Browsing by Subject "paleoklimatologia"

In this thesis, fossilized teeth of herbivores from four sites in Western Mongolia (Altanteel, Chono-Kharyakh, Oshin-Boro-Udzyur-Ula and Khrigis Nur) are examined for their stable carbon and oxygen isotope record. The fossils date to the Late Neogene period (ca. 10-3 Ma). The aim of the thesis is to reconstruct the palaeoclimate and palaeoenvironment of Western Mongolia during the Late Neogene using the isotopic records obtained from the fossilized teeth. The enamel of fourteen teeth from Rhinoceros, Equids, and a possible Giraffid was sampled and analyzed for δ13C and δ18O-values. The analyses were conducted using well-established methods with Isotope Ratio Mass Spectrometry. The stable carbon isotopes (13C and 12C) can be used to determine, the types of plants that these animals consume. Plants can be categorized into three groups based on their photosynthesis pathways. This study focuses on the C3 -plants, typically found in moister environments, and the C4-plants, which thrive in dry conditions. Specific δ13C-values have been established for these groups: –34‰ to –24‰ for C3-plants, and –20‰ to – 9‰ for C4. The δ13C-values obtained from the teeth of herbivores can be compared to these limits, allowing evaluation of the mammals’ diets (whether they consisted of C3 or C4-plants). If C3 plants dominate the die, this would indicate a moister climate, and likely a forested environment. Conversely, the presence of C4 plants would suggest grassland areas with more arid climatic conditions. The stable oxygen record in the teeth relates to the δ18O-composition of meteoric water in the area. Analysing δ18O-values facilitates the reconstruction of the mean temperatures of the habitats and allows for a comparison of climatic factors affecting precipitation and temperature over time. The stable carbon and oxygen records are compared to reconstruct the climate and environment of Western Mongolia during the Late Neogene. The results suggest an increase in the δ13C-values over time, which indicating a shift in the animals’ diets towards a more drought-stressed C3 and C4 plant-based one. The δ18O-values, on the other hand, remain stable and do not indicate a change in temperature during the Late Neogene. Comparing both the δ13C- and δ18O- values with studies conducted in China indicates a gradual aridification in Western Mongolia and China during the Late Neogene. However, the temperatures did not change significantly, although there were most likely alternating cooler and warmer periods during the time span of 10-3 Ma.