Pliocene vertebrate locality of Calta, Ankara, Turkey. 11. Isotopic investigation

Hervé BOCHERENS Laboratoire de Biogéochimie isotopique, CNRS-UPMC-INRA UMR 7618,

Université Pierre-et-Marie-Curie, Case Postale 120, 4 Place Jussieu, F-75252 Paris cedex 05 France

bocheren@ccr.jussieu.fr

Sevket SEN Laboratoire de Paléontologie, URA 12 du CNRS, Muséum national d'Histoire naturelle,

8 rue de Buffon, F-75231 Paris cedex 05 (France) sen@cirms1 .mnhn.fr

K E Y W O R D S

C-13 , carbonate apatite,

mammals , 0 - 1 8 ,

paleodiet, Pliocene,

Turkey.

B o c h e r e n s H. & S e n S . 1 9 9 8 . — I s o t o p i c i n v e s t i g a t i o n , in S e n S . ( e d . ) , P l i o c e n e v e r t e b r a t e

l oca l i t y of Q a l t a , A n k a r a , T u r k e y . 1 1 , Geodiversitas 2 0 (3 ) : 4 8 7 - 4 9 5 .

A B S T R A C T

Carbon and oxygen stable isotopic abundances of fossil mammals can provide valuable palaeoenvironmental information, provided that diagenesis did not alter the biogenic signal beyond recognition. An isotopic investigation of mammal bones and teeth from (^alta (Pliocene, Turkey) demonstrates that enamel can be used for palaeoenvironmental reconstruction, but that a diage-netic signal has been overprinted on dentine and bone. By comparison with the results of similar studies on the Miocene Turkish sites of Pasalar and Kemiklitepe, it appears that the environment of Calta was open and proba­bly steppic, a conclusion in agreement with the study of rodent faunas.

M O T S C L E S

C-13 , carbonate aparite,

mammifères, 0 - 1 8 ,

paléodiète, Pliocène, Turquie .

R É S U M É

Le gisement de vertébrés pliocenes de Çalta, Ankara, Turquie. 11. Investigation isotopique. Les abondances isotopiques en carbone et en oxygène des os et des dents de mammifères fossiles peuvent appotter des informations concernant les paléoenvironnements, à condition que la diagenèse n'ait pas altéré le signal biogénique. Une étude isotopique d'os et de dents de mammifères de Çalta (Pliocène, Turquie) montre que l'émail peut être utilisé pour les reconstitutions paléoenvironnementales, mais qu'un signal diagénétique s'est surimposé sut la dentine et l'os. Par comparaison avec les résultats d'études similaires menées sur les sites du Miocène de Turquie de Pasalar et Kemiklitepe, il apparaît que l'environnement de Çalta était ouvert et proba­blement steppique, une conclusion en accord avec les résultats de l'étude des faunes de rongeurs du site.

GEODIVERSITAS • 1 9 9 8 • 2 0 ( 3 ) 487

Bocherens H. & Sen S.

INTRODUCTION

Palaeoenvironmental reconstruction is one of the goals of the study of fossil vertebrates. During their lifetime, vertebrates record in their tissues geochemical data linked to their environment. One case pa r t i cu la r ly relevant for vertebrate palaeontology is the fact that the carbonate ions incorporated within the apatitic lattice of bone and tooth minerals are in isotopic equil ibrium with the bicarbonate in circulating blood serum. Thus, the isotopic signatures of carbon and oxy­gen of these ions are linked to dietary and envi­r o n m e n t a l p a r a m e t e r s at the t i m e of t he i t incorporation, such as the kind of plants at the beginning of the food web and the or igin of drinking water (Krueger & Sullivan 1984; Lee-T h o r p 1 9 8 9 ; Boche rens & M a r i o t t i 1 9 9 2 ; Iacumin et al. 1996). Provided that these isotopic signatures have not been altered during diagene-tical processes, they represent potential tools that can be used to decipher dietary habits and life e n v i r o n m e n t s of fossi l s p e c i m e n s . S o m e examples of studies using this approach are the d e t e t m i n a t i o n of d i e t d i f f e rences in two Pleistocene baboon species (Lee-Thorp et al. 1 9 8 9 ) , and the changes in vege ta t ion cover during the Cenozoic in Pakistan (Quade et al. 1992) and in South America (MacFadden et al. 1994) . By using isotopic variations recorded in different teeth from the same fossil individuals in some favorable cases, it is even possible to get information on dietary and/or environmental changes that occurred during the individual life­time (Koch etal. 1989).

Isotopic investigations have already been perfor­med in Turkish Cenozoic faunas, i.e. the middle Miocene fauna of Pasalar (Quade et al. 1995) and the la te M i o c e n e fauna of K e m i k l i t e p e (Bocherens et al. 1994b). In this context, it was interesting to perform an isotopic study of the Pliocene fauna of Calta.

MATERIAL AND M E T H O D S

The fossiliferous locality is close to the village of Ca l t a , a round s ixty k i lomete r s nor thwest of Ankara, in centtal Turkey. A first mention about

this site is to be found in Ozansoy (1955) . The site has yie lded a rich vertebrate fauna in the 1970's (Ginsburg et al. 1974; Sen et al. 1974; Sen 1977, this volume). The age of the locality is Pliocene (Sen 1977). Tooth dentine and enamel, bone and sediment samples have been analyzed isotopically, inclu­ding specimens belonging to species with herbi­vorous (Giraffa, bovid and Hipparion heintzi) and carnivorous (a hyenid, Chasmaportetes and a racoon-dog, Nyctereutes) habits. The choice of these two kinds of specimens have been dictated by the report of differences in the catbon isoto­pic abundances in herbivores and carnivores from temperate and cold areas (Bocherens & Mariotti 1992) , although such differences have not been observed in South Africa (Si l len & L e e - T h o r p 1 9 9 4 ) . I so top i c a b u n d a n c e s of enamel , and of bone and dent ine , have been compared in order to check for diagenetic altera­tion since dentine and bone are much less stable to diagenetic alteration than enamel (Lee-Thorp & van der Merwe 1987; Koch et al. 1990) P r e p a r a t i o n of b o n e a n d t o o t h c a r b o n a t e hydroxylapatite has been performed according to the protocol used by Lee-Thorp (1989) , modi­fied according to Bocherens et al. ( 1 9 9 1 ) . All samples were cleaned and enamel was separated from dentine using a dentist wheel. The powde­red teeth were treated with 1 M acetic acid-Ca acetate buffer for twenty-four hours to leach dia­genetic carbonate minerals, and then rinsed with distilled water several times. They were reacted with 100% phosphoric acid at 50 °C for twelve hours. The evolved carbon dioxide was purified by cryogenic distillation in a vacuum line and introduced in a VG SIRA 9 gas source isotopic ratio mass spectrometer for measurement of its c a r b o n a n d o x y g e n i s o t o p e c o m p o s i t i o n s . Carbon dioxide was extracted from the sediment samples the same way. Isotopic abundances are normalized to internat ional laboratory calcite standards analyzed concurrently with the apatite samples. The delta value for each isotope is cal­culated as 8 E X = [(Rsample / Rsample) - 1] X 1000,

where 8 E X = 8 1 3 C or 5 l s O , and R = 1 3 C / 1 2 C or 1 8 0 / 1 6 0 , respectively. The standards are PDB for carbon and S M O W for oxygen. Analytical preci­sion was better than 0 .1%o for 8 1 3 C and 0 .2%o

488 GEODIVERSITAS • 1 9 9 8 • 2 0 ( 3 )

Isotopie investigation o f the Pl iocene o f C a l t a

S e d i m e n t LI C a r n i v o r e e n a m e l I C a r n i v o r e d e n t i n e

O H e r b i v o r e e n a m e l 9 H e r b i v o r e d e n t i n e • H e r b i v o r e b o n e

- 1 4 - 1 2 - 1 0 - 8 - 6 - 4 - 2

5 13 C

FIG. 1. — V a r i a t i o n s of c a r b o n a t e h y d r o x y l a p a t i t e 5 1 3 C a n d 8 1 S O v a l u e s b e t w e e n d i f f e r e n t m i n e r a l i z e d t i s s u e s o f s i n g l e i n d i v i d u a l s

a n d s p e c i e s in Q a l t a .

for 8 l s O values. Since the correction formula is RESULTS not known for oxygen in carbonate hydroxylapa­ti te, the correction formula for calcite at the The results of isotopic analyses are presented in same temperature was used (Koch et al. 1989). table 1. In the sediment, the 8 1 3 C and the 8 1 8 0

GEODIVERSITAS • 1 9 9 8 • 2 0 ( 3 ) 489

B o c h e r e m H. & Sen S.

C a l t a

C

1 1 H

1

S a v a n n a , s o u t h w e s t e r n

C a p e , S o u t h A f r i c a

c

— f — H

+

C o l d a n d t e m p e r a t e

a r e a s

( E u r o p e , S i be r i a a n d

n o r t h w e s t e r n N o r t h

A m e r i c a )

c

— 1 — H

1

~1 1 1 1 1 1 1 1 - 1 7 - 1 6 - 1 5 - 1 4 - 1 3 - 1 2 - 1 1 - 1 0

8'3 C (%.)

FIG. 2 . — V a r i a t i o n s of c a r b o n a t e h y d r o x y l a p a t l t e 8 1 3 C v a l u e s a c c o r d i n g t o t r o p h i c l eve l in Q a l t a ( e n a m e l ) , m o d e r n S o u t h A f r i c a n

s a v a n n a (S i l l en & L e e - T h o r p 1 9 9 4 ) a n d m o d e r n c o l d a n d t e m p e r a t e a r e a s ( B o c h e r e n s & M a r i o t t i 1 9 9 2 ) .

values range from - 9.2 to - 3.0%o and from 21.9 to 23.3%o respectively. The 8 1 3 C value of Hipparion bone is — 8.4%o, S 1 3 C values in denti­ne range from - 9.8 to - 8.9%o in herbivores and from — 7.3%o to - 9.6%o in carnivores, whereas 8 l s O value is 27.4%o in Hipparion bone, and 8 1 8 0 values range from 26.5 to 30.1%o in denti­ne and from 23.4 to 31.4%o in enamel.

DISCUSSION

An ecological intetpretation of the measured iso-topic abundances is possible only if the biogenic values have not been significantly alteted by dia-genetical processes. Thus the first part of the dis­cussion will deal with diagenetic aspects of the tesults, wheteas the second part will discuss pos­sible implications.

PRESERVATION OF BIOGENIC ISOTOPIC A B U N ­

DANCES

Two approaches can be used to es t imate the degree of possible alteration of the isotopic abun­dances: the isotopic differences between altered (bone, dentine) and possibly non altered tissues

(enamel), and the disruption of biogenic isotopic signals, such as the difference between herbivores and carnivores. Plotting the differences in the S 1 3 C and the 8 l s O values of bone, dentine and enamel in the same specimens fot the different analyzed species clearly shows that dentine 8 1 3 C values are systematically less negative than those of enamel of the same specimens, whereas 8 l s O values tend to be less scattered for dentine than for enamel (Fig. 1). Since the sediment 8 1 3 C values are less negative than those of all enamel samples, an altetation of the biogenic carbon isotopic composition would lead to an increase of the resulting 8 1 3 C values, which is the case for the 8 I 3 C values measured in dentine when compared to those measured in enamel of the same teeth, and this increase is even more important in the case of Hipparion bone, relative to dentine. In the case of oxygen, the 8 1 8 0 values of sediment are lower than those of enamel. However, not all dentine 8 1 8 0 values appear lower than those of the enamel of the same tooth. Some are roughly equal {Hipparion and hyena) , and one is clearly higher (racoon-dog). It looks as if the dentine 8 I 8 0 values tend to reach an average 8 l s O value close to 26%o,

490 GEODIVERSITAS • 1 9 9 8 • 2 0 ( 3 )

Isotopie investigation o f the Pl iocene o f Ca l ta

TABLE 1 . — 8 1 3 C a n d 8 1 8 0 v a l u e s o f s a m p l e s f r o m C a l t a . D u e to t h e s m a l l s i z e of t h e t e e t h , t h r e e s p e c i m e n s h a v e b e e n p o o l e d t o g e ­

t h e r in t h e c a s e of Nyctereutes. E n a m e l v a l u e s p r e s e n t e d in b o l d h a v e b e e n u s e d f o r f i g u r e 3 .

S a m p l e T a x o n P i e c e N u m b e r S 1 3 C 5 1 8 0 S a m p l e CX.) (%.)

S e d i m e n t 1 0 0 5 0 0 - 9 . 2 23 .3 C a r b o n a t e d c o n c r e t i o n 1 0 0 6 0 0 - 7 . 5 22 .8 f r o m p a l a e o s o i l C a r b o n a t e d 1 0 0 7 0 0 - 3 . 0 21 .9 h y m e n o p t e r e nes t G i ra f fe Giraffa sp . e n a m e l 1 0 0 8 0 0 - 1 2 . 0 31 .4 Giraffa sp .

d e n t i n e 1 0 0 8 0 0 - 9 . 7 30.1 B o v i d B o v i d a e indet . e n a m e l 1 0 0 9 0 0 - 1 1 . 4 31 .4

d e n t i n e 1 0 0 9 0 0 - 8 . 9 26 .8 H y e n a Chasmaportetes sp . e n a m e l 1 0 1 0 0 0 - 1 1 . 8 26 .5

d e n t i n e 1 0 1 0 0 0 - 9 . 6 26 .5 R a c o o n - d o g Nyctereutes sp . e n a m e l (3) 1 0 1 1 0 0 - 1 0 . 6 23 .4

d e n t i n e (3) 1 0 1 1 0 0 - 7 . 3 26 .8 H ippa r i on Hipparion heintzi e n a m e l 1 0 3 4 0 0 ( A C A - 2 5 5 ) - 1 0 . 4 27 .2

d e n t i n e 1 0 3 4 0 0 ( A C A - 2 5 5 ) - 9 . 6 27 .3 H i p p a r i o n Hipparion heintzi e n a m e l 1 0 3 5 0 0 ( A C A - 2 6 6 ) - 1 0 . 5 27 .2

d e n t i n e 1 0 3 5 0 0 ( A C A - 2 6 6 ) - 9 . 8 27 .3 H i p p a r i o n Hipparion heintzi b o n e 1 0 3 6 0 0 ( A C A - 9 8 ) - 8 . 4 27 .4

around 3%o higher than the value of sediment carbonate. It appears thus that only enamel iso-topic composit ion can eventual ly be used for palaeobiological reconstruction, in agreement with previous studies (Wang & Ceding 1994). T h e S 1 3 C values of herbivore and carnivore enamel do not appear different, which is similar to wha t is observed in modern South Africa (Sillen & Lee-Thorp 1994) but different from what is observed in modern and Pleistocene Europe (Bocherens & Mariotti 1992; Bochetens et al. 1994a) . However, the absolute values are less negative in the Cal ta samples than in the modern South African ones. This could be due to the deple t ion in 1 3 C recorded in modern atmospheric C 0 2 that result from the industrial development since 150 years (Friedli et al. 1986), as suggested by Lee-Thorp (submitted). This last author considers that modern values should be shifted by 1.5%o (less negative) before compari­sons are made with 8 1 3 C values measured on fos­sils. After such a correction, the Calta values still appear less negative than the South Aftican ones, but the difference is not very large. Moreover, the 8 1 3 C values measured on Calta samples appear just slightly higher than those of modern herbi­vores from temperate and arctic environments,

and very similar if a 1.5%o increase is considered for modern values. Thus, the 8 1 3 C values measu­red on Calta samples do not appear conttadic-tory with data gathered from modern environ­ments. As far as enamel 8 I 8 0 values are concerned, the comparison with modern biogenic signals is not as straightforward as for carbon. A clear differen­ce was demonstrated for hippopotamuses relative to terrestrial herbivores, in modern and fossil e n v i r o n m e n t s ( B o c h e r e n s et al. 1 9 9 6 ) . Unfortunately, no hippopotamus has been found at Calta. Another isotopic particularity found in modern hetb ivores is h igher 8 1 8 0 values in giraffes relative to other herbivores, probably due to their dietary and drinking habits (Quade et al. 1995). It is noteworthy that among Calta hetbi­vores, the giraffe specimen present the highest 8 1 8 0 value (Table 1). Finally, lower 8 l s O values have been reported for carnivores relative to her­bivores among modern mammals from Kenya (Ambrose 1 9 9 2 ) . A l t h o u g h the n u m b e r of samples is low, both Cal ta carnivores present lower 8 l s O values than any analyzed herbivore from the site (Table 1).

Since no expected biogenic signal indicate signi­ficant alteration of in vivo isotopic signatures, it

GEODIVERSITAS • 1 9 9 8 • 2 0 (3) 491

Bocherens H. & Sen S.

3 4

3 3 H

3 2 H

31 A

3 0

2 9

2 8

2 7

2 6 - J

2 5 H

2 4 - \

2 3 -H

2 2

21 -I

2 0

• 1 5

• •

Hypsodontus

Giraffokeryx

Choerolophodon

Anchitherium

• 0

Hipparion

b o v i d

Gomphotherrium

Caprotragoides

- 14

1

- 13

1

- 1 2

8 , 3 C (%„)

I

- 1 0

Ç a l t a

• Giraffa

• b o v i d

O Hipparion

P a s a l a r

j | a v e r a g e ± 1 s . d .

K e m i k l i t e p e

J ~J a v e r a g e ± 1 s . d .

S Samotherium

F i g . 3 . — C a r b o n a n d o x y g e n i s o t o ­p ie a b u n d a n c e s in e n a m e l c a r b o n a ­te h y d r o x y l a p a t i t e o f M i o c e n e a n d P l i o c e n e h e r b i v o r e s f r o m T u r k e y ( v a l u e s f r o m t a b l e 2 ) .

is l eg i t ima te to assess some pa laeobio log ica l impl ica t ions of these isotopic composi t ions , which will be done in the next section.

PALAEOBIOLOGICAL IMPLICATIONS OF ISOTOPIC

SIGNATURES

The carbon isotopic compositions of all the spe­cimens indicate that no C4 grasses were present

in their dietary components. This situation is s i m i l a r to m o d e r n cen t ra l A n a t o l i a , w h i c h belongs to the Euro-Siberian phytogeographic region (Klein 1994). It is noteworthy that colla­gen carbon isotopic abundances in modern her­bivores from Turkey showed no evidence of C4 grasses consumption either (Bocherens 1992). The isotopic differences between herbivorous

492 GEODIVERSITAS • 1 9 9 8 • 2 0 (3)

Isotopie investigation o f the Pl iocene o f Cal ta

TABLE 2 . — A v e r a g e v a l u e s a n d s t a n d a r d - d e v i a t i o n s o f 8 1 3 C a n d 8 1 8 0 v a l u e s o f t e r r e s t r i a l h e r b i v o r e e n a m e l f r o m P a s a l a r a n d

K e m i k l i t e p e u s e d f o r f i g u r e 3 . P a s a l a r d a t a a r e f r o m Q u a d e e f a/. ( 1995) a n d K e m i k l i t e p e v a l u e s a r e f r o m B o c h e r e n s e f al. ( 1 9 9 4 b ) .

S i t e T a x o n g r o u p n S 1 3 C 8 1 8 0 (%.) (%.)

P a s a l a r Hypsodontus pronaticornis b o v i d 5 - 1 0 . 3 1 0 . 3 2 7 . 3 + 1.6 P a s a l a r Gomphotherium pasalarense m a s t o d o n t 4 - 1 1 . 4 ± 0 . 4 2 4 . 6 ± 0 .9 P a s a l a r Giraffokeryx aff. punjabiensus g i ra f fe 4 - 1 2 . 7 1 0 . 5 3 0 . 3 ± 2 .5 P a s a l a r Anchitherium aurelianense e q u i d 3 - 11 .4 ± 0 . 5 25 .2 ± 0 . 7 P a s a l a r Caprotragoides stehlini b o v i d 4 - 1 2 . 7 ± 0 . 4 2 3 . 4 ± 1.4 K e m i k l i t e p e Choerolophodon sp . m a s t o d o n t 3 - 1 1 . 2 ± 0 . 1 26 .9 ± 0 . 3 K e m i k l i t e p e Hipparion sp . e q u i d 4 - 1 0 . 4 ± 0 . 6 26 .1 ± 0 . 7 K e m i k l i t e p e Samotherium sp . g i ra f fe 1 -10.1 27 .8 K e m i k l i t e p e bov id sp . bov id 3 - 1 0 . 5 ± 0 . 5 2 5 . 8 ± 2 . 1

taxa can provide palaeoenvironmental informa­t ion . T h e i so topic inves t iga t ion of the r ich Pasalar fauna has shown that terrestrial herbivo­rous cluster according to their taxonomic affini­ties (Quade et al. 1995). It seems that a tendency can be drawn from low 8 I 3 C and 8 1 8 0 values to higher 8 1 3 C and 8 1 8 0 values (Table 2, Fig. 3 ) . This tendency could reflect the fact that plants wi th low 8 1 3 C values are those from closed-canopy forests, where high humidi ty maintains low 8 l s O values in herbivores whereas plants with higher 8 I 3 C values are characteristic of open environments, where more evaporation in plants lead to increased 8 1 8 0 values in leaf water, and consequently in herbivores feeding on such plant material (Quade et al. 1995). One notable excep­t ion to this pa t t e rn is the case of b rows ing giraffes, wi th low 8 1 3 C values and high 8 I 8 0 values, such as Giraffokeryx from Pasalar and Giraffa from Calta (Fig. 3 ) . This singular pattern can nonetheless be explained by high evaporation in top canopy leaves eaten by gitaffes (Quade et al. 1 9 9 5 ) . It is no tewor thy that the giraffid Samotherium does not fit into this pattern, but this genus has been recognized as less specialized in browsing than typical giraffes (Solounias et al. 1988). The isotopic composition of the different taxa of Calta herbivores fit to this pattern defi­ned from Pasalar and Kemiklitepe studies, and more particularly to the most open environmen­tal pole of the pattern (Fig. 3 ) . The conclusion based on isotopic biogeochemistry of an open environment in C a h a is in agreement with the conclusions based on the high proport ion of rodents adapted to steppic and open environ­

ments, such as Pseudomeriones and Pliospalax and on the low proportion of murids (Sen 1977), as well as on the low number of Soricidae species (Reumer this volume). It is interesting to notice that the analyzed hipparions belong to the robust species H. heintzi, described as a subunguligrade walking on a soft soil in an arid context rather t han to h u m i d c o n d i t i o n s ( E i s e n m a n n & S o n d a a r th is v o l u m e ) . T h e i so top ic resu l t s confirm that the analyzed individuals experien­ced an open environment with arid conditions. The occurrence of the Suidae Sus arvernensis in Calta is interpreted as reflecting a forested envi­r o n m e n t ( G u e r i n et al. t h i s v o l u m e ) . Unfortunately, it was not possible to perform iso­topic measurements on enamel from this species, which could have allowed to verify that the suid specimens from C a l t a actually lived in a forested environment.

It is difficult to compare these isotopic abun­dances in terms of global climatic changes from the lower Miocene to the Pliocene because of the large variations of 8 1 8 0 values between different samples from a same site. The micro-environ­mental factors seem to have a large influence on the oxygen isotopic abundances of fossil mam­mals. In order to prevent this phenomenon to bias the climatic record, it should be necessary to select a given taxon with well-known relation­ships between the 8 I 8 0 values in meteoric waters and those of enamel apatite. An additional com­p l i c a t i n g factor is the necess i ty to work on enamel due to the poor stability of bone during fossil ization. Unfor tunately , enamel presents significant isotopic variations from one tooth to

GEODIVERSITAS • 1 9 9 8 • 2 0 ( 3 ) 493

Bocherens H. & Sen S.

the other, or even within one tooth, due to the

fast mineralization of this tissue, which records

environmental parameters during a brief instant

of the individual lifetime (Bryant et al. 1996;

Lee-Thorp et al. 1997). However, this problem

can be turned into an advantage in the case of

studying short-term climatic variations, such as

seasonal changes.

CONCLUSIONS

T h e i so top ic b i o g e o c h e m i s t r y of ca rbona te hydroxylapatite of Pliocene mammals from Çalta shows tha t o n l y e n a m e l can be u s e d for palaeoenvironmental reconstructions, and that herbivorous taxa indicate an open environment, with a rather important évapotranspiration in plants. These conclusions are in total agreement wi th those based on the s tudy of the rodent fauna.

Acknowledgements Thanks are due to D. Billiou for technical assis­tance in the isotopic analyses of Çalta samples. The manuscript was improved through the com­ments of the reviewers, namely Dr. P. Andrews and Dr. T E. Ceding.

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Submitted for publication on 10 July 1997; accepted on 9 January 1998.

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