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Middle Miocene climate of southwestern Anatolia from multiple botanical proxies

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 (14.8–13.2 Ma) 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, 16.8–14.7 Ma) to the MMCT (14.7–13.9 Ma), and a
more pronounced cooling at 13.9–13.8 Ma, 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 13.9–13.8 Ma,
might be associated with this herb-rich pollen zone.
