Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [45]-52).

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 174-185). Also available in electronic version. Access restricted to campus users.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Vita. Includes bibliographical references (leaves : [37]-40).

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [26]-29).

The petrologic study of cave sediments is a new field whose history dates back only about 30 years. Most previous work has been done in Europe, with very little in North America. This is the first petrologic study of sediments of Texas caves. Sediments from the 11 Central Texas caves investigated provide information on the diagenetic sequence of authigenic calcite and collophane, and add to the knowledge of the occurrence and distribution of red clays and dolomite silts. The sediments from Fyllan Cave in Travis County place a maximum date of mid-Pleistocene on the existing Colorado River terraces. X-ray analysis of clays in sediments from three caves indicates a decline in kaolinite content, confirming a drying tendency for the last 8000 years. / text

published_or_final_version / Biological Sciences / Master / Master of Philosophy

Two biomarkers, n-alkanes and alkenones, have been studied for the distribution of their relative concentrations spatially and temporally in sediments in the Pearl River Estuary. 59 modern sediments have been collected across the Pearl River Estuary and offshore Hong Kong, covering a wide range of environmental and sedimentary conditions. The relative abundances between long-chain (C27 to C33) terrestrial-derived n-alkanes, and short-chain (C18 to C22) n-alkanes which are ascribed to marine algal and bacterial production, have been analyzed as “terrestrial-to-marine n-alkane ratios”. Results show that this ratio follows a general gradient of increasing towards uplands. More detailed interpretation has revealed that this ratio is highly dependent on the proximity of the sampling site to the supply of terrestrial matters, i.e., to river mouths and lands. This finding provides fundamentals on the development of terrestrial-to-marine n-alkane ratio as a potential new proxy for terrestrial sediment flux. The newly developed potential environmental and climate proxy, the relative abundances of n-alkane compounds, is applied on analysis of a sediment core drilled in coastal marine environment offshore Hong Kong, HKUV11, which can be dated back to c. 11,000 yr BP. Alkenone unsaturation ratios are also analyzed to reconstruct post-Younger Dryas change in sea surface temperature (SST). Records show a rapid warming of the ocean surface at the start of the Holocene epoch from c. 11,000 yr BP to c. 9000 yr BP, during when the SST researched its optimum, followed by a long period of more stabilized temperatures with the presence of some short-term cold events. The terrestrial-to-marine n-alkane ratio matches well not only with the alkenone SST data in this study, but also with the bulk organic carbon geochemical data and grain size analysis of HKUV11. This suggest that the n-alkane ratio is a reliable proxy for terrestrial sediment supply in this coastal and estuarine environment, as supported by both the field studies of its natural distribution across the environmental gradient, and the successful application on an actual sediment core. The Holocene climate variability of coastal south China recovered by the HKUV11 sediment record has been compared with δ18O records from a Dongge Cave stalagmite, a Greenland ice core and the Northern Hemisphere summer insolation variability. Results show that late-Glacial to Holocene climate in coastal South China generally agrees with the trend in the distal high-latitude North Atlantic, suggesting a strong external driving force of global climate change by the NH summer insolation variability. A detailed comparison between the HKUV11 SST record and Dongge Cave Asian monsoon record reveals that the temperature in coastal south China is sensitively correlated to the strength of Asian monsoon. These results have important implications to how monsoonal winds and temperature are coupled together, and can provide insights to how they may interact under future climate change in this densely-populated region. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

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