sediment - Universität Tübingen

The)Pleistocene)megafauna)of)Argentina:)
13
Impact)of)diagenesis)on)stable)isotopes)(δ C,)
18
δ O))in)xenarthran)fossil)teeth
Stefan-7esemerkK-íartin-0ottekK-~ervé-7ocherenskKP
k
-Wepartment-of-qeosciencesK-7iogeologyK-Xberhard-+arls-Universität-TübingenK- P-Senckenberg-0enter-for-~uman-Xvolution-and-†alaeoenvironment-é~X†DK-Xberhard-+arls-Universität-Tübingen--
Overview
Methods
The-longUterm-isolation-of-South-ßmerica-produced-a-highly-peculiar-endemic-faunaKxenarthrans- being- a- prime- exampleä- These- animals- were- quite- successful- andKaccording-to-their-fossil-recordK-even-populating-the-‰orth-ßmerican-continentä-Thequestion- arises- why- some- of- the- most- peculiar- xenarthran- familiesK- like- the- giantground-slothsK-went-extinct-about-küäüüü-years-agoäk8
kA
%nsights-from-carbonate-isotopic-analysis-éδ 0K-δ VD-are-hindered-by-the-fact-thatxenarthrans- lack- enamel- on- their- teethK- which- is- the- material- proven- to- retainbiogenic-valuesä
We- therefore- test- the- hypothesis- that- NdurodentinNK- their- functional- analog- toenamelK-is-an-alternative-for-carbonate-analysisä
dentin
durodentin
sediment
Megatherium
Superorder
Vrder
Suborder
Scelidotherium
zamily
zolivora-éslothsD
†-íegatheriidae
éground-slothsD
Vermilingua
éanteatersD
7radypodidae
éthree-toed-slothsD
† Scelidotherium
0ingulata
Scelidotherium-molaréside-and-top-viewD
Sampling-of-NdurodentinNKdentin-and-sediment-éifavailableD-of-xenarthran-teeth
k3-individuals-have-been-sampled-éI-MegatheriumK6-ScelidotheriumK-8-Glyptodon-and-k-LestodonD
CarbonateDpretreatment
------‰aV0l-removes-organic-matter------------acetate-buffer-solution-removes-nonUlatticeUbound-carbonates
-----
† Lestodon
† Megatherium
† qlyptodontidae
† Glyptodon
IsotopeDratioDmassDspectrometryD(GasbenchDII)
Wasypodidae
éarmadillosD
qas-%RíSK-qeochemistry-"abK%sotope-qeochemistryK-Tübingen
Glyptodon
13 O
� 13C =
13 O
Diagenesis
18 O
---Xnamel-is-highly-crystalline-and-chemically-stable
Xnamel
Vranic-fraction.-~kB
---Wentin-is-more-susceptible-to-alteration
íineral-fraction.-~-FFBcalcium-phosphate-0a é†V D V~.----Diagenesis-and-fossilization-lead-to.includes-8B-carbonate-0V
---loss-of-organic-matter
WentinDDDincorporation-of-exogenous-material
Vranic-fraction.-~PPB
íineral-fraction.-~IAB---isotopic-exchange-with-sedimentary-fluids
calcium-phosphate.---includes-~6B-carbonate-0V
---------biogenic-signal-is-potentially-erased
--/ 8
PU-8
8
PU-
Durodentin is no surrogate for enamel
hypotheticalDdiageneticDpathway
������
12 O
Wiet
~abitat
− 1 ∙ 1000[‰]
����
16 O
������
16 O
�����
k3
k8
durodentin-site-ß
dentin-site-ß
sediment-site-ß
durodentin-site-7
dentin-site-7
8P
enamel
dentinTdurodentin
sediment
diagenetic-pathway
biogenic-variation
0ervid enamel
8ü
hypothetical-biogenetic
values
hypothetical-biogenetic
values
Toxodon enamel
0amelid-enamel
PA
P6
íesotherium enamel
Scelidotherium
backtrackingDoriginalDvalues
P3
"estodon
íegatherium
Pk
Ukk
Ukü
UF
UA
UI
U3
U6
U/
δk80-é‰-V†W7D
fossil site
Guideline
U8
species-P
species-k
biogenic-values
éduroUDdentin
sediment
species-8
δkAV-é‰-VSíVWD
P/
colderTmore-humid
I-íegatherium-------6-Scelidotherium-----k-"estodon-------8-qlyptodon
P8
UkP
kP
0omparing- values- of- Xenarthrans- to- taxa- that- do- bear- enamel- shows- thatseparation-is-observable-only-in-the-enamel-not-the-dentin-of-reference-speciesä
Xenarthrans- values- seem- to- be- homogenizedä- 7iogenic- values- are- altered- by- asedimentary-signal-in-all-dental-tissues-but-enamelä-
PI
Uk8
/-
~igh- precision- measurements- of- oxygen- é VT VD- and- carbon- é 0T 0D- isotopicratios-on-0VP-released-by-addition-of-phosphoric-acid-into-carbonate-sample
%sotopic-tracers-separate-species-from-one-another-and-allow-interpretation-aboutdietK-habitat-and-position-in-the-ecosystem
qlyptodon
δk80-é‰-V†W7D
08----------0
ßridityTemperature
− 1 ∙1000[‰]
kA
δkAV-é‰-VSíVWD
species-8
Wurodentin-vsä-dentin
PF
δkAV-é‰-VSíVWD
species-P
δkAV-é‰-VSíVWD
species-k
enamel
dentin
sediment
18 O
12 O
Comparison to enamel bearing taxa
%n-cases-where-enamel-is-preserved-and-values-are-diagenetically-alterated-we-canexpect--a-hypothetical-pathway-as-shown-in-the-graph-on-the-leftä‰o-general-trend-observable-for-the-alteration-of-durodentin-compared-to-dentinKwe-thus-expect-values-to-be-similarly-alteredäßn- exemplary- case- of- alteration- can- be- observed- for- the- outlier- values- of- aMegatheriumK- where- original- values- were- overprinted- by- a- marine- sedimentarysignal-émore-positive-δk80D8k
� 18O =
warmerTmore-arid
6
Megatherium-molar-
basic-steps-of-protocol.
kD-Vxidation-step------------------PD-"owUp~-step
Genus
†-íylodontidae
éground-slothsD
†ilosa
Xenarthra
íammalia
Xndemic-to-South-ßmerica
Xxtant-today.-slothsK-armadillosKanteaters
Xxtinct-since-~kü-ka.
†lacentalia
Xenarthrans
íarsupialia
0omparison- to- enamel- bearing- taxa- shows- that- isotopic- values- measured- inxenarthran-dental-tissue-are-biased-by-a-sedimentary-signalä
7y-reconstructing-the-diagenetic-pathway-a-qualitative-interpretation-can-be-made.Megatherium- has- the- most- selective- 0/- dietK- while- Scelidotherium- might- haveincorporated-08ä-Lestodon-and-Glyptodon-are-in-an-intermediate-positionä-ß-guideline-is-presented-for-evaluating-site-specific-requirements
6-cm
6-cm
Sampling
Conclusions
-
Lestodon
zossilxenarthranßrgentina
teeth-fromsites-of-BuenosD
Aires-regionKßrgentina-éToscas-delRío-de-la-†lataK-qeneral7elgranoD
PP
δk80-é‰-V†W7D
pure-08T-browsing
Pü
Uk8
UkP
Ukk
Ukü
mixed-0/E08Tgrazing
UF
UA
UI
U3
U6
δk80-é‰-V†W7D
We-present-a-guidelineK-listing-requirementsthat- need- to- be- met- in- order- to- be- able- toestimate- the- pathwayD ofD diageneticD
alteration- at- a- given- site- and- evaluate- thepossibility-to-reconstructDbiogenicDvalues-ofxenarthran-dental-tissue
no diverse fauna
(only xenarthrans)
diverse fauna
(taxa w/ enamel)
no sediment
available
sediment
available
sediment rare
sediment from
different specimen
ßs-has-been-shown-in-our-studyK-in-sedimentwith- high- carbonate- content- éeägä- marineconditionsD- biogenic- values- are- heavilyaltered-by-a-sedimentary-signal
high carbonate
content
low carbonate
content
conditions do not
meet requirements
conditions might
allow interpretation
Qualitative-conclusions-on-paleobiology-by-backtracking-original-valuesä
- - - Separation- between- Megatherium- and- Scelidotherium- increasesK- Megatheriumcan- therefore- be- considered- a- more- selective- feeder- with- a- pure- 08- dietK- whileScelidotherium-might-have-incorporated-0/-plantsä
AcknowledgmentsD
zor-providing-samples-and-additional-data-as-well-as-for-lab-assistance-and-for-fruitful-discussionsK-%-would-like-to-thank-†hW-student-íartin-0otte kand-supervisor-†rofä-Wrä-~ervé-7ocherenskK8-and-the-entire-7iogeology-workgroupä-Thanks-to-†rofä-Ronny-Schönberg P--and-Wrä-~einrich-TaubaldP-forenabling-%RíS-analysisK-as-well-as-7ernd-SteinhilberP-for-his-lab-workä-The-ßrgentina-†roject-is-funded-by-the-Weutsche-zorschungsgemeinschaftéWzq-qX†R%S-CPkFkAk/3/D
k
-Wepartment-of-qeosciencesK-7iogeologyK-University-of-TübingenK-~ölderlinstraße-kPKIPüI/-TübingenK-qermany
P
-Wepartment-of-qeosciencesK-%sotope-qeochemistryK-University-of-TübingenK-Wilhelmstraße-63KIPüI/-TübingenK-qermany
8
-Senckenberg-0enter-for-~uman-Xvolution-and-†alaeoenvironment-é~X†DK-Xberhard-+arls-Universität-TübingenReferences
ßll-images-or-image-materialK-unless-otherwise-indicatedK-are-taken-from-the-Wikimedia-0ommons-under-the-terms-of-the-q‰U-zree-Wocumentation-"icenseä-The-picture-of-the-grassK-leavessand-and-thermometer-are-modified-clipart-material-from-Vfficeäcomä-The-picture-of-the-%RíS-is-from-the-%sotope-qeochemistry-webpageK-the-picture-of-"estodon-and-Scelidotherium-arefrom-wwwädeviantartäcom-éuser.-fotostomiasK-XstorD