Messinian Vegetation and Climate of the Intermontane Florina-Ptolemais
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bioRxiv preprint doi: https://doi.org/10.1101/848747; this version posted November 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 1 Messinian vegetation and climate of the intermontane Florina-Ptolemais-Servia Basin, 2 NW Greece inferred from palaeobotanical data: How well do plant fossils reflect past 3 environments? 4 5 Johannes M. Bouchal1*, Tuncay H. Güner2, Dimitrios Velitzelos3, Evangelos Velitzelos3, 6 Thomas Denk1 7 8 1Swedish Museum of Natural History, Department of Palaeobiology, Box 50007, 10405 9 Stockholm, Sweden 10 2Faculty of Forestry, Department of Forest Botany, Istanbul University Cerrahpaşa, Istanbul, 11 Turkey 12 3National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, 13 Section of Historical Geology and Palaeontology, Greece 14 15 16 bioRxiv preprint doi: https://doi.org/10.1101/848747; this version posted November 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 17 The late Miocene is marked by pronounced environmental changes and the appearance of 18 strong temperature and precipitation seasonality. Although environmental heterogeneity is to 19 be expected during this time, it is challenging to reconstruct palaeoenvironments using plant 20 fossils. We investigated leaves and dispersed spores/pollen from 6.4–6 Ma strata in the 21 intermontane Florina-Ptolemais-Servia Basin (FPS) of NW Greece. To assess how well plant 22 fossils reflect the actual vegetation of the FPS, we assigned fossil-taxa to biomes providing a 23 measure for environmental heterogeneity. Additionally, the palynological assemblage was 24 compared to pollen spectra from modern lake sediments to assess biases in spore/pollen 25 representation in the pollen record. We found a close match of the Vegora assemblage with 26 modern Fagus–Abies forests of Turkey. Using taxonomic affinities of leaf fossils, we further 27 established close similarities of the Vegora assemblage with modern laurophyllous oak forests 28 of Afghanistan. Finally, using information from sedimentary environment and taphonomy, we 29 distinguished local and distantly growing vegetation types. We then subjected the plant 30 assemblage of Vegora to different methods of climate reconstruction and discussed their 31 potentials and limitations. Leaf and spore/pollen records allow accurate reconstructions of 32 palaeoenvironments in the FPS, whereas extra-regional vegetation from coastal lowlands is 33 likely not captured. 34 35 Keywords 36 Biome reconstruction, proxy biases, climate reconstruction, plant macrofossils, dispersed 37 pollen, light and scanning electron microscopy 38 39 1. Introduction 40 The late Miocene (11.6–5.3 Ma) marks the time in the Neogene (23–2.58 Ma) with the largest 41 shift from equable climate to strong latitudinal temperature gradients in both hemispheres 42 (Herbert et al., 2016). This is well illustrated by the global rise of C4 dominated ecosystems 43 (grasslands and savannahs in the tropics and subtropics; Cerling et al., 1997). In the 44 Mediterranean region, vegetation changes did not happen synchronously with modern steppe 45 and Mediterranean sclerophyllous woodlands replacing humid temperate forest vegetation at 46 different times and places during the middle and late Miocene (Suc, 1984; Kovar-Eder, 2003; 47 Fauquette et al., 2006; Kovar-Eder et al., 2014; Bouchal et al., 2018; Denk et al., 2018; Suc et 48 al., 2018). During the latest Miocene (5.9–5.3 Ma) the desiccation of the Mediterranean Sea 49 was caused by the isolation of the Mediterranean Sea from the Atlantic Ocean. Based on 50 palynological studies across the Mediterranean region, this event did not have a strong effect 51 on the existing vegetation. Open and dry environments existed in southern parts before, 52 during, and after this so-called Messinian Salinity Crisis (MSC). In contrast, forested 53 vegetation occurred in northern parts of Spain, Italy, and the Black Sea (Fauquette et al., 54 2006). Likewise, a vegetation gradient occurred from N and C Italy and Greece to Turkey, 55 where humid temperate forests had disappeared by the early late Miocene (Denk et al., 2018). 56 The Florina-Ptolemais-Servia Basin (FPS) of NW Greece is one of the best-understood 57 intermontane basins of late Miocene age in the entire Mediterranean region. A great number 58 of studies investigated the tectonic evolution, depositional history, and temporal constraints of 59 basin fills (e.g. Steenbrink et al. 1999, 2000, 2006), plant fossils (e.g. Knobloch & Velitzelos, 60 1986a,b; Velitzelos & Gregor, 1985; Mai & Velitzelos, 1992; Kvaček et al., 2002; Velitzelos 61 et al., 2014), and vertebrate fossils (van de Weerd, 1979; Koufos 1982, 2006; Koufos et al., 62 1991). 2 bioRxiv preprint doi: https://doi.org/10.1101/848747; this version posted November 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 63 The Messinian flora of Vegora in the northern part of the FPS is dated at 6.4–6 Ma and 64 represents the vegetation in this region just before the onset of the Messinian salinity crisis 65 (the pre-evaporitic Messinian). This flora has been investigated since 1969 (Kvaček et al., 66 2002) and represents one of the richest late Miocene leaf floras in the eastern Mediterranean 67 along with two other, slightly older, Messinian plant assemblages from the FPS, 68 Likoudi/Drimos and Prosilio/Lava (4-6 in Fig. 1; Velitzelos et al., 2014). The focus of 69 previous palaeobotanical studies in the FPS has been on macrofossils. In contrast, no 70 comprehensive study of dispersed pollen and spores has been carried out in the FPS. While 71 fruit and seed floras, to a great extent, and leaf floras, to a lesser extent, reflect local 72 vegetation in an area, dispersed pollen and spores provide additional information about the 73 regional vegetation. Therefore, a main focus of the present study is on spores and pollen of 74 the Messinian plant assemblage of Vegora. 75 We (i) investigated dispersed spores and pollen using a combined light and scanning electron 76 microscopy approach (Daghlian, 1982; Zetter, 1989; Halbritter et al., 2018) that allows a 77 more accurate determination of pollen and hence higher taxonomic resolution. We (ii) then 78 compiled a complete list of plant taxa recorded for the site of Vegora including fruits and 79 seeds, foliage, and spores and pollen. Based on the ecological properties of their modern 80 analogue taxa, we assigned the fossil-taxa to functional types (vegetation units) and inferred 81 palaeoenvironments of the FPS during the Messinian. Using leaf physiognomic 82 characteristics, we (iii) conducted a Climate Leaf Analysis Multivariate Program (CLAMP) 83 analysis (Spicer, 2008; Yang et al., 2011) to infer several climate parameters for the late 84 Miocene of the FPS. We also (iv) used a modified “Co-existence approach” (Mosbrugger & 85 Utescher, 1997) based on climatic requirements of modern analogue plant taxa to infer two 86 climate parameters and (v) a Köppen signature analysis (Denk et al., 2013; Bouchal et al., 87 2018) based on the Köppen-Geiger climate types in which modern analogue taxa of the fossil- 88 taxa occur. Finally, we (vi) discuss how well the translation of fossil plant assemblages into 89 functional types (vegetation units, biomes) works for reconstructing past environments at 90 local and regional scales. 91 92 2. Material and Methods 93 2.1. Geological setting 94 The old open-pit lignite quarry of Vegora is located in western Macedonia, NW Greece, ca. 2 95 km E of the town of Amyntaio and is part of the Neogene Florina-Ptolemais-Servia 96 intermontane basin (FPS). The FPS is part of the Pelagonian basin that extends to the north 97 into North Macedonia (Fig. 1). The NNW–SSE trending FPS is ca. 120 km long and presently 98 at elevations between 400 and 700 m a.s.l. and is flanked by mountain ranges to the east and 99 the west. Main ranges include Baba Planina (2,601 m), Verno (2,128 m), and Askio (2,111 m) 100 to the east of the basin and Voras (2,528 m), Vermio (2,065 m), Olympus (2,917 m) to the 101 west (Fig. 1). These ranges are mainly comprised of Mesozoic limestones, Upper 102 Carboniferous granites and Paleozoic schists. 103 Continuous sedimentation since 8 Ma resulted in the accumulation of ca. 600 m of late 104 Miocene to early Pleistocene lake sediments with intercalated lignites and alluvial deposits. 105 The FPS basin formed in the late Miocene as a result of NE–SW extension in the Pelagonian 106 Zone, the westernmost zone of the Internal Hellenides (Brunn, 1956; Pavlides & Mountrakis, 107 1987). A subsequent Pleistocene episode of NW–SE extension caused the fragmentation of 108 the basin into several sub-basins (Steenbrink et al., 2006). 3 bioRxiv preprint doi: https://doi.org/10.1101/848747; this version posted November 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 109 Basin fills overlay unconformably Paleozoic and Mesozoic rocks. Alpine and pre-Alpine 110 basement of the area consists of Pelagonian metamorphic rocks (gneisses, amphibolites, mica 111 schists, meta-granites and Permian to Triassic meta-sediments) and crystalline limestone of 112 Triassic–Jurassic age (carbonate cover).