Quercus praedelavayi Xing Y.W. et Zhou Z.K. sp. nov. is reported from the upper Miocene of the Xianfeng flora in central Yunnan, southwestern China. The fossil species is identified based on the detailed leaf morphological and cuticular examinations. The primary venation is pinnate and the major secondary venation is craspedodromous with regular spacing. Stomata are anomocytic and occur on abaxial epidermis. Trichome bases are unicellular and multicellular. The new fossil species shows the closest affinity with Quercus delavayi, an extant species distributing in southwestern China. The responses of the functional leaf traits to the climate change were studied by comparing the leaf characters of fossil species and its nearest living relative. The stomatal density of Q. praedelavayi is higher than Q. delavayi, which suggests a lower palaeoatmospheric CO2 concentration during the late Miocene. The trichome base density of Q. praedelavayi is higher than the extant Q. delavayi. Considering the palaeoclimatic reconstruction of Xianfeng flora, it rejected the hypothesis that increase in trichome density is an adaptation to the drier environment.

Quercus praedelavayi Xing Y.W. et Zhou Z.K. sp. nov. is reported from the upper Miocene of the Xianfeng flora in central Yunnan, southwestern China. The fossil species is identified based on the detailed leaf morphological and cuticular examinations. The primary venation is pinnate and the major secondary venation is craspedodromous with regular spacing. Stomata are anomocytic and occur on abaxial epidermis. Trichome bases are unicellular and multicellular. The new fossil species shows the closest affinity with Quercus delavayi, an extant species distributing in southwestern China. The responses of the functional leaf traits to the climate change were studied by comparing the leaf characters of fossil species and its nearest living relative. The stomatal density of Q. praedelavayi is higher than Q. delavayi, which suggests a lower palaeoatmospheric CO2 concentration during the late Miocene. The trichome base density of Q. praedelavayi is higher than the extant Q. delavayi. Considering the palaeoclimatic reconstruction of Xianfeng flora, it rejected the hypothesis that increase in trichome density is an adaptation to the drier environment.

Twenty-one fossil foliage, identified as Fokienia shengxianensis sp. nov. (Cupressaceae), were collected from the upper Miocene Shengxian Formation in Tiantai and Ninghai counties, Zhejiang Province of eastern China. These fossils can likely be distinguished from other extant genera in the family Cupressaceae s.l. except Fokienia by leaf external morphology alone. Foliar cuticular comparison with the only modern species in this genus, Fokienia hodginsii Henry et Thomas, further suggests that the present fossil species closely resembles the modern counterpart. Paleoecologically, the occurrence of Fokienia from the Shengxian Formation appears to support that the fossil site was covered by subtropical evergreen broad-leaved forest and under warm and humid conditions during the late Miocene, consistent with evidence from previously published fossil plants.

The late Miocene Xianfeng flora of Yunnan Province, southwestern China, was chosen to reconstruct the paleoclimate and the intensity of the Asian monsoon. Three available quantitative climate reconstruction methods from fossil plants, i.e. Leaf Margin Analysis (LMA), the Climate Leaf Analysis Multivariate Program (CLAMP), and the Coexistence Approach (CA) were used in this study. MATs (mean annual temperatures) resulting from these three approaches (i.e., LMA: 17.2 ± 2.38°C; CLAMP: 15.43 ± 1.25°C; CA: 17.2-21.7°C) appear to have been higher than the present (14.9°C), suggesting a much warmer climate in the late Miocene. Both the growing season precipitation (GSP) from CLAMP (1908.7 ± 217.7. mm) and mean annual precipitation (MAP) from CA (1206.0-1613.0. mm) estimates are higher than modern values (1003.2. mm (GSP) and 1038. mm (MAP) respectively) indicating a more humid climate during the late Miocene. By comparing these with climates reconstructed from neighboring late Miocene floras, we conclude that the general late Miocene climate appears warmer and more humid than present conditions in southwestern China. Furthermore, the evident differences in estimated monthly temperatures between the summer and winter, and precipitations between the humid and dry seasons indicate the existence of seasonality, though not as strong as that of today. Difference in precipitation of dry season indicates a marked strengthening in the winter monsoon since the late Miocene. A new monsoon intensity index has also been defined based on precipitation seasonality to investigate the intensity of the Asian monsoon.

Human evolution has been linked to climate change multiple times in the literature. One of the more well-known theories is the ‘savannah’ theory, which states that walking upright became an advantageous character when climate in Africa changed causing drier environments, changing woodlands to savannahs. Human ancestors could cross open fields more easily when walking upright, therefore it was thought that climate change could be a driving factor in the change to bipedal locomotion. Five hominin species were the basis of the study presented here, showing that change towards bipedal locomotion was a mosaic process with gradual change. A review of the relevant literature shows that the timing of change in fossils to bipedal locomotion and climate change do not coincide in the interval 6-3 Ma, therefore suggesting that climate change did not drive human evolution in this case. Changes towards open landscapes with C4 grass dominance peaked at the Pliocene-Pleistocene boundary (2.6 Ma), while the first hominin species already walked completely bipedally before 3.5 Ma.

The Gray Fossil Site, northeastern Tennessee, is formed by multiple karst sub-basins filled with lacustrine sediments. The oldest sediments found were recently dated as Paleo-Eocene by palynological means, whereas the youngest sediments are considered Mio-Pliocene based on their faunal assemblage. In this study, we examined the Mio-Pliocene lacustrine sediments from the Gray Fossil Site to determine the Late Neogene floral characteristics of a site within the southern Appalachian Mountains. The Mio-Pliocene lacustrine sinkhole fill preserves a unique fossil assemblage, which includes invertebrate, vertebrate, and floral remains. Floral remains are represented by wood, seeds, leaves, and pollen grains. Forty-seven palynological samples from six different test-pits were analyzed. All pits exhibit a low pollen yield, a result of basic pH levels, drought, and fire events that occurred during deposition. The palynofloral assemblage has a low to moderate diversity and is largely dominated by a Quercus-Carya-Pinus assemblage (~ 90% of the palynoflora). The presence of Pterocarya grains supports a Late Neogene age for these lacustrine sediments. Comparison with modern pollen-based floras from North America suggests that: (1) examined pits can be discriminated into two separate groups based on their palynofloral signatures, (2) the Mio-Pliocene vegetation at the site ranged between a closed to open woodland setting, depending on the intensity and frequency of drought and fire events, and (3) the fossil palynofloral assemblage is comparable to what would be expected in the modern North American Mesophytic Forest region.

Previous biostratigraphic studies in the Indian Ocean, equatorial Pacific, Atlantic Ocean and the Caribbean Sea document the temporal disappearance of Reticulofenestra pseudoumbilicus in the late Miocene (Tortonian age). This interval has been subsequently defined as the R. pseudoumbilicus paracme. While the cause of the event remains unknown, the geographical extent and global synchronicity of the interval represent an open subject for research. Answers to these questions could help establish the biostratigraphic reliability of the interval and its use for global correlation. In this study, 49 deep-sea drilling sites spread across all major ocean basins were compiled into a biostratigraphic database and studied to evaluate the global extent and timing of the R. pseudoumbilicus paracme. To ensure accurate comparison of the studied sites, the timing of the event was estimated at all sites using the age estimates generated through Undatable MatLab software, which made use of established nannofossil bioevents as age-depth tie points for the analysis. Ages of all nannofossil bioevents were updated to the latest geological time scale. This systematic analysis reveals a prominent distribution of the paracme in the tropical and subtropical regions. The timing of the event in the tropical region appears to be synchronous, with the base around 8.8 Ma and the top of the event around 7.2 Ma. Sites in the equatorial Pacific, central Atlantic and the Indian Oceans record a similar duration of the event. The paracme had a shorter duration towards the southern higher latitudes. Although timings in southern high latitudes are diachronous compared to the tropics, the duration is consistent between sites (Sites 1088 and 1264) in the southern South Atlantic, thereby establishing a new time frame for the event in the region. This study narrows down on ODP Site 806 for a critical evaluation of the nannofossil assemblages, accumulation rates and Reticulofenestra size variation in the late Miocene, including the paracme. Thirty-four samples were collected and analysed for absolute abundance and nannofossil accumulation rates (NAR). Absolute abundance and NAR reveal three distinct stages, herein described as generally low, high, and “crashed” export production of nannofossils. The period of high NAR is characteristic of the late Miocene biogenic bloom interval (ca. 9–4.4 Ma). Importantly, the R. pseudoumbilicus paracme does not only coincide with the start of the biogenic bloom but it was also associated with remarkable changes in Reticulofenestra assemblages. Just before the base of the paracme, all except the smallest (&lt;3 µm in coccolith size) Reticulofenestra groups experienced a sharp decline in abundance. Subsequently, the relative abundance of the Reticulofenestra morphospecies indicates the dominance of bloom-forming small and medium Reticulofenestra during the late Miocene biogenic bloom interval. The end of the biogenic bloom interval is concurrent with a decrease in the contribution of small Reticulofenestra. The exact biotic and abiotic processes that led to these major shifts in plankton composition are yet to be discovered, but the findings presented herein show that the mechanisms behind the temporary disappearance of R. pseudoumbilicus in the tropics most likely involved the interplay between a broad range of ecological changes and evolutionary processes affecting the Reticulofenestra assemblages. / <p>The work for this thesis was financially supported by the Erasmus Mundus Joint Master Degree PANGEAprogramme.</p>

In order to understand Mio-Pliocene floristic characteristics of the southern Appalachian Mountains, 47 palynological samples from six different testing-pits across the Gray Fossil Site (GFS) were analyzed. The site exhibits a low pollen yield resulting from basic pH levels, drought, and fire events occurring during deposition. The palynofloral assemblage has a low to moderate diversity, and it is largely dominated by Quercus-Carya-Pinus (~90% of the palynoflora). The reported presence of Pterocarya grains supports a Late Neogene age for the lacustrine sediments. Comparison with modern pollen-based floras suggests that: (1) the Mio-Pliocene Oak-Hickory-Pine association varied in structure between a woodland to woodland/savanna, depending on the intensity and frequency of drought, fire events and herbivory, (2) pits show different structure of the co-dominant genera, which indicate alternating composition of the vegetation, and (3) in term of modern vegetation, the GFS flora corresponds well with the Mesophytic Forest region.