published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Applied Geosciences / Master / Master of Science

published_or_final_version / Applied Geosciences / Master / Master of Science

The objective of this project is to apply the Optical Stimulated Luminescence (OSL) technique to date the palaeo sediment from Mu Us Desert, part of the Inner Mongolia in northern China and reconstruct the palaeo environment. Five OSL samples were collected from Dagouwan, Salawusu River Valley at Inner Mongolia by Dr S. H. Li and his team in 2009. Extraction of 150μm to 180μm silt-size feldspar from collected dune sand, lacustrine facies and fluvial facies samples and running of luminescence dating therefore to obtain the age from 50ka to 90ka. Climate proxies - magnetic susceptibility, grain size, fossil vertebrates and fossil pollens have been analyzed and it is concluded that significant climate change occurred within this period, which change from domination of warm, humid and rainy summer monsoons (before 70ka) to cold, wind, windy strengthened dry winter wind and back to warm and humid again after 55ka. / published_or_final_version / Applied Geosciences / Master / Master of Science

Materials deposited in low-temperature environments are characterized by their small particle size. The activity of microorganisms in aqueous sedimentary environments may have effective impacts on the geochemical parameters, which consequently change the original mineralogical records. The characterization of the fine environmental materials, especially those related to the microbial mediation is usually overlooked, but is essential for studies in the field of environmental microbiology or records of environmental change. The Kamchatka volcanic hot springs have been extensively studied for their microbiology because of their unique geological setting and applications to our understanding of life in the extreme environment. In those hot springs, minerals commonly appear with various morphologies. The hot springs have been existed for 40,000 years. Authigenic minerals, such as clay minerals, silica, sulfur, sulfide, and sulfate were characterized. Two types of silica and silicified biota were observed. Elemental sulfur crystals were observed although they are thermodynamically unstable. Pyrite and gypsum showed high diversities in morphologies and crystal sizes. Single forms of pyrite crystals included: cube, pyritohedron, octahedron, and sphericities. Prismatic, prismatic pseudo-hexagonal, fibrous, tubular, lenticular and twinned gypsum crystals were observed. The co-existence of diverse crystal habits of gypsum implies a long-term interaction between hot spring geochemistry and the metabolisms of the microbial community. The morphology of gypsum in hot springs was compared with that of gypsum with hydrothermal genesis in Lower Cambrian black shale. The crystallization of gypsum in the black shale of the Lower Cambrian, which shows similar but less varied morphology, was influenced by post-depositional hydrothermal fluids. I suggest that the high diversities of the morphology and crystal size of gypsum in those hot springs represent the continuous mediation of microorganism, which could be used as mineral ecophysiological records of life not only on Earth, but on Mars. Comparatively, the Pearl River Delta sedimentary environments are characterized by low-temperature and different mineralogical assemblages. Based on lithological records and dating data, C/N and organic carbon isotope are used to identify alterations between terrestrial and marine depositional environments in borehole transect that build up seven stages of sedimentary records. Secondly, element intensities taken by X-ray fluorescence core scanner and %Fe(III) variation implied different sedimentary environment records (terrestrial and marine) in HKUV15. Detrital minerals and authigenic minerals (gypsum, opal, and pyrite) were observed and characterized by scanning electron microscope. Diatom and coccolithophorid genera were identified. Most of mineralogical and biological records showed depositional environments consistent with geochemical records. In the Pearl River Delta sedimentary samples, the microbial mediated mineralization only contributed a small fraction to the mineral assemblages, while in the hot springs, the microbial mediation had more influences on the nucleation of authigenic minerals, which was reflected by the high diversity of crystal size and morphology of sulfates, sulfides, and siliceous minerals. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy

published_or_final_version / abstract / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy