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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 10 | Copyright
Clim. Past, 14, 1427-1440, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 17 Oct 2018

Research article | 17 Oct 2018

Middle Miocene climate of southwestern Anatolia from multiple botanical proxies

Johannes Martin Bouchal1,2, Tuncay Hüseyin Güner3,1, and Thomas Denk1 Johannes Martin Bouchal et al.
  • 1Department of Palaeobiology, Swedish Museum of Natural History, 10405 Stockholm, Sweden
  • 2Department of Palaeontology, University of Vienna, 1090 Vienna, Austria
  • 3Faculty of Forestry, Department of Forest Botany, Istanbul University Cerrahpaşa, 34473 Bahçeköy, Istanbul, Turkey

Abstract. The middle Miocene climate transition (MMCT) was a phase of global cooling possibly linked to decreasing levels of atmospheric CO2. The MMCT coincided with the European Mammal Faunal Zone MN6. From this time, important biogeographic links between Anatolia and eastern Africa include the hominid Kenyapithecus. Vertebrate fossils suggested mixed open and forested landscapes under (sub)tropical seasonal climates for Anatolia. Here, we infer the palaeoclimate during the MMCT and the succeeding cooling phase for a middle Miocene (14.8–13.2Ma) intramontane basin in southwestern Anatolia using three palaeobotanical proxies: (i) Köppen signatures based on the nearest living-relative principle; (ii) leaf physiognomy analysed with the Climate Leaf Analysis Multivariate Program (CLAMP); (iii) genus-level biogeographic affinities of fossil flora with modern regions. The three proxies reject tropical and hot subtropical climates for the MMCT of southwestern Anatolia and instead infer mild warm temperate C climates. Köppen signatures reject summer-dry Cs climates but cannot discriminate between fully humid Cf and winter-dry Cw; CLAMP reconstructs Cf climate based on the low X3.wet∕X3.dry ratio. Additionally, we assess whether the palaeobotanical record resolves transitions from the warm Miocene Climatic Optimum (MCO, 16.8–14.7Ma) to the MMCT (14.7–13.9Ma), and a more pronounced cooling at 13.9–13.8Ma, as reconstructed from benthic stable isotope data. For southwestern Anatolia, we find that arboreal taxa predominate in MCO flora (MN5), whereas in MMCT flora (MN6) abundances of arboreal and non-arboreal elements strongly fluctuate, indicating higher structural complexity of the vegetation. Our data show a distinct pollen zone between MN6 and MN7 + 8 dominated by herbaceous taxa. The boundary between MN6 and MN7 + 8, roughly corresponding to a first abrupt cooling at 13.9–13.8Ma, might be associated with this herb-rich pollen zone.

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Short summary
Verterbate fossils suggest tropical climates and environments for the middle Miocene of western Anatolia (mammal zone MN6). We used three palaeobotanical proxies and inferred warm temperate climates. The onset of Miocene cooling (middle Miocene climate transition, MMCT, 14.7–13.9 Ma) is characterized by fluctuating ratios of woody and herbaceous pollen types, while a herb-rich pollen zone indicates pronounced cooling at 13.9–13.8 Ma. Prior to the MMCT (MN5), forest vegetation prevailed.
Verterbate fossils suggest tropical climates and environments for the middle Miocene of western...