809 LACM; CEUM?

Femur R 760 5272 5699Femur R 770 5274Femur R 2376 LACMFEMUR R 40-651 ?FEMUR R 40-652 ?Femur L 890 5275 5693Femur L 5278 broken, condial only?FEMUR L ? 2375 ?FEMUR L 4354 ?

Scapula/coracoidR 5691 CEUMScapula/coracoidR 680 5546a 5690aScapula R 580 5483 5689SCAPULA R 40-653 ?Scapula/coracoidR 570 721 broken distally?Scapula/coracoidL 870 5276 2561Scapula L ? 3423 LACMSCAPULA L 3017 ?Scapula/coracoidL 590 5692SCAPULA L 40-654 ?Scapula L 660 5277 3017SCAPULA ? ? 2529 ?

Mapping and ExcavationMapping and Excavation

StegosaurusAllosaurusOther

Stegosaurus

Allosaurus

Allosaur

Stegosaur

Sauropod and Stegosaur

Bone PositioningBone Positioning Mostly flat lyingMostly flat lying Some degree of Some degree of

orientation due to orientation due to seasonal fluvial activityseasonal fluvial activity

Bones in the research Bones in the research square are square are autochthonous based autochthonous based on the presence of on the presence of large bone material large bone material and small sediment and small sediment size, which is also size, which is also consistent with findings consistent with findings by Gates (2002).by Gates (2002).

Taphonomic MarkingsTaphonomic Markings Pathologic Deformation-left sidePathologic Deformation-left side

Taphonomic Markings: FractureTaphonomic Markings: Fracture

Only one: Only one: Allosaurus Allosaurus gastraliagastralia

30% of bones 30% of bones in the bones in the bones surveyed by surveyed by Gates (2002) Gates (2002) have have fracturesfractures

No significant No significant tramplingtrampling

Taphonomic Analysis: Surface Taphonomic Analysis: Surface TracesTraces Teeth Marks – only Teeth Marks – only StegosaurusStegosaurus, none on , none on AllosaurusAllosaurus bones bones

Throughout the quarry, bones of herbivorous dinosaurs contain the most teeth marks (Gates, 2002).Throughout the quarry, bones of herbivorous dinosaurs contain the most teeth marks (Gates, 2002). Allosaurs preferentially prey upon the herbivorous animals, rather than scavengeAllosaurs preferentially prey upon the herbivorous animals, rather than scavenge

AbrasionAbrasion Abrasion – mostly low, and slightly more on Abrasion – mostly low, and slightly more on StegosaurusStegosaurus

bonesbones Gates (2002), notes prevalence of low level of abrasion on Gates (2002), notes prevalence of low level of abrasion on

centra of vertebraecentra of vertebrae Bias since majority of Bias since majority of StegosaurusStegosaurus material were vertebrae material were vertebrae Supports some fluvial activity when combined with bone Supports some fluvial activity when combined with bone

orientation dataorientation data

Taphonomic MarkingsTaphonomic Markings

At least portions of the bones in the quarry At least portions of the bones in the quarry were exposed because of evidence of were exposed because of evidence of scavenging/ predation.scavenging/ predation. Weathering stages between 0 and 1 – not Weathering stages between 0 and 1 – not

significant exposuresignificant exposure Stegosaurs were more susceptible to Stegosaurs were more susceptible to

predation due to drought conditions (Gates, predation due to drought conditions (Gates, 2002). 2002). Bias of teeth marks on the Bias of teeth marks on the StegosaurusStegosaurus bones bones

versus the versus the AllosaurusAllosaurus bones bones AllosaurusAllosaurus preferred predation rather than preferred predation rather than

scavenging since there are less teeth marks on scavenging since there are less teeth marks on AllosaurusAllosaurus bones bones

Results: Lithology – Thin SectionsResults: Lithology – Thin Sections Mostly clays, CaCOMostly clays, CaCO33, ,

plagioclase, quartz, plagioclase, quartz, some hematitesome hematite

Microfossils – Microfossils – ostracodes and ostracodes and charophytescharophytes

Microfossils – Microfossils – indicative of shallow, indicative of shallow, low-energy waterlow-energy water

1 mm 1mm

1mm

Rare Earth Element Rare Earth Element GeochemistryGeochemistry

La – LuLa – Lu During weathering, During weathering,

REE undergo REE undergo fractionationfractionation

Aqueous REE Aqueous REE signatures vary with signatures vary with pH and redox pH and redox conditions in conditions in different different depositional depositional environmentsenvironments

Fractionation and REE of Fossil BoneFractionation and REE of Fossil Bone

REE substitute for Ca REE substitute for Ca in the biogenic in the biogenic apatite crystal apatite crystal structure during early structure during early diagenesis diagenesis

Bones record the Bones record the pore-water REE pore-water REE chemistry of the chemistry of the original original depositional/diagenetdepositional/diagenetic environmentic environment

REE SignaturesREE Signatures

HREE are associated with alkaline waters HREE are associated with alkaline waters (high pH)(high pH)

LREE are associated with acidic and LREE are associated with acidic and neutral waters (low pH)neutral waters (low pH)

Alkaline environments include: evaporitic Alkaline environments include: evaporitic lacustrine settings – established lakes with lacustrine settings – established lakes with high degree of evaporation, carbonate high degree of evaporation, carbonate depositiondeposition

Acid environments include: water-logged Acid environments include: water-logged settings such as swampy areassettings such as swampy areas

REE Geochemistry Bone Sampling

• Cortical bone was collected from Allosaurus and Stegosaurus bones excavated from the research square

• Cortical bone has a higher concentration of REE than trabecular bone

Comparing the Comparing the AllosaurusAllosaurus and and StegosaurusStegosaurus bones: bones:

All bones have similar signatures (shape)

All bones are fossilized in same environment

Eu anomaly indicates volcaniclastic REE source

Signatures of bones in the quarry are flat with a slight depletion of HREE indicating a neutral pH to slightly acidic environment

Ternary Ternary DiagramDiagram

The ternary diagram is a way to quantify spider diagram in a more presentable format

Ternary shows relative ratios of Light REE – Nd Middle REE – Gd Heavy REE – Yb

Points are clustered showing similar REE ratios i.e. the same depositional environment

Supports an autochthonous deposit of bones – also seen in taphonomic evidence

REE concentrations of total data set:Includes bones from quarry: mudstone, contact, and capping limestone; plus limestone ridge to the north

Neutral pH environment

Fluvial activity * orientation * abrasion * rip-up clasts (Gates, 2002)

Indicate:

REE Geochemistry: Depositional REE Geochemistry: Depositional SettingSetting

Supports the “ephemeral” pond Supports the “ephemeral” pond setting described by Gates (2002).setting described by Gates (2002). Occasionally to seasonally dries outOccasionally to seasonally dries out Flooding/ or wet season refreshed the Flooding/ or wet season refreshed the

pond with neutral pH giving flat REE pond with neutral pH giving flat REE signatures, and orienting the bonessignatures, and orienting the bones

Neutral pH pond area, not established lakeNeutral pH pond area, not established lake

ConclusionsConclusions

Six Stegosaurs are currently found at the CLDQ. One Stegosaur is Six Stegosaurs are currently found at the CLDQ. One Stegosaur is represented in the study area.represented in the study area.

All the bones in the quarry were fossilized in the same All the bones in the quarry were fossilized in the same depositional environment, supporting an autochthonous depositional environment, supporting an autochthonous accumulation. accumulation.

The depositional environment of Cleveland Lloyd was a neutral pH The depositional environment of Cleveland Lloyd was a neutral pH environmentenvironment Ephemeral pondEphemeral pond Some fluvial action due to oriented and slight abrasion of Some fluvial action due to oriented and slight abrasion of

bones and enough sediment supply to depress the formation of bones and enough sediment supply to depress the formation of only limestone, and give flat REE signaturesonly limestone, and give flat REE signatures

Not enough water to support aquatic fauna or significant plantsNot enough water to support aquatic fauna or significant plants Microfossils support shallow water environmentMicrofossils support shallow water environment

These occasional to seasonal variations supported by These occasional to seasonal variations supported by paleoenvironmental interpretations of the Morrison Formation as paleoenvironmental interpretations of the Morrison Formation as being highly seasonal by Dodson being highly seasonal by Dodson et al.et al. (1980) (1980)

AcknowledgementsAcknowledgements Temple UniversityTemple University: Dr. David E. Grandstaff and Dr. Dennis O. : Dr. David E. Grandstaff and Dr. Dennis O.

Terry Jr.Terry Jr. Trinity UniversityTrinity University: Dr. Edward C. Roy Jr.: Dr. Edward C. Roy Jr. Univ. of UtahUniv. of Utah: Dr. Scott Sampson, Bucky Gates, Lindsay Zanno: Dr. Scott Sampson, Bucky Gates, Lindsay Zanno Utah Museum of Natural HistoryUtah Museum of Natural History: Mike Getty, Monica Castro, : Mike Getty, Monica Castro,

Joe Gentry, Jerry GoldenJoe Gentry, Jerry Golden BLM – Price Field OfficeBLM – Price Field Office: Mike Leschin, Frank Davis, Sam : Mike Leschin, Frank Davis, Sam

Espinoza, Elsa LangraneEspinoza, Elsa Langrane Univ. of PennsylvaniaUniv. of Pennsylvania: Dr. Peter Dodson and his Evolution of : Dr. Peter Dodson and his Evolution of

Dinosaurs classDinosaurs class Doreena PatrickDoreena Patrick Dr. Clive TruemanDr. Clive Trueman Financial SupportFinancial Support: Trinity University, Tinker Family, GSA : Trinity University, Tinker Family, GSA

South-Central Undergraduate Research Grant Program, Bureau South-Central Undergraduate Research Grant Program, Bureau of Land Management of Land Management

Marina Suarez, and all friends, family, and reviewersMarina Suarez, and all friends, family, and reviewers

ReferencesReferences

Dodson, P., Behrensmeyer, A.K., Bakker, R.T., and McIntosh, J.S., 1980, Dodson, P., Behrensmeyer, A.K., Bakker, R.T., and McIntosh, J.S., 1980, TaphonomyTaphonomy

and Paleoecology of the dinosaur beds of the Jurassic Morrison and Paleoecology of the dinosaur beds of the Jurassic Morrison Formation:Formation:

Paleobiology, v. 6, no. 2, p. 208 – 232. Paleobiology, v. 6, no. 2, p. 208 – 232.

Gates, T.A., 2002, The Cleveland Lloyd Dinosaur Quarry as a Gates, T.A., 2002, The Cleveland Lloyd Dinosaur Quarry as a drought-induced assemblage: late Jurassic Morrison Formation, drought-induced assemblage: late Jurassic Morrison Formation, central Utah [Master of Science Thesis]: Salt Lake City, Utah central Utah [Master of Science Thesis]: Salt Lake City, Utah

University of University of Utah, 57p.Utah, 57p.

Trueman, C.N., 1999, Rare earth element geochemistry and taphonomy of Trueman, C.N., 1999, Rare earth element geochemistry and taphonomy of vertebrate vertebrate assemblages: Palaios, v. 14, p. 555-558.assemblages: Palaios, v. 14, p. 555-558.

Trueman, C.N. and Tuross, N., 2002, Trace elements in recent and fossil Trueman, C.N. and Tuross, N., 2002, Trace elements in recent and fossil bone bone apatite, apatite, in in Kohn, M.J., Rakovan, J.F., Hughes J.M., eds., Reviews in Kohn, M.J., Rakovan, J.F., Hughes J.M., eds., Reviews in

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