Early Miocene palaeoflora and palaeoecology of the Soma Basin, Western Turkey

ORIGINAL PAPER

Early Miocene palaeoflora and palaeoecology of the Soma Basin,

Western Turkey

Mehmet Serkan Akkiraz1 &Torsten Utescher2&Angela A. Bruch3 &Volker Wilde3&Sariye Duygu Durak1 & Volker Mosbrugger3

Received: 13 November 2019 / Revised: 27 February 2020 / Accepted: 29 April 2020

# Senckenberg Gesellschaft für Naturforschung and Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract

In this study comprehensive palaeofloristic data of lower Miocene deposits from the Soma Basin, western Anatolia is presented considering the stratigraphical concept. The sediments of the basin, derived from outcrop sections, were deposited in the terrestrial environment. The basin includes three different successions: lower and middle lignite successions of the Soma Formation and upper lignite succession of the Deniş Formation. In this paper, we address the early Miocene palaeoecology via pollen and leaf assemblages from the Soma Basin, dated precisely using radiometric data. High percentages of Cupressaceae in the lower lignite succession of the Soma Formation, and minor quantities of elements such as Carya, Nyssa, Myrica, Ulmus and Salix reflect a local riparian and swamp vegetation. Marls overlying the lower lignite succession represent an environment close to the source area, with a variety of flora. During the deposition of middle lignite succession wet conditions played an essential role in the swamp forest fostering some distance transport of pollen which reflect the mesophytic forest vegetation as well as higher altitudes in the hinterland. The high percentages of lacustrine plankton Botryococcus and presence of Spirogyra in the upper lignite succession of the Deniş Formation imply a shallow water environment with less rainfall surrounded by evergreen and deciduous mixed forest.

Keywords Miocene . Western Turkey . Soma Basin . Palaeoenvironment . Palaeoclimate

Introduction

Western Anatolia is part of the Aegean Province, which is a region of extensional deformation driven by the compli-cated convergence of the African and Eurasian plates. In response to crustal extension, southwest Anatolia is dom-inated by numerous graben structures that are mostly filled with Miocene to Recent continental clastic rocks including volcanic material and some carbonates (e.g. Şengör and Yılmaz 1981; Seyitoğlu and Scott 1994; Seyitoğlu 1997; Görür and Tüysüz 2001; Gürer and Yılmaz 2002; Purvis and Robertson 2005). Relevant

basins are either ~E–W-oriented or ~ N–S-oriented which is usually referred to as cross-grabens of Şengör (1987). During the early–middle Miocene lignite-bearing volcano-clastic deposits were accumulated in NE–SW trending ba-sins such as Kütahya (Seyitömer and Tunçbilek subba-s i n subba-s ) , Ç a n (Ç a n a kk a l e ) , S o m a (M a ni subba-s a ) , G ö r de subba-s (Manisa), İlyaslı (Uşak), Demirci (Manisa) and Selendi (Manisa). There are already many geological studies existing regarding their sedimentology, geochemistry and economic coal potential of the aforementioned basins (e.g. Nebert1978; Akgün et al.1986; Akgün and Akyol1987; Gemici et al. 1991; Akgün 1993; Seyitoğlu and Scott 1991; Takahashi and Jux 1991; Karayiğit and Whateley

1997; Karayiğit et al. 2000; İnci 1998, 2002; İnaner and Nakoman2004; Yağmurlu et al.2004; Akgün et al.2007; Akkiraz et al. 2011, 2015; Ersoy et al. 2012, 2014; Karayiğit et al. 2017). Moreover, a first palynological framework for these lignite-bearing sequences was established by the studies of e.g. Akgün et al. (1986), Gemici et al. (1991), Ediger (1990), Takahashi and Jux (1991) and Akgün (1993). Vegetation and quantitative palaeoclimate reconstructions for the basins were

* Mehmet Serkan Akkiraz sakkiraz73@gmail.com

1 _{Department of Geological Engineering, Kütahya Dumlupınar}

University, 43100 Kütahya, Turkey 2

Institut für Geologie, Nussalle 8, 53115 Bonn, Germany

3 _{Senckenberg Research Institute and Natural Museum,}

Senckenberganlage 25, 60325 Frankfurt am Main, Germany https://doi.org/10.1007/s12549-020-00434-3

summarized by Akgün et al. (2007) and Akkiraz et al. (2011) on the basis of sporomorph associations and pub-lished leaf floras. In this study, we extend the knowledge on floral (pollen and leaf) data by analyzing new samples from the overall lignite succession (lower, middle, and upper) of the Soma Basin. The purpose of this paper is to improve the understanding of the palaeoecology of the Soma and Deniş formations using pollen and leaf floras, especially by applying the Coexistence Approach (Mosbrugger and Utescher 1997) for quantitative palaeoclimate estimations.

Study area

The Soma Basin (39° 06′ 20″ N, 27° 35′ 03″ E and 550 m alt.) is located in the western part of Turkey (Fig.1a, b). In the area, Neogene deposits are considered to have been formed mainly in NE–SW trending karstic and possibly fault-bounded topo-graphic depressions, synclinal troughs, and in small intramontane settings (Takahashi and Jux1991;İnci1998,

2002). The basement rocks are Upper Cretaceous to lower Palaeocene turbidites, olistostromes/megabreccias, and ophiolite-related clastics (Figs.2 and3a). Miocene deposits unconformably overlie the basement and are composed of coarse to fine-grained clastic sediments including marls, lime-stones, volcanic and volcano-clastic rocks (Fig.3a). The basin fill belongs to two depositional cycles which were distin-guished from base to top as Soma and Deniş formations (Nebert1978). Coal-bearing sequences include the lower and middle lignite seams of the Soma Formation and the upper lignite seam of the Deniş Formation (Fig.3a). Coal mining focuses on the lower lignite seam which has up to 20 m thick-ness in total (Fig.3a, b). According toİnci (2002), the lower lignite succession was deposited in an alluvial fan of a lacus-trine system. The marl dominated lithologies including rich leaf assemblage rest on the lower lignite succession. The cal-careous freshwater deposits overlying the middle lignite suc-cession are deposits of an anastomosing river system (İnci

1998). The upper lignite succession containing volcano-clastics includes fluvial channel, floodplain and peat mire de-posits (İnci1998,2002). The age of the basin is still a matter of debate. In a first study, Nebert (1978) suggested a late Miocene age for the Soma Formation and an early Pliocene age for the Deniş Formation. Succeeding surveys claim a mid-dle Miocene age for both formations, according to palaeobotanical evidence (Akgün et al. 1986; Gemici et al.

1991; Akgün1993). Kaya et al. (2007) studied the stratigra-phy of the Zeytindağ and Bozalan areas, which are located at the southwestern side of the Soma Basin, and suggested a late early Miocene age (MN3-MN4; mid to late Burdigalian) for both formations, based on mammals such as Cricetodon kasapligili, Eumyarion cf. intercentralis, Aliveria sp.,

Democricetodon sp., Galerix, sp., Enginia sp., Sayimys sp., Gliridae and Lagomorpha. Moreover, Ersoy et al. (2014) suggested, on the basis of (40Ar/39Ar) from volca-nic rocks overlying the coal-bearing units (Soma and Deniş formations), that the Soma Basin may be developed d u r i n g t h e e a r l y M i o c e n e ( p r o b a b l y b e f o r e t h e Burdigalian). Hence, mammal and radiometric data to-gether make an early Miocene age highly probable for the development of the basin, while it still remains un-clear whether it evolved in the Aquitanian or Burdigalian.

Material and methods

A total of three sections from the open cast mines (called Işıklar and Deniş) were partly measured and palynologically sampled (Fig.3b–d), two of them from the lower and middle lignite successions of the Soma Formation northeast of Soma (Figs.2 and 3b, c), and another one from the upper lignite succession of the Deniş Formation to the southwest of Soma (Figs.2and3d).

A total of 63 palynological samples has been collected from fine-grained sediments and lignites (Fig. 3). The distribution of the samples is categorized as follows: 9 samples were taken from the lower lignite succession (Fig. 3b), 47 samples from the middle lignite succession (Fig. 3c), and 7 samples from upper lignite succession (Fig. 3d). Samples having less than 100 pollen grains were not included in the analyses. Quantitative data are thus confined to 41 samples, of which 5 of 7 came from the lower (Fig. 4a), 29 of 47 samples from the middle (Fig.4b) and 7 samples from the upper lignite successions (Fig. 5).

For the recovery of palynomorphs, mineral components were first removed from the samples by the use of acids: silicates were removed by 40–60% HF, carbonates (com-monly found as calcite) were dissolved in HCl, sulphates, sulphides and excess carbonaceous (“bituminous”) mate-rial is soluble in concentrated HNO3. Finally, slides were

prepared from the productive samples for qualitative and quantitative assessment of palynomorphs. The individual grains were assigned to genera and families as far as pos-sible, selected examples are illustrated on Fig. 8. In most cases, the spore and pollen sums are based on more than 200 grains. TILIA software was used to calculate the palynomorph percentages, and TILIGRAPH was used to plot the diagrams (Grimm 1994). All pollen slides are h o u s e d a t t h e K ü t a h y a D u m l u pınar University, Department of Geological Engineering.

The Coexistence Approach (CoA) has been used to calculate palaeoclimate estimates (Mosbrugger and Utescher 1997; Utescher et al. 2014). Application of the CoA is facilitated by the program ClimStat and the

İİzmir Aliağa Bergama Edremit Manisa Turgutlu Gölmarmara Salihli Alaşehir Ödemiş Tire Kula Simav Balıkesir Ezine ANTALYA ANKARA ESKİŞEHİR KIRIKKALE TOKAT SİVAS ÇORUM ADANA MARDİN İSTANBUL BLACK SEA A E S N A E G E A MEDITERRANEAN SEA GEORGIA GREECE SYRIA IRAQ ARME. IRAN MACE. SERBIA ROMANIA RUSSIA BULGARIA area in fig.1b N W E S 0 80 160km

AEGEAN

SE

A

38 00 00

39 00 00

27 00 00

28 00 00

29 00 00

a

b

b

database Palaeoflora that includes nearest living relatives (NLRs) of more than 10,000 Cenozoic plant taxa, together with climatic requirements, which are derived from mete-orological stations, located within the distribution areas of the taxa (see also information given on the web sitewww.

palaeoflora.de). The CoA was applied to all palynological

samples as well as to the macroflora. The following climate parameters were considered: MAT–mean annual temperature (°C); CMT–mean temperature of the coldest month (°C); WMT–mean temperature of the warmest month (°C); MAP–mean annual precipitation (mm); HMP–precipitation of the wettest month (mm); LMP–

Tavşanlı

Savaştape

BALIKESİR

Soma

Bakırçay

Kınık

Kırkağaç

Bakır

Gelenbe

27 38'

39 20'

39 30'

0 1 2 3 4km

Basement

lower and middle

coal successions

upper coal

succession

volcanic rocks

Plio-Quaternary

deposits

basalt extrusions

Soma Fm.

Deniş Fm.

N

W

E

S

MESOZOIC Basaltic extrusion LOWER MIOCENE QUA TERNAR Y Nebert, 1978 Limestone, sandstone and conglomerate Green claystone Silicified limestone Marls Volcaniclastic apron and alluvial plain deposits

Green fine - grained sandstone dominated alluvial -lacustrine deposits DENİŞ FORMA TION Limestone Lignite with gastropod

Marls with fossil leaves

Sandstone, mudstone with gastropod

Conglomerate

SOMA

FORMA

TION

Clastic and carbonate rocks

of İzmir - Ankara zone Basement

m1 k1 m2 k2 m3 k3 p1 p1 p2 p3 p2

Lignite with gastropod

Investigated sediments b c d (a) 20 50 55 Lithology m (c) 25 5 LOWER MIOCENE SOMA 35 40 45 30 Fm. Age 07/231 07/232 07/233 07/269 07/234 07/235 07/236 07/237 07/238 07/239 07/24007/241 07/242 07/243 07/244 07/245 07/24607/247 07/248 07/249 07/250 07/251 07/25207/253 07/254 07/255 07/256 07/257 07/258 07/260 07/261 07/262 07/264 07/263 07/265 07/266 07/267 07/268 07/270 07/271 07/272 07/273 07/274 07/275 07/276 07/277 07/259 py,fe s s s s s 15 0 s not to scale 07/368 07/369 07/370 07/371 07/372 07/373 07/374 07/375 07/376 5 10 m Fm. Age SOMA LOWER MIOCENE Lithology (b) 0 15 10 5 45 40 55 60 50 Fm . Age Lithology m (d) 35 30 25 LOWER MIOCENE DENİŞ 07/406 07/407 07/411 07/412 07/409 07/410 07/408 fe 0 15 20 lignite claystone sandstone limestone marl tuffite conglomerate petrified wood plant debris algal mound gastropod py pyrite fe ferruginous s sulfurous bioclast 10

Fig. 3 a Generalized columnar section of the Soma Basin. b Measured section from the lower lignite succession of the Soma Formation. c Measured section

p r e c i p i t a t i o n o f t h e d r i e s t m o n t h ( m m ) ; W M P– precipitation of the warmest month (mm).

Palynological data

Quantitative palynological data from the lower, middle and upper lignite successions are presented separately (Figs.4and5). Lower lignite succession (lower part of the Soma Formation) This microflora includes 29 palynomorph taxa, consisting of angiosperms (68%), gymnosperms (16%), and pteridophytes (16%) (Fig.4a). Angiosperms are represented by 18 taxa that may be assigned to 15 families. Gymnosperms comprise 4 taxa belonging to 3 families. Cosmopolitan Cupressaceae and other conifers are common throughout the section. Evergreen and deciduous mixed forest elements such as

Castanea-Castanopsis, Engelhardia and Arecaceae are pres-ent at relatively low quantities. Also, there is a poor associa-tion of pteridophytic spores such as those of Lycopodium, Monoleiotriletes minimus, Osmunda, Selaginellaceae and Polypodiaceae-Thelypteridaceae with the abundance of indi-vidual taxa varying considerably from one sample to the other (Fig.4a) Based on quantitative changes of the relative abun-dances of the palynomorph assemblages, two local pollen zones are distinguished (Fig.4a).

Local pollen zone SM-I (0–7.65 m; samples 07/368–372 from the lower part of the Soma Formation)

This zone is distinguished by the highest average content of Quercus as represented by values from 5 % to 12 %, with a maximum of 13.8 % at 6.15 m, and Polypodiaceae-Thelypteridaceae represented by values from 4 % to 5 %, with a maximum 9.2 % at 6.15 m (Fig. 4a). The latter

a

b

lower lignite succession

0,2 0,4 0,6 Total sum of squares

CONISS 07/376 07/375 07/373 07/372 07/368 Polypodiaceae-Thely .

Monoleiotriletes minimus Osmunda Selaginellaceae Lycopodium undif

ferentiated Pin.

Picea Pinus diploxylon

type

Pinus haploxylon

type

Cathaya

20 40 60 80 Cupressaceae Castanea-Castano. Engelhardia Arecaceae Sapotaceae Rhus

20

Quercus Corylus Carpinus Betula Cycas Carya Ulmus Salix Nyssa Myrica Sparganium Poaceae Caryophyllaceae

20

spores

20 40 60 80

coniferous forest

20 evergreen and deciduous mixed forest riparian vegetation aquatics herbs spores coniferous forest evergreen and

deciduous mixed forest riparian forest swamp forest aquatics herbs m _{Pollen zones} 07/277 07/276 07/275 07/274 07/273 07/271 07/270 07/269 07/268 07/267 07/266 07/265 07/264 07/263 07/262 07/261 07/260 07/259 07/258 07/255 07/253 07/252 07/247 07/244 07/242 07/238 07/237 07/234 07/231 10 20 30 40 50 0 40 60 spore sum 120 160 200 pollen sum grains Soma Formation

middle lignite succession

m Polypodiaceae: Microlepia Pteridaceae: Pteris 2040 Polypodiaceae-Thelypteridaceae Dennstaedtiaceae: Paesia

Picea Podocarpus Pinus haploxylon

type

Pinus diploxylon type undif

ferentiated Pinaceae

Cathaya Cedrus Ts

u

g

a

Cupressaceae Arecaceae Cycas

20 60

Engelhardia Corylus Betula

s u ni pr a C 20 60

Quercus Rhus Trigonabalanus

20

Castanea-Castanopsis

20 Cyrillaceae-Clethraceae Araliaceae Mastixiaceae Oleaceae Liquidambar Sapotaceae Carya

20

Pterocarya Ulmus Zelkova

20 60

Alnus Salix Myrica Nyssa Ephedra Poaceae Chenopodiaceae-Amaranth.

20 Sparganium Ovoidites 2040 spores 20 coniferous forest 20 60

evergreen and deciduous mixed forest

20 60 riparian forest swamp forest herbs

20 aquatics algae

2 4 6 8 Total sum of squares

CONISS spores coniferous

forest evergreen and deciduous mixed forest riparian forest

swamp forest aquatics herbs algae SM-III SM-IV pollen zones percentages Magnoliaceae

Fig. 4 a Pollen diagram of the lower lignite succession of the Soma Formation. b Pollen diagram of the middle lignite succession of the Soma Formation

(Polypodiaceae-Thelypteridaceae) abundances tend to de-cr ea se thro ug h th e up per pa rt o f th e SM- I z on e. Cupressaceae occur abundantly and range from 40 to 50 %. Undifferentiated Pinaceae appear regularly with constant values of 2.5–9.8 % and Ulmus, Salix, Betula and Caryophyllaceae occur in low percentages.

Local pollen zone SM-II (7.65–15.00 m; samples 07/373–376 from the lower part of the Soma Formation)

Spores as Monoleiotriletes minimus, and those of Osmunda and Selaginellaceae, slightly increase in this zone (Fig.4a). The pollen of Cupressaceae have more or less similar values as in zone SM-I, peaking to 75 % at 15 m (sample 07/376). Abundances of Quercus decrease and range from 1.8 to 3.0 %. The abundances of Cycas slightly increase and reach up to 9.7 % at 7.35 m (sample 07/373) (Fig.4a). Pollen of Pinus haploxylon type, Picea, Carpinus, Carya, Nyssa and Poaceae, absent in zone SM-I, appear in minor quantities.

Middle lignite succession (upper part of the Soma Formation) The samples provide a total of 42 palynomorph taxa of pteri-dophytes, gymnosperms and angiosperms. Angiosperms dominate (70 %). Gymnosperms (19 %), pteridophytes (9 %) and algae (2 %) occur in less percentages. Angiosperms are represented by 28 taxa which are assigned to 21 families (Fig.4b). Gymnosperms include Picea, Podocarpus, Pinus haploxylon type, Pinus diploxylon type, Cathaya, Cedrus, Tsuga, undifferetiated Pinaceae, and Cupressaceae which show no clear trend in percentages along the section. Pteridophytes are represented by 4 spore taxa (Microlepia, Pteris, Paesia, and Polypodiaceae-Thelypteridaceae), which

can be assigned to 3 families and freshwater algae by minor quantities of Botryococcus (Fig.4b). The palynological as-semblages mainly include evergreen and deciduous mixed forest elements such as Engelhardia (2.5 to 60 %), Quercus (1.3 to 61.2 %), Castanea-Castanopsis (1.2 to 11.2 %), Cyrillaceae-Clethraceae (1.1 to 13.80 %), and riparian forest elements such as Alnus (1.2 to 58.3 %) and Pterocarya (1.2 to 24.8 %). Swamp, herbaceous and aquatic plants are represent-ed by minor quantities throughout the succession. The paly-nological assemblage can be divided into two pollen zones on the basis of their composition.

Local pollen zone SM-III (0–24.20 m; samples 07/231–258 from the upper part of the Soma Formation)

This zone is characterised by high quantities of evergreen and deciduous mixed forest taxa including Engelhardia (5.3 to 60.1 %), Quercus (9.8 to 61.2 %), Castanea-Castanopsis (2.1 to 11.2 %), and Cyrillaceae-Clethraceae (1.1 to 12.1 %). Undifferentiated Pinaceae, Cupressaceae, Cycas, and Myricaceae were recorded consistently (Fig.4b). In contrast, the pollen of Araliaceae, Carya and Carpinus occur irregular-ly. Pollen of Alnus shows an increase throughout zone SM-III. In the assemblage, riparian, coniferous forest and swamp for-est taxa are of secondary importance. The abundance of Pterocarya is constant, but minor in quantity.

Local pollen zone SM-IV (24.2–54.60 m; samples 07/259–279 from the upper part of the Soma Formation)

In this zone, percentages of evergreen and deciduous mixed forest taxa are lower than in zone SM-III, whereas abundances of riparian forest elements such as Pterocarya (4.8 to 24.6%) and Alnus (22.4 to 58.3 %) are high. The prominent feature of

0,4 0,8 1,2 Total sum of squares

CONISS

20 Polypodiaceae-Thelyp. Pteridaceae Schizaeaceae Pinus haploxylon

type Pinus diploxylon type Cathaya undif ferentiated Pinaceae 20 40 60 Cupressaceae Engelhardia 20 Castanea-Castanopsis 20

Clethraceae-Cyrillaceae Rhus Sapotaceae Fagaceae Carpinus Corylus Oleaceae Phyllirea Acer Juglandaceae Tilia

20

Sambucus Cycas

20

Alnus Ulmus Zelkova Carya

20

Salix Platanus Taxodium Myrica Sparganium Lemnaceae Potamogetonaceae Poaceae Liliaceae Chenopodiaceae-Amar

. Urtica Spirogyra 20 40 Botryococcus 20 20 40 60 20 40 60 20 20 40 swamp forest algae 20 40 Quercus 30 35 15 Deniş Formation upper li gnite succession 80 100 spore sum 300 pollen sum grains 07/412 07/411 07/410 07/409 07/408 07/407 07/406 m 13 spores coniferous

forest evergreen and deciduous mixed forest riparianforest

aquatics

herbs

spores coniferous forest evergreen and deciduous mixed forest

riparian forest swamp forest aquatics herbs algae

percentages

D-I

D-II

Pollen zones

Fig. 5 Pollen diagram of the upper lignite succession of the Deniş Formation (percentages of floral components in samples are indicate). See Fig.3dfor

this zone is a conspicuous decrease in quantities of Engelhardia (8 to 16.2 %) and Quercus (1.8 to 20.8 %). The amounts of Castanea-Castanopsis (1.1 to 9.8 %) and Cyrillaceae-Clethraceae (1.2 to 4.7 %) tend to decrease in this z o n e . I n p a r a l l e l p e r c e n t a g e s o f P o l y p o d i a c e a e -Thelypteridaceae (4.8 to 35.1 %), Alnus (24.4 to 55.2 %) and Pterocarya (5.3 to 21.3 %) persistently increase. Pollen of Cycas, Carpinus, Fagaceae and Oleaceae occur constantly, albeit minor in proportions.

Upper lignite succession (Deniş Formation)

The assemblages consist of 42 palynomorph taxa, including angiosperms (78 %), gymnosperms (11 %), pteridophytes (7 %) and freshwater algae (4 %). Angiosperms are repre-sented by 30 pollen taxa which are assigned to 24 families (Fig.5). Gymnosperms include 5 pollen taxa which can be assigned to 2 families. Three taxa of spores, such as Polyp odia cea e-Thely pter idac eae , Pter idac eae a nd Schizaeaceae, are recognised. The assemblages also in-clude high percentages of freshwater algae such as Botryococcus (32.2 to 47.8 %). Based on their composition two zones may be distinguished in the palynological assem-blages (Fig.5).

Local pollen zone D-I (0–26.25 m; samples 07/406–409 from the lower part of the Deniş Formation)

In this zone, percentages of evergreen and deciduous mixed forest taxa (40 to 60 %) and freshwater algae (30 to 40 %) are high (Fig.5). Lower percentages of coniferous forest (15 to 21.2 %) and riparian forest taxa (3.7 to 26.1 %) are recorded. Pollen of swamp forest, freshwater, and herbaceous plants occur in minor quantities. This zone is also distinguished by high percentages of Castanea-Castanopsis (1.1 to 15 %), Cyrillaceae-Clethraceae (0.2 to 16 %), Quercus (1.2 to 37.2 %). Undifferentiated Pinaceae (1.2 to 7.3 %) and Platanus (1.3 to 7.5 %) appear here with lower values.

Local pollen zone D-II (26.25–36.30 m; samples 07/410–412 from the middle part of the Deniş Formation)

Here, coniferous forest elements such as Cupressaceae (6.2 to 45 %) show an increase with a maximum of 60.1 % at 27.2 m (sample 07/410). But at the same time, evergreen and decid-uous mixed forest elements such as Quercus, Castanea-Castanopsis and Cyrillaceae-Clethraceae tend to decrease. Alnus shows a tendency to increase up to 10 % at 27.2 m (Fig.5). Pollen of Platanus occurs regularly with values from 1.1 to 7.8 %.

Leaf flora

Apart from palynomorphs, fossil leaves were analysed for palaeoenvironmental reconstruction. A large number of well-preserved leaves has previously been described from the marl dominated lithologies by Nebert (1978), Gemici et al. (1991), Akgün et al. (2007) and Erdei et al. (2010). In our study, the number of leaf taxa from the flora of the Soma Formation has even been augmented by newly determined taxa such as Cupressaceae and Mahonia (Table 1). Nebert (1978), Gemici et al. (1991) and the current study reported a total of 111 taxa (Fig.3aand Table1) from the marls above the lower lignite succession which may correspond to the lower part of local pollen zone SM-III of the middle lignite succession (Fig.3a). The assemblage is predominantly com-posed of Cinnamomum, Quercus, Apocynophyllum, Ficus, Glyptostrobus europaeus (Ett.) Heer Laurophyllum, Myrica, Nerium, Olea, Salix, and Robinia. Glyptostrobus europaeus, Myrica lignitum, Juncus, and Salix point to a swamp vegeta-tion along the lakeshore. Mixed mesophytic forest and conif-erous plants (Fagus, Quercus and Pinus) covered dry ground. A tropical to warm-temperate climate was suggested based on t h e p r e s e n c e o f C i n n a m o m u m s c h e u c h z e r i H e e r , Cinnamomum polymorphum Heer, Myrica lignitum (Ung.) Sap., Laurophyllum princeps (Heer) Kr. and Weyl., M a g n o l i a l u d w i g i E t t . , F i c u s s p . , N e r i u m s p . , Apocynophyllum sp. and Olea sp., and some temperate taxa, such as Ulmus carpinoides Goepp., Quercus cf. buchi Heer, Acer trilobatum (Stbg.) A.Br., Buxus sp., Salix varians Goepp., Tilia sp., Populus latior A.Br., Robinia sp., Cercis sp., Glyptostrobus europaeus (Ett.) Heer Pinus palaeostrobus (Ett.) Heer and Ceratonia emarginata Heer (Nebert 1978; Gemici et al.1991).

Palaeovegetation

Combining information from the fossil record of palynomorphs and leaves, it is possible to develop a comprehensive view of the different vegetation units around the Soma Basin. Vegetation cover was rather diverse and is mainly represented by coniferous forest taxa and evergreen deciduous mixed forest taxa. In the palynological record, there is no distinct floral change between the assemblages of the Soma and Deniş forma-tions. However, some differences in the frequency of distinct taxa are seen.

During the deposition of the lower lignite succession (Soma Formation) coniferous trees such as undifferentiated Pinaceae and Cupressaceae were widespread. The percentages of evergreen and deciduous mixed forest elements such as Castanea-Castanopsis, Engelhardia, Arecaceae, Quercus and Cycadaceae are low. Ferns and herbaceous taxa also

occur, albeit in minor amounts. The main swamp assemblage is characterised by Cupressaceae, Nyssa and Myricaceae. Low percentages of spores should be related to wet and swampy areas while the margins of the basin were colonized by Ulmus, Carya, Nyssa and Myricaceae. Salix thrived along the margins of lakes and river banks.

Marl dominated lithologies with well-preserved leaves oc-cur on top of the lower lignite succession. The leaves obtained reflect the local vegetation, i.e. the vegetation close to the lake system. Swamp habitats were composed of Glyptostrobus eurapaeus, Taxodium distichum, Myrica lignitum, M. pseudolignitum, Populus cf. balsamoides and Comptonia.

Table 1 Macrofloral list for the Soma Basin. Taxa highlighted in bold are responsible for the definition of climate intervals

(Nebert1978; Gemici et al.1991

and this study)

Acer sp. Magnolia sp.

Acer trilobatum (Stbg.) A.Br. Mahonia (?) aspera (Unger) Kovar-Eder and Kvacek Acer cf. decipens (A. Br.) Heer Mahonia sp.

Ailanthus sp. Morus cf. rubra L.

Alnus feroniae (Unger) Czecz. Myrica lignitum (Ung.) Sap. Apocynophyllum cf. helveticum Heer Myrica pseudolignitum Kr. and Weyl.

Apocynophyllum sp. Myrica sp.

Berberis sp. Nerium sp.

Betula sp. Olea sp.

Buxus sempervirens L. Persea cf. indica Spreng

Buxus sp. Pinus palaeostrobus (Ett.) Heer

cf. Carpinus miocenica Tan. Pinus cf. pinaster L. Carya cf. minor Sap. and Mar. Pinus cf. taeda L. Carya cf. serraefolia (Goepp.) Kr. Pinus sp.

Carya sp. Pistacia lentiscus L.

Castanea cf. sativa Mill. Planera sp.

Castanea atavia Ung. cf. Platanus aceroides Goepp.

Castanea sp. cf. Podogonium knorrii Heer

Ceratonia emarginata Heer Podogonium sp.

Ceratonia sp. Populus mutabilis Heer

Cercis sp. Populus latior A.Br.

Cinnamomum polymorphum Heer Populus cf. balsamoides Goepp.

Cinnamomum scheuchzeri Heer Populus sp.

Cinnamomum sp. Quercus ilex L.

Clematis cf. vitalba L. Quercus oligodonta Sap.

Colutea salteri Heer Quercus drymeja Ung.

Cornus sp. Quercus kubinyii (Kov.) Czec.

Corylites sp. Quercus mediterranea Unger

Corylus cf. avellana L. Quercus cf. buchi Heer

Cupressaceae Quercus cf. infectoria Ol.

Cycadaceae Quercus cf. neriifolia A.Br.

Dryophyllum sp. Quercus cf. trojana P. B. We.

Engelhardia Quercus sp.

Eotrigonobalanus furcinervis (Rossm.) Kr. and Weyl. Robinia regeli Heer

cf. Equisetum sp. Robinia sp.

Eucalyptus sp. Sagittaria cf. victor–masoni Ward.

Fagus ferruginea Ait. Salicites sp.

Fagus sp. Salix angusta Heer

Ficus lanceolata Heer Salix longa A.Br.

Ficus cf. archinervis Heer Salix varians Goepp.

Ficus cf. tiliaefolia Heer Salix sp.

Ficus sp. Sapindus cf. falcifolia A.Br.

cf. Frangula almus Mill. Sequoia langsdorfii (Br.) Heer Fraxinus excelsifolia Web. Sideroxylon salicites (Web) Weyl. Glyptostrobus europaeus (Ett.) Heer Sideroxylon sp.

Glyptostrobus sp. Taxodium distichum Rich.

cf. Illicium chenanum Kr. and Weyl. Taxodium dubium (Stbg.) Heer

Ilex sp. Taxodium sp.

Juglans acuminata A.Br. Tilia sp.

Juncus sp. cf. Thuja occidentalis L.

Laurophyllum primigenium (Ung.) Kr. and Weyl. Ulmus carpinoides Goepp. Laurophyllum princeps (Heer) Kr. and Weyl. cf. Ulmus longifolia Ung.

Laurophyllum sp. Ulmus sp.

Leguminosae Zelkova ungeri Kov.

Liquidambar sp. Ziziphus ziziphoides (Ung) Weyl.

Evergreen and deciduous mixed forest elements consist of Laurophyllum primegenium, Sapindus falcifolia, Carya serrafolia, Carya cf. minor, Tilia, Acer trilobatum, Acer cf. decipens, Ulmus, Zelkova, Castanea-Castanopsis, Fagus, Juglans, Magnolia, Betula and Daphnogene (species of Cinnamomum). Semi-xerophytic vegetation is represented by Leguminosae type and Cercis and characteristic Mediterranean xerophytes Quercus drymeja, Q.ilex, Q. kubinnyii, Q. mediterranea and Olea. Coniferous forests consisted of various species of Pinus. Sclerophyllous plants were composed of the representatives of the genera Pistacia, Ziziphus and Ceratonia.

During the deposition of the middle lignite succession, riparian forests and evergreen- deciduous mixed forests were common (Fig. 4b). The percentages of Alnus and Pterocarya, which are constituents of a wet environment, increase from the lower part to the top of the succession, whereas semi-evergreen Engelhardia and Quercus de-crease. Evergreen and deciduous mixed forest elements such as Cycas, Carpinus, Castanea-Castanopsis and Cyrillaceae-Clethraceae occur constantly. The understorey plant association consists of ferns such as Polypodiaceae/ Thelypteridaceae and Paesia. Coniferous plants refer to mid and higher altitudes and include high quantities of indeterminate Pinaceae and Pinus haploxylon type, and minor quantities of Picea, Cedrus, Tsuga, Podocarpus and Cathaya. However, it should be kept in mind that Pinus is not restricted to mid altitudes, but can partly even thrive swamps (Suc and Drivaliari 1991). High altitude trees are represented by pollen of cool-temperate taxa such as Picea and Cedrus. Because of higher precipita-tion, they may have been transported over longer dis-tances by rivers before reaching the basin. The swamp habitat is characterised by Cupressaceae that are common in the lower and upper lignite successions. However, only in the middle succession, they decrease while other taxa remain stable. This is conceivably related to subsidence of the basin, not to a vegetation change and a climate signal. Herbaceous plants and swamp elements occur in minor amounts.

During the deposition of the upper lignite succession (Deniş Formation), coniferous forests, evergreen to deciduous mixed forests, riparian vegetation and algae played a major role. The swamp environment was characterised by high quantities of Cupressaceae and minor percentages of Taxodium and Myricaceae. Algae such as Botryococcus and Spirogyra, which were lacking in the lower lignite succession and only represented in parts of the middle lignite succession, were abundantly recorded here. They indicate shallow water conditions probably related to a low amount of precipitation (Guy-Ohlson1992).

So, the dominance of Cupressaceae, riparian forest associ-ations and well-preserved leaves indicate that the source of the

plant fossils was not far from the area of deposition in the Soma Basin, which was enclosed by dense evergreen and deciduous mixed forest and coniferous forest associations de-pending on the altitude. Previous studies carried out in the lower- middle Miocene successions of western Turkey re-vealed similar pictures (e.g. Akgün and Akyol1987; Akgün and Akyol 1999; Akgün et al. 2007; Yavuz et al. 1995; Yavuz-Işık 2007; Kayseri and Akgün 2008; Yavuz-Işık

et al.2011; Emre et al.2011; Akkiraz 2011; Akkiraz et al.

2012,2015; Üçbaş-Durak and Akkiraz2016).

Palaeoclimate

Today the average elevation of the Soma area is about 550 m a.s.l. The area has hot, dry summers and mild rainy winters. The present climate of the area is MAT ~ 17 °C, CMT ~ 11 °C, WMT ~ 23 °C, MAP ~ 700 mm, HMP ~ 250 mm, LMP ~ 10 mm and WMP ~ 150 mm (Kadıoğlu2000; according to meteorological general management).

Taxa of the palynomorph assemblages have been assigned to ten synthesized climatic palynomorph groups according to Suc (1984), Jiménez-Moreno et al. (2005), Popescu (2006) and Ivanov et al. (2012). Proportions of mega-mesothermic; mesothermic; meso-microthermic, and microthermic elements; herbs; Mediterranean xerophytes; undifferentiated Pinaceae; Cupressaceae; Cathaya and freshwater algae are distinguished (Fig. 6). According to the assignment of the fossil palynomorphs to climatic (ecophysiologic) groups, in the low-er lignite succession (Soma Formation) the group of mega-mesothermic components, Engelhardia, Arecaceae, Sapotaceae, and Cupressaceae is overwhelmingly prominent (Fig. 4a). Some other mega-mesothermic elements such as Myrica occur in comparatively minor amounts. Cupressaceae

„

Fig. 6 Synthetic pollen diagram of the Soma Basin. Pollen taxa have

been grouped on the basis of ecological criteria (according to Suc1984,

Jiménez-Moreno et al.2005, Ivanov et al.2012).

- Mega-mesothermic elements (subtropical): Arecaceae, Engelhardia, Myrica, Sapotaceae, Castanea-Castanopsis, Araliaceae, Cyrillaceae-Clethraceae, Taxodium

- Cathaya

- Mesothermic elements (warm temperate): deciduous Quercus, Carya, Pterocarya,Oleaceae, Carpinus, Platanus, Zelkova, Ulmus, Tilia, Acer, Liquidambar, Caprifoliaceae, Alnus, Salix, Rhus, Nyssa, Betula, Sequoia and Fagus

- Meso-microthermic element (cool temperate): Cedrus, Tsuga - Microthermic element (cool): Picea

- Pinus, Podocarpus and indeterminate Pinaceae - Mediterranean xerophites: Phillyrea

- Cupressaceae

- Herbs–shrubs: Poaceae, Potamogeton, Liliaceae, Chenopodiaceae–

Amaranthaceae, Lilium, Urtica, Ephedra, Sparganium, and Caryophyllaceae

07/412 07/411 07/410 07/409 07/408 07/407 07/406 07/277 07/276 07/275 07/274 07/273 07/271 07/270 07/269 07/268 07/267 07/266 07/265 07/264 07/263 07/262 07/261 07/260 07/259 07/258 07/255 07/253 07/252 07/247 07/244 07/242 07/238 07/237 07/234 07/231 07/376 07/375 07/373 07/372 07/368 20 40 60 20 40 60 80 20 20 40 60 80 20 herbs 20 40 Deniş Formation Soma Formation

middle lignite succession

lower lignite succession

upper lignite succession

meso-microthermic elements (mid-altitude trees) microthermic el. (high-altitude trees) mega-mesothermic elements (subtropical)

mesothermic elements (warm temperate)

Cathaya Pinus , Podocarpus undif ferentiated Pinaceae

Cupressaceae mediterranean xerophytes freshwater algae

SM-I SM-II Pollen zones SM-III SM-IV D-I D-II

remain constant in both SM-I and SM-II zones. The mega-mesothermic elements Engelhardia, Arecaceae and Sapotaceae show only minor variation from zone SM-I to SM-II (Fig.4a). In contrast, the group of mesothermic, meso-microthermic and meso-microthermic components is less prominent (mid to high altitudinal trees). A slight increase in the abun-dances of mesothermic elements is reported in the upper part of the zone SM-I.

In the middle lignite succession (Soma Formation), the m a i n c o m p o n e n t s c o n s i s t o f m e g a - m e s o t h e r m i c (Engelhardia, Castanea-Castanopsis, Cyrillaceae-Clethraceae, Myrica) and mesothermic elements (Quercus, Carpinus, Alnus, Pterocarya etc.). However, there are some differences between zones SM-III and SM-IV. For instance, the mega-mesothermic element Engelhardia is common in the SM-III zone, but scarce in zone SM-IV (Fig. 4b). Similarly, the mesothermic element Quercus is represented by high percentages in zone SM-III, and decreases in zone SM-IV (Fig.4b). Compared to the lower lignite succession, pollen of Cupressaceae decrease strikingly in the middle

lignite succession (Soma Formation). This may have been linked to subsidence of the basin (i.e. uplift of mountains) as evidenced by an augmentation in meso-microthermic and microthermic elements such as Picea, Cedrus and Tsuga.

The upper lignite succession of the Deniş palynoflora in-cludes high quantities of mega-mesothermic elements, mesothermic elements, Cupressaceae and freshwater algae (Fig. 6). The mega-mesothermic elements Engelhardia, Castanea-Castanopsis and Cyrillaceae-Clethraceae occur constantly in zones D-I and D-II (Fig.5). However, zone D-I is rich in the mesothermic element Quercus which disap-pears in zone D-II. The freshwater alga Botryococcus is rep-resented by high percentages (exceeding 30 %) throughout zones D-I and D-II (Figs.5 and 6). Its augmentation here may be related to shallow water in combination with low precipitation.

The quantitative palaeoclimate data as derived from the application of the CoA to the palynofloras of the Soma Basin are shown in Fig.7. For the lower lignite succession (5 sam-ples), the coexistence intervals for all palaeoclimate parameters

07/368 07/372 07/373 07/375 07/376 5 10 15 20 25 30 5 10 15 20 25 30 07/231 07/234 07/237 07/238 07/242 15 20 25 07/244 0 1000 2000 07/247 07/252 07/253 07/255 07/258 07/259 07/260 07/261 07/262 07/263 07/264 07/265 07/266 07/267 07/268 07/269 07/270 07/271 07/273 07/274 07/275 07/276 07/277 -5 07/406 07/407 07/408 07/409 07/410 07/411 07/412 MAT [C] CMT [C] WMT [C] MAP [mm] 150 250 350 HMP [mm] 0 50 100 LMP [mm] 0 100 200 WMP [mm] Deniş Formation Soma Formation

middle lignite succession

lower lignite succession

upper lignite succession

SM-I SM-II Pollen zones SM-III SM-IV D-I D-II

are similar for each of the samples. Using a combination of all five samples, the coexistence interval for MAT covers 13 to 21.1 °C (lower boundary: Cycadaceae; upper boundary: Carpinus betulus, caroliniana), 5.5 to 15 °C for CMT (lower boundary: Cycadaceae; upper boundary: Nyssa), 23.6–28.3 °C for WMT (lower boundary: Sapotaceae; upper boundary: Quercus), 617–1613 mm for MAP (lower boundary: Cycadaceae; upper boundary: Rhus), 187–265 mm for HMP (lower boundary: Cycadaceae; upper boundary: Carpinus betulus, caroliniana), 17–83 mm for LMP (lower boundary: Rhus; upper boundary: Corylus), and 72–195 mm for WMP (lower boundary: Nyssa; upper boundary: Rhus).

The Soma macroflora of the marl-dominated lithologies over the lower lignite sequence represents a very rich association of taxa, even if cf-determinations are excluded. 79 of 111 taxa with climatic information provide a sound basis for the CoA analysis (Tables1and2). Apparently, cf. identifications of the fossil taxa primarily introduce noise to the analysis. With al-most 100 % overlapping temperature reconstruction provides highly significant results. The only outlier (Lauraceae (Lindera benzoin, Asimina triloba, Calycanthus fertilis)) requires higher WMT, in the order of 1 °C, a negligible value when considering the resolution of the data. While the actual values obtained for MAT and WMT largely confirm earlier published values, which are based on a considerably reduced preliminary taxa list, the updated CMT turns out significantly higher compared to the first estimate (Akgün et al.2007) and as a consequence, complete overlapping with values obtained from the Soma mi-croflora is obtained (Table2). The considerably higher CMT, and slight reduction on WMT obtained here are mainly due to the improvement of the NLR concept for the fossil taxa con-tributing in the analysis.

With regard to precipitation, the re-evaluation for MAP revealed a somewhat broader interval compared to the pub-lished values, now including also values slightly below 1,000 mm, and is now closer to the reconstruction based on the coeval pollen flora. The MAP reconstruction excludes a single taxon only, namely Populus euphratica (nearest living rela-tive of Populus mutabilis) as a dry outlier. The reconstruction of monthly precipitation data holds the key for assessing the seasonality of rainfall in the Miocene Soma area and is pre-sented here for the first time. HMP (wet) around 150 mm was always twice as high as WMP (warm) (around 85 mm) sug-gesting highest rainfall rates, not in the warm season. At the same time, the comparatively high WMP level is contradicto-ry to the existence of a Mediterranean type, summer-dcontradicto-ry cli-mate as today present in the study area. Nevertheless, driest month precipitation (LMP) of ca. 20–30 mm points to a sea-son with significantly reduced rainfall. Summarizing these data, the Miocene precipitation pattern of the Soma area more resembles conditions today existing in coastal areas of the western Black Sea (e.g. Zonguldak station, Cf climate with high rainfall rates in the cold season and driest conditions in spring). The only taxon in the record suggesting summer-dry conditions is Populus euphratica (NLR of P. mutabilis) which is an outlier in CoA reconstruction. However, the taxonomic integrity, already of the fossil taxon can be regarded as doubt-ful (cf. e.g. Kvaček and Walther1998).

For the middle lignite succession, climate data were extract-ed from 29 samples. MAT ranges from 17.2 to 21.1 °C and is determined by Trigonobalanus and Carpinus betulus caroliniana. The CMT coexistence interval ranges mainly be-tween 9.6 and 15 °C (lower boundary: Mastixiaceae; upper boundary: Nyssa). According to Trigonobalanus and

Table 2 Comparison of quantitative palaeoclimate results on the basis of leaf floras between current study and Akgün et al.

(2007) Leaf flora Akgün et al. (2007) 52 taxa This study 79 taxa MAT [°C] 15.3–16.5 °C

Ziziphus ziziphoides- Populus cf. balsamoides

16.8–17.3 °C

Persea indica- Buxus sempervirens

CMT [°C] 2.7–4.8 °C

Myrica lignitum - Populus cf. balsamoides

9.2–9.8 °C

Persea indica-Castanea sativa

WMT [°C] 25.7–26 °C

Ulmus carpinoides- Pinus palaeostrobus

23.6–24.7 °C

Planera aquatic-Fraxinus excelsior

MAP [mm] 1036–1237 mm

Myrica lignitum - Populus cf. balsamoides

897–1230 mm

Planera aquatica-Persea indica

HMP [mm] X 150–164 mm Engelhardia-Persea indica LMP [mm] X 22–29 mm Decodon-Ceratonia WMP [mm] X 84–85 mm Planera aquatica-Frangula

Quercus the coexistence interval for WMT is 25–28.3 °C and shows only minor oscillations. MAP coexistence intervals are between 1217 and 1613 mm on the basis of Trigonobalanus and Rhus. The interval for HMP is 254–265 mm relying on Trigonobalanus and Carpinus betulus, caroliniana. LMP co-existence intervals range mainly between 17 and 85 mm (lower boundary: Rhus; upper boundary: Carpinus betulus, caroliniana). WMP results lay between 118 and 195 mm (low-er boundary: Trigonobalanus; upp(low-er boundary: Liquidambar). The palaeoclimate data for the upper lignite succession of the Deniş Formation were determined for 7 samples with the same coexistence intervals for each of the samples, and no indication of climate changes is evident from the D-I to D-II zones (Fig.7). Taxodium and Phillyrea limit the range of MAT to 13.3 to 20.5 °C. CMT values range from 5.5 to 15.1 °C, on the basis of Cyacadaceae and Tilia. The WMT coexistence interval is 23.6–28.3 °C (lower boundary: Sapotaceae; upper boundary: Quercus) (Fig.7). The interval for MAP is comparatively broad and ranges from 650 to 1356 mm, determined by Cyrillaceae-Clethraceae and Phillyrea. The interval for HMP is between 187 and 265 mm on the basis of Cyacadaceae and Carpinus betulus, caroliniana. A second coexistence interval indicating a drier climate between 108 and 170 mm is defined by Cyrillaceae-Clethraceae and Phillyrea. LMP and WMP values give intervals of 17–71 mm and 49–92 mm respectively, both determined by Rhus and Phyllirea (Fig.7).

Quantitative palaeoclimate data indicate warm and humid conditions during the deposition of the middle lignite succes-sion. However, the calculated values for the lower and upper lignite successions provided broad ranges of the intervals. Still, an abrupt increase in Botryococus during the deposition of the upper lignite succession may have been linked to a drying event which led to a lowering of the lake-level. This is in line with a decline in warmest month precipitation coin-ciding with augmentation of Botryococcus pointing to raised salinity, brackish and oligohaline environments (Wake and Hillen1980).

So, all in all, during the early Miocene, a warm and rainy climate prevailed around Soma if we exclude some drought-tolerant plants (e.g. Chenopodiaceae-Amaranthaceae, Ephedra and Populus mutabilis) occurring only in minor amounts. However, since the amounts of mega-mesothermal and mesothermal elements remained the same as in the lower and middle lignite successions (Soma Formation), a short-term drought took place, possibly at the closing stage of the lake (Deniş Formation).

Comparison with other pollen floras of Turkey

Given the palaeoecological differentiation from one region to others, it is very difficult to compare the current Miocene

study with others. We are unable to do this properly due to some reasons such as i.e. different settings, latitudinal, longi-tudinal and palaeogeographic variations and controversial ages of related basins. Taking these issues into consideration, it seems that the floras from western Turkey are most suitable for possible comparison. For this, a borehole drilled by a pri-vate company for coal prospecting in the Arabacıbozköy lo-cality, the closest to the Soma Basin situated approximately 50 km southwest, was studied by Akkiraz et al. (2015) who distinguished Soma and Deniş floras which did not show a distinct palaeoecological difference. The floristic composition of the Soma flora in the Arabacıbozköy locality can be corre-lated with the information from the current Soma flora includ-ing high quantities of Pinaceae, Quercus and Alnus (SM-III and SM-IV). Also, high quantities of Cupressaceae at Arabacıbozköy can be connected with the SM-I and SM-II zones of Soma flora and the D-I and D-II zones of the Deniş flora. However, there are some distinct differences in the per-centages of individual taxa. For instance, herbaceous compo-nents such as Poaceae, Asteraceae and Chenopodiaceae-Amaranthaceae have high values in the Deniş flora (Arabacıbozköy), though they are infrequent in zone D-I, and even absent in zone D-II (Fig. 5). The quantity of Botryococcus likewise is represented by high values in the Deniş flora (Soma Basin) (Fig.5). These probably would be related to change in local vegetation cover. When comparing quantitative palaeoclimate data from both regions it seems that Arabacıbozköy tended to be warmer (MAT) and wetter (MAP and LMP) during the deposition of both formations (Table3). Also, palynological associations (local pollen zones B-1, B-2 and B-3) of the Kalkım-Gönen Basin (Bengiler well; dat-ed as Aquitanian), northern Turkey, can also be well correlat-ed with the Soma flora (SM-I/IV) due to insignificant differ-ences in the pollen spectra including high quantities of undif-ferentiated Pinaceae, Cupressaceae, Quercus and Alnus, along with minor amounts of Engelhardia and Castanea-Castanopsis (Üçbaş-Durak and Akkiraz, 2016).

A marine Aquitanian flora from the Kavak Formation, southwest Turkey, was studied by Akkiraz et al. (2009) who

„

Fig. 8 Individual pollen grains accompanied by name, sample number

and local pollen zones. Scale bar represents 20μm for all photographs. a

Polypodiaceae/Thelypteridaceae, sample 07/372; SM-I. b Picea, sample

07/375; SM-II. c–e Cupressaceae, c. Sample 07/368; SM-I, d, e Sample

07/376; SM-II. f Cycadaceae, sample 07/373; SM-II. g, h Arecaceae, g sample 07/373; SM-II, h sample 07/375; SM-II. i Ephedra, sample 07/ 270; SM-IV. k Magnoliaceae, sample 07/264; SM-IV. l Liliaceae, sample 07/406; I. m Carya, sample 07/238; SM-III. n Tilia, sample 07/411; D-II. o, p Engelhardia, o Sample 07/368; SM-I, p Sample 07/375; SM-D-II. r Betula, sample 07/368; SM-I. s Zelkova, sample 07/237; SM-III. t Quercus, sample 07/372; SM-I. u Castanea-Castanopsis, sample 07/ 373; SM-II. v Nyssa, sample 07/373; SM-II. y Sapotaceae, sample 07/ 237; SM-III. z Chenopodiaceae–Amaranthaceae, sample 07/242; SM-III

c

d

e

f

g

h

p

s

u

y

z

t

i

k

_l

o

m

20

n

r

v

a

b

recorded high quantities of mixed mesophytic taxa such as Engelhardia, Quercus and Castanea-Castanopsis, along with minor amounts of conifers such as Cupressaceae and Pinaceae. This flora also includes few marine dinocycts, a back-mangrove taxon Longapertites retipiliatus and certain plicoids such as Plicapollis plicatus and P. hungaricus. One of the main differences between the Kavak and Soma is that the conifers were rich in the present study instead of the mixed mesophytic forest taxa. Another difference is that the plicoid pollen are totally absent here.

Akgün and Sözbilir (2001) studied the Chattian-Aquitanian successions from southwest Anatolian molasse basins and recognised an Aquitanian flora, which consists m a i n l y o f C u p r e s s a c e a e , P i n u s h a p l o x y l o n ty pe, Sparganiaceae, Myrica, Engelhardia and Cyrillaceae-Clethraceae coupled with minor Oleaceae, Castanea-Castanopsis Calamus and Sapotaceae. With an abundance of Cupressaceae, Engelhardia and Castanea-Castanopsis the Aquitanian flora may be correlated with the SM-I and SM-II zones of the Soma flora.

Pollen floras from other western Anatolian basins (i.e., İzmir-Tire; Aydın-Şahinali; Manisa-Çıtak; Kütahya-Seyitömer and Kütahya-Tunçbilek; Muğla-Ören; Yatağan) are less suitable for possible comparison owing to poor bio-stratigraphic evidence indicating an early to middle Miocene age sensu lato and establishing some discrepancies in the palynomorph spectra (Akgün and Akyol1987; Akgün and Akyol 1999; Yavuz-Işık 2007; Emre et al. 2011; Akkiraz

2011; Akkiraz et al. 2012; Kayseri et al. 2014; Bouchal

2019). However, the taxonomic composition and percentages of some palynomorphs of relevant basins are similar to that of the current study, indicating diverse and rich arboreal plants (AP), and relatively poor non-arboreal plants (NPP) with lim-ited in distribution on western Turkey.

Conclusions

Based on this study six local pollen zones are identified in the early Miocene of the Soma Basin. Although there are some

differences in palynomorph abundances among these local pollen zones, the main vegetation characteristics remain the same. The vegetation in the basin consists mainly of conifer-ous forests, evergreen and deciduconifer-ous mixed forests and ripar-ian forests. This is comparable to the palynological results from other Turkish Miocene basins such as Kütahya (Tunçbilek and Seyitömer subbasins), Aydın-Şahinali, İzmir-Tire, and Manisa-Çıtak. The palaeoclimate was warm with high annual rainfall during the deposition of the Soma Formation (pollen zones SM/I-IV). However, a striking in-crease in Botryococcus is observed in the local pollen zones D-I and D-II of the Deniş Formation (Soma Basin) and may indicate lower precipitation rates, as seen by a drop in warmest month precipitation. The Deniş Formation may correspond to the final stage of the paleolake.

Acknowledgements The assistance provided by Dr. Rıza Görkem Ozkay, who took part in fieldwork, is acknowledged. The authors would like thank to Dr. Dimiter Ivanov and an anonymous referee for helpful comments and suggestions. This study is a contribution to the NECLIME (Neogene Climate Evolution of Eurasia) network.

Funding information This study was supported by a research grant from

the Scientific and Technological Research Council of Turkey (TÜBİTAK

Grant Code 106Y104) and the International Bureau of the Ministry of Science and Education (BMBF).

Compliance with ethical standards

Conflict of interest The authors declare that they have no conflict of interest.

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Table 3 Results of the CoA compared with the values of Akkiraz et al. (2015)

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187–265

17–71 49–92

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