Early miocene climate of Central Eurasia — Evidence from Aquitanian floras of Kazakhstan

Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32 – 48 www.elsevier.com/locate/palaeo

Early miocene climate of Central Eurasia — Evidence from Aquitanian floras of Kazakhstan Angela A. Bruch a,⁎, Sergey G. Zhilin b a

Senckenberg Research Institute and Natural History Museum, Senckenberganlage 25, D-60325 Frankfurt a.M., Germany b Komarov Botanical Institute, Department of Palaeobotany, 2 Prof. Popov Street, 197376 St. Petersburg, Russia Received 15 February 2006; received in revised form 21 November 2006; accepted 24 November 2006

Abstract The rich fossil record in Kazakhstan documents that during the Oligocene and Early Miocene this area in Central Eurasia was densely forested with warm-temperate deciduous trees and shrubs of the so-called “Turgayan flora”. Twenty-nine fossil floras (leaf and pollen assemblages) have been selected for a quantitative analysis of the Aquitanian (early Early Miocene) climate in Kazakhstan. Mean annual temperatures are estimated to have been around 15 °C, while values of mean annual precipitation are about 1000 mm. In combination with several other climate parameters estimated (temperatures of the warmest and coldest months, precipitation of the wettest, driest and warmest months), these data reflect uniform climatic conditions over several thousands of square kilometres. Temperature parameter estimates show slight spatial differentiation, with generally cooler mean annual temperatures and higher seasonality (i.e. warmer summers and colder winters) in the north-eastern part of the study area compared with the southwestern area around Lake Aral. As compared with palaeoclimate estimates for the European and East Asian Aquitanian, the central part of the Eurasian continent reveals higher seasonality and slightly increased continentality. © 2006 Elsevier B.V. All rights reserved. Keywords: Kazakhstan; Early Miocene; Flora; Leaves; Pollen; Palaeoclimate

1. Introduction Kazakhstan is geographically situated in the mid latitudes of Central Eurasia, east of the Caspian Sea and northwest of the Himalayan mountain chain with almost no geomorphological barriers towards the north (Fig. 1). Due to its geography and typically for Central Eurasia, the present day climate in Kazakhstan is dominantly characterized by a strong continental influence with a high seasonality of temperature, high latitudinal gradients

⁎ Corresponding author. Tel.: +49 69 97075 604; fax: +49 69 97075 137. E-mail addresses: [email protected] (A.A. Bruch), [email protected] (S.G. Zhilin). 0031-0182/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2006.11.014

of temperature, and an overall low annual precipitation (cf. Fig. 2). Whereas summer temperatures can reach up to 36 °C (daily mean) with a July monthly mean between 20 and 28 °C, winter temperatures are below −20 °C even in the lowlands with a January monthly mean between −1 and −22 °C (Rivas-Martinez, 1996-2005). Summer and winter temperatures, as well as mean annual temperature show a strong latitudinal gradient. In contrast, in the whole of Kazakhstan precipitation hardly exceeds 400 mm per year (Rivas-Martinez, 1996–2005; Mühr, 2000–2005). Due to these climatic conditions, and anthropogenic influences, the landscape in Kazakhstan is largely covered by southern steppe vegetation generally dominated by herbs and shrubs, and to a lesser extent also by forest-steppe, semi desert and desert.

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Fig. 1. Geographic map with the positions of the studied floras.

In contrast to the present-day situation, the rich fossil plant record documents that during the Oligocene and Early Miocene the Kazakhstan plain was densely forested with temperate deciduous trees and shrubs of the socalled “Turgayan flora”, which is regarded as the precursor of the modern temperate floras of the Northern Hemisphere. The Turgayan flora originally spread from

Fig. 2. Climatic diagram of the town of Turgay after Mühr (20002005). Turgay is situated in the central part of Kazakhstan (49.62°N, 63.5°E) with climate conditions typical for the country: a strong annual range of temperature and generally low precipitation.

Central and Northern Asia during the Oligocene and covered vast areas in the high and mid-latitudes of Central Eurasia at the beginning of the Early Miocene (Zhilin, 1989, 2002; Nikitin, 2005). For a general understanding of the Neogene history of the Eurasian vegetation and of the modern temperate flora of Europe it is crucial to identify the causes of the distribution of the Turgayan flora. These causes may be manifold, including palaeogeography (e.g. retreat of Tethys and Eastern Paratethys, beginning of mountain uplift of the Himalayan chain) and palaeoclimate (Neogene cooling). To unravel these causes and to answer the question to what extent the pathways of the Turgayan flora have been influenced by the climatic development of the Neogene, it is necessary to obtain terrestrial palaeoclimatic data for the whole of Eurasia and especially for Kazakhstan. As a first step towards this aim we will present detailed flora lists and quantitative palaeoclimatic data for the Kazakh floras of Aquitanian age (early Early Miocene, 23.03– 20.34 Ma; Gradstein et al., 2004) in this study, discuss their regional implications, and compare them with what is known from other parts of Eurasia. 2. The Turgayan flora The Turgayan flora is a temperate flora which is characteristic for the Chattian and Aquitanian of northern

Sample name

Akmola 1 Altyn–Shokysu II Altyn–Shokysu IV Altyn–Shokysu VI Ashutas–I Bol'shoj Log Ovrag I Ovrag II Ovrag III Ovrag V Pozadi Ovrag II Sloj–1 Sloj-2 Sloj-3 Sloj-4 Berdy Chiliktysor-II-IV Erzhilansay 1 Kinjak 1a Kinjak 1b Kinjak 2a Kinjak 2b Kintykche 1a Kintykche 1b Krugloye-all Mynsualmas 1 Mynsualmas 2 Nausha 1

Locality name

Akmola Altyn–Shokysu Altyn–Shokysu Altyn–Shokysu Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Berdy Chiliktysor Erzhilansay Kinjak Kinjak Kinjak Kinjak Kintykche Kintykche Krugloye Mynsualmas Mynsualmas Nausha

a

Dzhezkazgan District Kzyl–Orda District Kzyl–Orda District Kzyl–Orda District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East–Kazakhstanian District East-Kazakhstanian District East-Kazakhstanian District East-Kazakhstanian District Dzhezkazgan District Aktyubinsk District Kustanay District NW Karakalpakia NW Karakalpakia NW Karakalpakia NW Karakalpakia Aktyubinsk District Aktyubinsk District Kustanay District Mangyshlak District Mangyshlak District Kustanay District

Administrative district 65.68 61.14 61.25 61.00 85.52 85.52 85.52 85.52 85.52 85.52 85.52 85.52 85.52 85.52 85.52 65.38 60.54 65.38 58.52 58.52 58.52 58.52 58.67 58.67 61.67 55.62 55.62 64.12

Longitude 48.81 47.61 47.63 47.61 48.03 48.03 48.03 48.03 48.03 48.03 48.03 48.03 48.03 48.03 48.03 49.18 47.31 49.20 45.53 45.53 45.53 45.53 45.78 45.78 51.46 45.65 45.65 48.83

Latitude Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Outcrop Drilling Outcrop Outcrop Outcrop

Type of sample

Table 1 List of localities used for climate analyses (a) geography (longitude and latitude in decimal degree) and (b) stratigraphy and references

Whole flora Western part of lens Eastern part of lens Whole flora

Whole flora Upper part of outcrop Upper part of outcrop Lower part of outcrop Lower part of outcrop

Whole flora Central part of site Eastern part of site Western part of site Whole flora Ravine “Bol'shoj log”, 1 km west of profile III Ravine I, westernmost profile, 3.5 km W of profile III Ravine II, ca. 550 m east of profile I Ravine III, easternmost profile Ravine V, ca. 500 m west of profile III East of profile II Sample 1 from profile “East of Bolshoj Log” Sample 2 from profile “East of Bolshoj Log” Sample 3 from profile “East of Bolshoj Log” sample 4 from profile “East of Bolshoj Log”

Remarks

34 A.A. Bruch, S.G. Zhilin / Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32–48

Type of flora

Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Pollen Leaves Pollen Leaves Pollen Leaves Leaves Leaves Leaves

Sample name

Akmola 1 Altyn-Shokysu II Altyn-Shokysu IV Altyn-Shokysu VI Ashutas-I Bol'shoj Log Ovrag I Ovrag II Ovrag III Ovrag V Pozadi Ovrag II Sloj-1 Sloj-2 Sloj-3 Sloj-4 Berdy Chiliktysor-II-IV Erzhilansay 1 Kinjak 1a Kinjak 1b Kinjak 2a Kinjak 2b Kintykche 1a Kintykche 1b Krugloye-all Mynsualmas 1 Mynsualmas 2 Nausha 1

b

Lignitic clay Lignitic clay Lignitic clay Sandstone Linitic clays, clay, sandy clay Sandy clays Lignitic clay Lignitic clay Clays Coloured clays Purpel clay lense within sandst. Clays Greyish clays Brownish clays Ferrous red and purple clays Lignitic clay Lignitic clay Lignitic clay Lignitic clay Lignitic clay Lignitic clay Lignitic clay Lignitic clay Lignitic clay Light-gray silty clay Lens of sandstone Lens of sandstone Lignitic clay

Sediments Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Fluviatile Marine Marine Marine Marine Marine Marine Fluviatile Marine Marine Fluviatile

Environment Kaidagul Suite Chagray Suite Chagray Suite Chagray Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Oshagandy Suite Kaidagul Suite Chagray Suite Kaidagul Suite Baygubek Suite, Bg2 Baygubek Suite, Bg3 Baygubek Suite, Bg4 Baygubek Suite, Bg5 Baygubek Suite, Bg6 Baygubek Suite, Bg7 Kaidagul Suite Baygubek Suite Baygubek suite Kaidagul suite

Local stratigraphic unit Floristics, geology Floristics Floristics Floristics Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Floristics, geology Marine molluscs Marine molluscs Marine molluscs Marine molluscs Marine molluscs Marine molluscs Floristics, geology Marine molluscs Marine molluscs Floristics, geology

Correlation method (Kornilova, 1950; Kirichkova, 1955; Zhilin, 1989) Andrejev (1991) Andrejev (1991) Andrejev (1991) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) (Iljinskaja, 1957; Zhilin, 1989) Zhilin this study (Zhilin, 1974, 1989) (Zhilin, 1989, 1991; Nigmatova, 1998) (Zhilin, 1974; Zhilin, 1989) Zhilin (1974) Zhilin (1974) Zhilin (1974) Zhilin (1974) Zhilin (1974) (Zhilin, 1989; Zhilin and Samsonov, 1999) Zhilin (1974) Zhilin (1974) (Shilin and Tokar', 1971; Zhilin, 1989)

References

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and central parts of Kazakhstan and the south of Western Siberia (Zhilin, 1989). The term “Turgayan flora” was proposed by A.N. Kryshtofovich (1928) who modified it many times. In his last article, Kryshtofovich (1955) interpreted the Turgayan flora very broadly as the entire temperate flora of the past, extending his concept over the whole of Eurasia and parts of North America. Later, thorough examination of new data permitted a detailed definition of the Turgayan flora in the Oligocene– Aquitanian of Turgay and other areas of Kazakhstan as an individual palaeophytogeographical subdivision (Zhilin, 1989, 1991, 2002). The Turgayan flora appeared during the early Cenozoic in Asia. During the Oligocene it spread to Central Eurasia and replaced “the Drevlyanian flora” of the Eocene (the Drevlyanian, after Zhilin, 1989 = the Poltavian, after Kryshtofovich, 1928, a. o.). The appearance of the Turgayan flora in Kazakhstan coincides with the beginning of the Oligocene. During the Early Oligocene the floras of Turgayan type, although they were generally temperate, differ extremely in different areas of Kazakhstan (Zhilin, 2005). Only during the Late Oligocene, in the Chattian, the Turgayan flora became more homogeneous. Nevertheless, in the most homogeneous Aquitanian phase there also exist some examples of different local floras mainly due to different taphonomic situations. For instance, the localities Kinjak 1 and Kinjak 2 are very closely located, but show very different compositions of species. Since Kinjak 1 is composed of organic sandy clay of shallow marine origin whereas Kinjak 2 confirms a deeper marine environment with dark blue marine clay, in this case a taphonomic bias caused by transport seems to be evident. Initially, based on Kryshtofovich (1928, 1955) many authors used the term “Turgayan” only for a flora of Turgayan type that could be used for geochronological purpose, although (Zhilin, 1974, 1984, 1989) showed that the development of the Turgayan flora in Kazakhstan represents a step-wise process from Oligocene to Miocene implying some limitations to age assignment. Zhilin (2002) divided the process of formation of the flora into five phases from the end of the Late Eocene to the end of the Early Miocene. In this paper we split the fourth phase of Zhilin (2002; i.e. Chattian-Aquitatian floras) and focus only on the Aquitanian part. The Chattian and the Aquitanian floras of Kazakhstan may be distinguished by index fossil species (or indexfossils), introduced by Zhilin (1989, 1991) for this region. Earlier, the author used the term standard flora for this concept (Zhilin, 1985), which was also successfully applied to Miocene plant floras from southern Ukraine (Teslenko, 1993). However, to estimate the age of a flora

by its assemblage is only possible in cases when exceptional good (i.e. complete) collections are available. The main floristic changes on the Chattian/Aquitanian border in the region of Central and Northern Kazakhstan are related to the disappearance of previous warm-temperate taxa, such as Apocynophyllum helveticum, Cotinus lavrovii, and Fraxinus dubia (Zhilin, 1984, 1989; Kvacek and Sakala, 1999). But also some new warm-temperate species appeared in the Aquitanian floras, such as Daphnogene sassafroides, Aponogeton zhilinii, Laurocerasus praeofficinalis and Cocculus kinjakensis. In addition, new temperate species came in, among them Ribes diacanthoides and Periploca kryshtofovichii. 3. Materials For a quantitative climatic investigation of the wellstudied Aquitanian floras of Kazakhstan, 29 assemblages with 26 leaf and 3 pollen floras from 11 localities have been compiled which are dated to Aquitanian (early Early Miocene, 23.03–20.34 Ma, Gradstein et al., 2004). Most of the floras have been studied in great detail by one of the authors over several decades (Zhilin, 1974, 1989, 1991, 2002). All localities and samples are listed in Table 1 together with information on their stratigraphy and sedimentology, and with references concerning the fossil floras and geology. Full taxa lists are given in Table 2 for all localities investigated. Although, for the most part the lists are already published, they may provide information on literature not easily accessible and give an entire overview on these floras for further comparisons. Additionally, a small number of minor revisions concerning mainly synonyms and the relation to nearest living relatives is provided on the published taxa by one of the authors (S.G. Zhilin). Additional information is given on the not yet published locality Berdy in the central part of Kazakhstan, which supports the stratigraphic correlation of floras from Eastern and Central Kazakhstan. All new information is clearly indicated in bold in Table 2. All data provided here are accessible by the world data base PANGAEA under DOI number: 10.1594/PANGAEA.547786. The floras from the localities Kinjak, Kintykche, and Mynsualmas, all located on the Ustjurt Plateau west of Lake Aral, are undoubtedly dated to the Aquitanian stage (Baygubekian Suite) by marine molluscs, sharks teeth, and ostracods (Zhilin, 1974). All other floras are correlated via geological or floristical extrapolations. In these cases the above mentioned index species indicate the Aquitanian age (Zhilin, 1989, 1991, 2004a). Of course, these extrapolations become progressively more difficult with increasing distance from the Ustjurt area.

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This is especially the case for the localities at Mt. Ashutas on the shore of the river Kara Irtysh in Eastern Kazakhstan located about 2000 km east of Lake Aral, where there have been some former disagreements about the stratigraphic age. Although these floras from the Oshagandy Suite were considered to be Late Oligocene in age by Iljinskaja (1986), the same author assumed the Ashutas floras to be contemporaneous to the flora of Erzhilansay (Iljinskaja, 1967). Also the new locality Berdy in the central part of Kazakhstan, which provides proof of the occurrence of Sassafras ferrettianum, supports this correlation. This species is generally rare in the Aquitanian localities of Central Kazakhstan except for Erzhilansay, but frequent in the Eastern Kazakhstan localities of Ashutas. Therefore, the locality Berdy may serve as an important floristic link between these regions, supporting the stratigraphic correlation of Erzhilansay and Ashutas. As well, Zhilin (1974, 1989) stressed the remarkable similarities between the floras from Erzhilansay and Ashutas, but also their significant correspondence with the Baygubekian floras from the Ustjurt area, which are located in marine deposits and precisely dated by marine molluscs, sharks teeth, and ostracods to be of Aquitanian age (Zhilin, 1974, 1989). Additionally, studies of palaeomagnetics on the Ashutas profiles support an Early Miocene age for the section (Yahimovich et al., 1993). 4. Methods After being compiled and partly adjusted, the Aquitanian floras have been analysed using the Coexistence Approach (CA) of Mosbrugger and Utescher (1997). This technique for quantitative terrestrial climate reconstructions in the Cenozoic using plant fossils can be applied to all kinds of fossil plant remains (i.e. leaves, fruits and seeds, pollen, wood). Based on the assumption that the climatic requirements of Cenozoic plant taxa are similar to those of their nearest living relatives (NLRs), the aim of the CA is to find the climatic ranges in which a maximum number of NLRs of a given fossil flora can coexist. These coexistence intervals– one for each climate parameter– are considered to be the best description of the palaeoclimatic conditions under which the fossil flora lived. The application of the CA is facilitated by the computer program CLIMSTAT and the database PALAEOFLORA which contains NLRs of more than 3000 Cenozoic plant taxa, together with their climatic requirements which are derived from meteorological stations located within the distribution areas of the NLRs. For a consistent interpretation of the results, relict taxa which

37

are living today in very restricted areas, are excluded from the analyses. In these cases it is evident that the NLRs do not exclusively reflect the former climatic requirements of their ancestors (for a detailed discussion see Mosbrugger and Utescher, 1997; Mosbrugger, 1999; Utescher et al., 2000; see also information given on the web site www.palaeoflora.de). In this study seven climate parameters have been considered for palaeoclimatic analysis, i.e. mean annual temperature (MAT), temperature of the coldest month (CMT), temperature of the warmest month (WMT), mean annual precipitation (MAP), highest monthly precipitation (HMP), lowest monthly precipitation (LMP) and warmest month precipitation (WMP). Additionally, the mean annual ranges of temperature and precipitation are calculated as the difference between summer and winter temperatures (mean annual range of temperature: MART = WMT − CMT) and the difference between wettest and driest month precipitation (mean annual range of precipitation: MARP = HMP − LMP). Typically, the resolution and the reliability of the resulting coexistence intervals increase with the number of taxa included in the analysis and are relatively high for floras with ten or more taxa for which climate parameters are known. Thus, no climatic data are given here for floras with less than 10 taxa or insignificantly wide coexistence intervals, i.e. coexistence intervals larger than 5 °C for MAT; then all data of that locality are excluded. The latter is the case only for the pollen flora Kinjak 2b, which results in 13.3–21.7 °C for MAT. The resolution of the calculated palaeoclimate data varies with respect to the parameter examined; it is highest for temperaturerelated parameters (MAT, WMT, CMT) where it is usually in the range of ± 1 to ± 2 °C; results for MAP reach an accuracy of ± 100 to ± 200 mm, whereas values of other parameters of precipitation (HMP, LMP, WMP) reflect mainly the overall climatic trends (see Mosbrugger and Utescher, 1997). As stated above, the CA calculates for all climate parameters coexistence intervals which are assumed to encompass the “real climate value”. For the purpose of data visualisation the centres of the calculated coexistence intervals are used in Fig. 3. An analysis of the Recent European climate by Klotz (1999; see also Pross et al., 2000) shows for subtropical to temperate conditions that the centres of the coexistence intervals correlate better to the real data than the borders of the intervals. To visualise the obtained palaeoclimate data in maps, results were processed with the GIS program ArcView. Interpolations between data points were calculated using the inverse distance weighted method, which provides a relatively smooth gradient between the

Table 2 Flora lists for all localities with Nearest Living Relatives of the fossil taxa. New information and revisions by Zhilin are indicated in bold (+ genus level added for climate analysis)

38 A.A. Bruch, S.G. Zhilin / Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32–48

(continued on next page)

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Table 2 (continued )

40

(continued on next page)

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Table 2 (continued )

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Fig. 3. Visualisation of climate results in maps for mean annual temperature (MAT), mean annual precipitation (MAP), temperature of the coldest month (CMT), temperature of the warmest month (WMT), mean annual range of temperature (MART), and mean annual range of precipitation (MARP).

single data points, giving detailed patterns between closely situated localities and less detail between localities separated by greater distances. Moreover, this procedure smoothes out strong fluctuations between close localities (e.g. Kintykche 1a and 1b) thus reducing data noise. To avoid over-interpretation of the resulting maps, the underlying data points (i.e. localities) are

clearly indicated and the interpolation is only visualised within a radius of 200 km around the localities. 5. Results The quantitative climate reconstructions for all floras comprising more than ten fossil taxa are given in Table 3

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Table 3 Results of climate analysis with the coexistence approach border and centre values of the coexistence intervals for (a) temperature and (b) precipitation parameters; l.b.: left borders of coexistence intervals, r.b.: right borders of coexistence intervals a Locality name

Sample name

Taxa total

Taxa analysed

l.b.

MAT [°C]

r.b.

l.b.

CMT [°C]

r.b.

l.b.

WMT [°C]

r.b.

Akmola AltynShokysu AltynShokysu AltynShokysu Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas Ashutas

Akmola 1 Altyn-Shokysu II Altyn-Shokysu IV Altyn-Shokysu VI Ashutas-I Bol'shoj Log Ovrag I Ovrag II Ovrag III Ovrag V Pozadi Ovrag II Sloj-1 Sloj-2 Sloj-3 Sloj-4 Berdy Chiliktysor-II–IV Erzhilansay 1 Kinjak 1a Kinjak 1b Kinjak 2a Kinjak 2b Kintykche 1a Kintykche 1b Krugloye-all Mynsualmas 1 Mynsualmas 2 Nausha 1

17 21

17 15

13.30 13.30

14.95 15.10

16.60 16.90

− 0.10 − 0.10

2.85 4.55

5.80 9.20

25.60 24.00

26.95 25.25

28.30 26.50

21

15

13.30

15.10

16.90

− 0.10

4.55

9.20

24.00

26.05

28.10

15

15

13.30

15.10

16.90

− 0.10

4.55

9.20

24.00

26.15

28.30

83 30 41 24 14 22 10

47 26 27 23 13 17 6

14.40 13.30 13.60 13.30 13.30 13.60 Not enough taxa

15.00 14.90 14.60 14.90 14.90 15.85

15.60 16.50 15.60 16.50 16.50 18.10

2.90 − 0.10 1.80 − 0.10 − 0.10 1.80

3.85 2.35 3.30 2.35 2.35 3.80

4.80 4.80 4.80 4.80 4.80 5.80

24.00 24.00 24.00 24.00 21.70 25.60

24.05 24.35 24.05 24.35 23.20 26.85

24.10 24.70 24.10 24.70 24.70 28.10

18 44 23 11 1 23 44 34 18 17 33 27 38 28 26 11 37

16 32 19 9 1 18 23 20 11 11 22 19 27 19 18 7 22

14.40 13.60 13.30 Not enough taxa Not enough taxa 13.30 13.30 15.30 Not enough taxa 13.30 Not enough taxa 13.30 15.20 13.30 13.30 Not enough taxa 13.30

15.45 15.05 14.90

16.50 16.50 16.50

2.90 1.80 − 0.10

3.85 3.30 2.35

4.80 4.80 4.80

25.60 24.00 21.70

26.65 24.35 23.20

27.70 24.70 24.70

14.45 15.10 15.95

15.60 16.90 16.60

− 0.10 − 0.10 2.70

8.45 2.85 4.45

5.00 5.80 6.20

23.00 25.60 24.00

24.90 26.75 26.05

26.80 27.90 28.10

15.15

17.00

− 0.10

3.05

6.20

25.60

26.30

27.00

15.10 18.00 14.95 15.10

16.90 20.80 16.60 16.90

− 0.10 6.60 − 0.10 − 0.10

2.85 9.95 2.85 2.85

5.80 13.30 5.80 5.80

24.00 25.40 25.60 24.00

25.50 26.65 26.75 25.85

27.00 27.90 27.90 27.70

14.45

15.60

− 0.10

2.35

4.80

25.60

26.15

26.70

Ashutas Ashutas Ashutas Ashutas Berdy Chiliktysor Erzhilansay Kinjak Kinjak Kinjak Kinjak Kintykche Kintykche Krugloye Mynsualmas Mynsualmas Nausha b Locality name

Sample name

l.b.

Akmola AltynShokysu AltynShokysu AltynShokysu Ashutas Ashutas

Akmola 1 AltynShokysu II AltynShokysu IV AltynShokysu VI Ashutas-I Bol'shoj Log Ovrag I Ovrag II Ovrag III Ovrag V Pozadi Ovrag II

897 897

Ashutas Ashutas Ashutas Ashutas Ashutas

r.b.

l.b.

HMP [mm]

r.b.

l.b.

LMP [mm]

r.b.

l.b.

WMP [mm]

r.b.

962.5 962.5

1028 1028

109 109

139.5 139.5

170 170

43 43

43.5 43.5

44 44

49 84

66.0 130.5

83 177

897

962.5

1028

109

139.5

170

43

43.5

44

84

130.5

177

897

962.5

1028

109

139.5

170

43

43.5

44

84

130.5

177

897 897

962.5 962.5

1028 1028

122 115

128 124.5

134 134

43 43

43.5 43.5

44 44

92 68

92.5 80.5

93 93

962.5 962.5 935.5 1089.0

1028 1028 1028 1281

109 109 98 109

121.5 121.5 116 139.5

134 134 134 170

43 43 41 43

43.5 43.5 42.5 46.5

44 44 44 50

64 92 64 72

79.0 93.0 73.5 122.0

94 94 83 172

897 897 843 897 Not enough taxa

MAP [mm]

A.A. Bruch, S.G. Zhilin / Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32–48

45

Table 3 (continued ) Locality name

Sample name

Left border

MAP [mm]

Right border

Left b.

HMP [mm]

Right Left LMP b. b. [mm]

Right b.

Ashutas Ashutas Ashutas Ashutas Berdy Chiliktysor

Sloj-1 Sloj-2 Sloj-3 Sloj-4 Berdy ChiliktysorII–IV Erzhilansay 1 Kinjak 1a Kinjak 1b Kinjak 2a Kinjak 2b Kintykche 1a Kintykche 1b Krugloye-all Mynsualmas 1 Mynsualmas 2 Nausha 1

1122 897 897 Not enough taxa Not enough taxa 897

1179.5 962.5 962.5

1237 1028 1028

122 109 109

128 121.5 121.5

134 134 134

42 43 42

50.5 43.5 43.0

962.5

1028

109

124.5

140

42

962.5

1028

109

139.5

170

Erzhilansay Kinjak Kinjak Kinjak Kinjak Kintykche Kintykche Krugloye Mynsualmas Mynsualmas Nausha

897

Left b.

WMP [mm]

Right b.

59 44 44

84 92 72

89.0 92.5 83.0

94 93 94

43.0

44

84

102.0

120

43

43.0

43

108

140.0

172

897 Not enough taxa 897 Not enough taxa 897

1109.5

1322

124

147

170

9

26.0

43

73

131.0

189

1089.0

1281

109

139.5

170

43

46.5

50

84

113.5

143

962.5

1028

109

139.5

170

43

43.5

44

84

85.0

86

1183

1232.0

1281

115

175.5

236

19

31.0

43

85

128.5

172

897 897

962.5 962.5

1028 1028

109 109

139.5 127.5

170 146

42 43

43.0 43.0

44 43

55 92

116.0 100.5

177 109

1067.0

1237

109

121.5

134

43

49.0

55

93.0

94

Not enough taxa 897

and are visualised in Fig. 3. With the exception of the flora from Kintykche 1b, all other floras provide very similar results especially for mean annual temperature and precipitation. These values concentrate generally around 15 °C for MAT and 1000 mm for MAP, and reflect very equable climatic conditions across several thousands of square kilometres. However, other temperature parameters show minor spatial differentiation: the north-eastern part of the study area tends to be generally cooler and with slightly warmer summers and cooler winters. Accordingly, the annual ranges of temperature (MART) are higher in this area revealing a higher seasonality of temperature. For the easternmost locality Ashutas in Eastern Kazakhstan, however, it is notable that here the results document the lowest ranges of seasonal fluctuation in temperature due to relatively lower WMT and higher CMT values. Besides the equable MAP, other parameters of precipitation depict no spatial differentiation. With values for precipitation of the wettest month (HMP) around 140 mm, of the driest month (LMP) around 40 mm, and of the warmest month (WMP) exceeding 100 mm, it can be assumed that the main season of rainfall has been during or close to summer. The flora of Kintykche 1b gives warmer temperature values and higher precipitation results than all the other fossil floras. This can be explained by the fact that Kintykche represents one of the most western localities

92

of Turgayan floras (the Ustjurtian floras), which typically have some “western” species in common with contemporary European floras (Zhilin, 2004b). However, Kintykche 1b is a pollen flora, and therefore the determination of Nearest Living Relatives is mainly restricted to genus or family level. This reduces the value of its climatic interpretation as compared to the well determined leaf assemblages. The other two pollen floras give very wide and insignificant results due to the low taxonomic level of determination and are not even taken into account for quantitative investigations. 6. Discussion The Turgayan flora is a temperate flora that originated in Asia during the middle of the Cenozoic. In the Aquitanian the geographical distribution of the Turgayan flora was somewhat wider than the political borders of Kazakhstan today. This flora also occured in Bashkiria (Bashkortostan Republic, Russia), in the southern part of Western Siberia, and in the north-western part of Karakalpakia (Uzbekistan). In the western and central parts of Kazakhstan the Turgayan flora is very well dated: On the north-western part of the Ustjurt Plateau and in the region north of Lake Aral fossil remains of plants (mainly imprints of leaves) are dated by marine molluscs, shark teeth, ostrakods, and foraminifera; on the Turgay Lowland the Turgayan flora is well dated by

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A.A. Bruch, S.G. Zhilin / Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32–48

remains of mammals. However, in eastern Kazakhstan the palaeofloras of the Ashutas Mountain belong to the Oshagandy Suite and their age is established as Aquitanian by comparison to the flora of Erzhilansay on the Turgay Lowland and by correlation with palaeofloras from the marine Baygubek Suite (or Baygubek horizon) on the Ustjurt Plateau (Zhilin, 1974, 1984, 1989). The quantitative climate analyses pointed out that those taxa that are used for defining the stratigraphy in sites which are not dated independently (the index fossil species after Zhilin, 1989) are not the climatically relevant ones (cf. Table 2). This proves that despite possible stratigraphic uncertainties, the climatic analyses of the floras obtained results which are not influenced by the beforehand floristic or stratigraphic interpretation. Our data draw the picture of a very equable, temperate, humid climate in Kazakhstan during the Aquitanian. The generally low spatial differentiation of temperature and precipitation differ significantly from the Recent climatic situation, which is characterised by very low precipitation and extreme spatial and seasonal changes of temperatures. In Aquitanian these extreme continental climatic conditions have not yet been established due to the generally warmer, more equable global climate of the Miocene (e.g., Bruch et al., 2004, 2006). Moreover, the palaeogeographic position of the study area of course had influence on the climatic situation. During the Aquitanian the region of Kazakhstan was close to the Turan Sea (eastern part of Eastern Paratethys), which retreated during the Aquitanian from the Pre-Aralian Lowland towards southwest (Popov et al., 2004a,b). This shallow water body together with vast freshwater lakes on the Turgay Lowland should have caused a significant climatic buffing effect. A similar effect is described from the Late Miocene Pannonian Lake by Bruch et al. (2006). For comparison with other regions, quantitative data from Aquitanian are scarce, hardly published, and most of the data available are based on European floras. The localities closest to those in Kazakhstan are situated in Ukraine (Syabryaj et al., in press). Here, floras from the Ukrainian Plain as well as from the Carpathian Basin have been analysed with the CA method. Both show very humid conditions with values for mean annual precipitation above 1100 mm. Characteristically, the flora from the Ukrainian Plain provides slightly cooler temperature values (MAT: 15.6–15.6 °C; CMT 2.3– 7.1 °C, WMT 25.3–26.3 °C) than the flora from the Carpathian Basin (MAT: 15.6–16.1 °C; CMT 6.6– 7.8 °C, WMT 25.4–25.6 °C), especially in winter temperature (Syabryaj et al., in press). Although the

mean annual temperature and precipitation are significantly higher on the Ukrainian Plain, these data are most similar to our data from Kazakhstan. Like in Kazakhstan, also on the Ukrainian Plain the mean annual range of temperature is higher than in all localities further west. All other information available from European records shows warmer and especially more equable conditions with low seasonality. From Central Europe, data of Aquitanian floras from Hungary are published by Erdei et al. (in press), yielding a MAT of 15.6– 18.8 °C, CMT of 5–10.2 °C, and WMT of 25.6– 27.5 °C. Further south, data from Turkey (Akgün et al., in press) provide even warmer values of MAT 16.5– 21.3 °C, CMT 5.5–13.3 °C, and WMT 27.3–28.3 °C. Thus, all data available from European floras give much warmer mean annual temperatures (all N 15.6 °C), generally warmer winter temperatures, a lower seasonality of temperature, and slightly higher precipitation as compared to the results from Kazakhstan. All these data provide evidence for less continental influence on the climatic conditions in Europe compared to Central Eurasia. During the Early Miocene continentality increased from the Eastern European Platform towards the Turgay Lowland. For China and East Asia in general there are no published data available yet. The results of one analysis of a pollen flora from Bohai (east coast of North China, Lower Guantao Formation, early Early Miocene) are kindly provided by Liang (unpublished data): MAT 15.6–18.4 °C, CMT 5–12.5 °C, WMT 24.7–27.9 °C, and MAP 1122–1520 mm. These data match exactly what is known from Europe. Although we cannot draw any conclusion about the palaeoclimatic situation in China from one data point, we may state that all data in the central part of the Eurasian continent show evident signals of higher seasonality and of stronger continental influence than any from the western and eastern regions at the same time interval. Still, the Aquitanian climate in Kazakhstan differs profoundly from the modern situation with strong continentality by showing humid, temperate conditions with a much lower seasonal and spatial differentiation than today. Nevertheless, largescale regional differences in the Eurasian Aquitanian climate data give evidence of evolving continental climatic conditions in Central Eurasia that may have influenced the evolution of the Turgayan Flora. Non-palaeobotanical information about the general climatic situation in Eurasia during the Miocene is available from mammal hypsodonty (e.g., Fortelius et al., 2002, 2003). These data prove that during the Early Miocene Eurasia was dominated by brachydont faunas except for Central Asia and the Iberian Peninsula. The

A.A. Bruch, S.G. Zhilin / Palaeogeography, Palaeoclimatology, Palaeoecology 248 (2007) 32–48

higher number of mammals with increased crown height due to changes in food supply is interpreted as a signal of higher aridity in these areas. However, our data suggest that the climatic differences between Europe and Central Eurasia are mainly in temperature and seasonality of temperature and not in precipitation. It might be taken into account that changes in vegetation due to an increasing continental climate with a stronger differentiation of summer and winter temperatures may have influenced changes in vegetation and mammal hypsodonty in addition to rainfall. Still, the genuine causes of the development of the Turgayan Flora can only be addressed in future investigations on older floras of Kazakhstan. As stated by Zhilin (1989), the main replacement of the subtropical with temperate elements in Kazakhstan took place during the Late Eocene and Oligocene. Thus, a comparison of the results of this study with future analyses of those earlier floras and in comparison with contemporary data from other parts of Eurasia may bring light to the question if the rise of the Turgayan Flora was due to climate change. Acknowledgements The authors would like to express their thanks to Dr. Liang MingMei (Birmingham, UK) for providing unpublished data for comparison. Also the helpful comments of two anonymous reviewers are gratefully acknowledged. The present study was supported by RFBR (Russian Foundation for Basic Research) grant 03-04-49705 (Scientific leader S.G. Zhilin) and by BMBF grant RUS 02/118. This work is a contribution to the program ”Neogene Climate Evolution in Eurasia — NECLIME”. References Akgün, F., Kayseri, M.S., Akkiraz, M.S., in press. Palaeoclimatic evolution and vegetational changes during the Late OligoceneMiocene period in the Western and Central Anatolia (Turkey). In: Bruch, A.A., Uhl, D., Mosbrugger, V. (Eds.), Miocene Climate in Europe- Patterns and Evolution. Special volume of Palaeogeography, Palaeoclimatology, Palaeoecology. Andrejev, A.G., 1991. Floristicheskije svyazi pozdneoligotsenovoy i rannemiotsenovoi flor Altyn-Shokysu (Severo-Vostochnoe Priaral'e). Floristic relationships of the Late Oligocene and the Early Miocene floras of Altyn-Shokysu (North-Eastern Priaral'e). In: Zhilin, S.G. (Ed.), Development of the Flora in Kazakhstan and Russian Plain from the Eocene to the Miocene. Kryshofovich Lecture Series, vol. 2. Leningrad, pp. 98–127 (in Russian). Bruch, A.A., Utescher, T., Alcalde Olivares, C., Dolakova, N., Ivanov, D., Mosbrugger, V., 2004. Middle and Late Miocene spatial temperature patterns and gradients in Europe — preliminary results based on palaeobotanical climate reconstructions. Courier - Forschungsinstitut Senckenberg 249, 15–27.

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Zhilin, S.G., 1974. Tretichnye flory Ustyurta. The Tertiary floras of the Plateau Ustjurt (Transcaspia). Komarov Botanical Institute of the Academy of Sciences of the USSR. Leningrad. (in Russian). Zhilin, S.G., 1984. Osnovnye etapy formirovaniya umerennoi lesnoi flory v oligocene-rannem miocene Kazakhstana. Main stages of the development of the temperate forest flora in the OligoceneEarly Miocene of the Kazakhstan. Komarov Lecture Series, vol. 33. Leningrad, pp. 1–112 (in Russian). Zhilin, S.G., 1985. Etalonnye paleoflory i ikh rol' v raschleneniii korrelyatsii kontinental'nyh otlozhenij. The standard floras and their importance in the correlation of the continental deposition. Tezisy dokladov 31 sessii Vsesoyuznogo paleontologicheskogo obshchestva “Stanovlenie i evolyutsiya kontinental'nyh biot”. (Abstracts of the 31th Session of the All-Union Palaeontological Society “Rise and evolution of the continental biotas”). Leningrad, pp. 23–24 (in Russian). Zhilin, S.G., 1989. History of the Development of the Temperate forest Flora in Kazakhstan, U.S.S.R. from the Oligocene to the Early Miocene. The Botanical Review 55 (4), 205–330. Zhilin, S.G., 1991. Metodicheskie problemy paleofloristiki (na primere kazakhstanskih paleogenovyh i neogenovyh flor). Methods and problems of palaeofloristics (on the material of the Paleogene and the Neogene floras of Kazakhstan). In: Zhilin, S.G. (Ed.), Development of the Flora in Kazakhstan and Russian Plain from the Eocene to the Miocene. Kryshtofovich Lecture Series, vol. 2. Leningrad, pp. 98–127 (in Russian with English summary). Zhilin, S.G., 2002. Structure of the Turgayan flora in the Oligocene and Miocene and its palaeoclimatic features. Acta Palaeobotanica 41 (2), 141–146. Zhilin, S.G., 2004a. A.N. Kryshtofovich – shagi k poznaniyu fenomena turgaiskoi flory. A. N. Kryshtofovich – steps towards the recognition of the phenomenon of Turgayan flora. Abstracts of the Kryshtofovich Lecture Series, vol. 5. Russian Academy of Sciences, Komarov Botanical Institute, St. Petersburg, pp. 28–34 (in Russian). Zhilin, S.G., 2004b. O zapadnom forposte Turgaiskoi flory v Bashkirii (pozdnii oligocen-rannii miocen). On western outpost of Turgayan flora in Bashkiria (Late Oligocene-Early Miocene). Abstracts of the Kryshtofovich Lecture Series, vol. 5. Russian Academy of Sciences, Komarov Botanical Institute, St. Petersburg, pp. 34–36 (in Russian). Zhilin, S.G., 2005. O raznoobrazii kazakhstanskih flor v kontse pozdnego eozena. On the diversity of the floras emerged by the end of the Late Eocene in Kazakhstan [in Russian with English summary]. Modern Problems of Palaeofloristics, Palaeophytogeography and Phytostratigraphy. Transaction of the International Palaeobotanical Conference. Moscow, May, 17–18, 2005, vol. 1. USSR Academy of Sciences Publishing House, Moscow, pp. 97–101. Zhilin, S.G., Samsonov, N.I., 1999. Nekotorye paleobotanicheskie i paleogidrologicheskie dannye ob izmeneniyah sredy ozera Kruglogo (North–West Kazakhstan) v rannem miotsene (akvitane). Some palaeobotanical and palaeohydrological data on the changes of the environment of Krugloye Lake (North–West Kazakhstan) in the Early Miocene (Aquitanian). Toporkov Lecture Series, vol. 4. Rudnyi, Republik of Kazakhstan, pp. 466–472 (in Russian).