Thesis (M.S.)--University of California, Santa Cruz, 2001. / Typescript. Includes bibliographical references (leaves 69-72).

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007. / Martial Taillefert, Committee Member ; Jay Brandes, Committee Member ; Markus Huettel, Committee Member ; Philip Froelich, Committee Member ; Ellery Ingall, Committee Member ; Richard A. Jahnke, Committee Chair.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Edward C. Theriot and Judith C. Lang. Vita. Includes bibliographical references.

Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 64-67). Also available via Humboldt Digital Scholar.

Thesis (M.Sc. Earth Sciences)--University of Waikato, 2006. / Includes bibliographical references (leaves 134-147)

Les variations latérales d'exhumation de l'Himalaya sont peu documentées, notamment dans la partie est. Dans ce mémoire, l'évolution de la chaîne himalayenne est étudiée à partir de trois coupes réalisées dans le bassin d'avant-pays mio-pliocène où l'âge des sédiments a été déterminé par magnétostratigraphie. La contribution des différents domaines sources ainsi que leur exhumation ont été définies par des analyses géochimiques (εNd) et de thermochronologie détritique (apatite et zircon). Dans la partie orientale, nos observations suggèrent que les surrections concomitantes du plateau du Shillong et du prisme Indo-Birman ont repoussé le Brahmapoutre vers 7 Ma le long du front de la chaîne himalayenne. Les résultats des analyses de thermochronologie détritique soulignent une dynamique et des vitesses d'exhumation (1,7 km/Ma) semblables à celles de la partie centrale de la chaîne, en dépit de précipitations plus intenses et malgré la présence du plateau du Shillong au sud qui pourrait avoir absorbé une partie du raccourcissement tectonique. En revanche, l'installation d'une exhumation contrastée semble légèrement plus tardive que dans la partie centrale et ouest de la chaîne. Enfin, ces travaux suggèrent qu'au niveau de la syntaxe orientale il a existé un temps de latence d'au moins 3 Ma avant l'installation d'une rétroaction tectonique-érosion dans le massif du Namche Barwa liée à l'installation d'un drainage transverse à la chaîne. Au sein même de la partie centrale de la chaîne des variations latérales d'exhumation ont été mises en évidence, notamment, la mise en place au Népal occidental d'une exhumation rapide, reconnue dès 13 Ma, alors que celle-ci semble plus tardive dans la partie orientale du Népal. L'étude de la coupe occidentale a montré que le réseau de drainage du paléo-Indus est stable dans le bassin d'avant-pays depuis le Miocène moyen. En revanche, la proportion de matériaux provenant de l'Himalaya augmente à partir du Pliocène et ceci de manière généralisée le long de la partie ouest de la chaîne, suggérant un changement drastique des conditions d'exhumation de la chaîne. L'exhumation de la chaîne himalayenne apparaît donc comme étant segmentée latéralement. La mise en place d'une exhumation contrastée et diachrone le long de la chaîne ne semble donc pas liée à d'éventuels changements climatiques qui auraient affecté la chaîne de manière globale. La dynamique d'exhumation du prisme himalayen observée actuellement semble donc liée à des hétérogénéités de la croûte indienne, qui contrôlerait la mise en place des structures profondes de la chaîne. / From west to east along the Himalayan range, exhumation rates are variable and remain poorly constrained for the most part, especially in the eastern part of the mountain belt. To better understand their variability and to determine the influence of climatic and tectonic control, this thesis investigates the evolution of the range thanks to samples collected from three sections located in the eastern, central and western parts of the Mio-Pliocene Himalayan foreland basin. In these sections, sediment depositional ages were determined using magnetostratigraphy. Sediment provenance and contribution of the main litho-tectonic source-rock units were identified using geochemical analyses (Nd), while exhumation rates were determined with detrital apatite and zircon thermochronology. In the eastern part of the Himalaya, our results from the Kameng section in Arunachal Pradesh suggest that the surface uplift of both the Shillong Plateau and the Indo-Burman range have pushed the Brahmaputra River to the north, in front of the Himalayan range at about 7 Ma. Miocene-Pliocene exhumation rates inferred from detrital thermochronology are on the order of 1.7 km/Myr for the fastest exhuming areas, which is close to the rates reported for the central part of the range. Therefore, the distribution of precipitation, as well as the Shillong Plateau uplift which may have modified the convergence rate between the Indian and Eurasian plates, seem to have minor influence on the exhumation of eastern Himalaya. However, the onset of contrasting exhumation seems to have begun somewhat earlier than in the western and central parts of the range. In addition, our results highlight a 3 Myr time-lag between the installation of the Brahmaputra as a trunk river in the eastern syntaxes, and the onset of a fast exhumation there. Within the central part of the Himalaya, our work along the Muksar section in eastern Nepal documents lateral variations in exhumation rates, as western Nepal has been exhuming rapidly since 13 Ma, whereas the onset of fast exhumation seems to have occured later in eastern Nepal. Our results from the Chinji section in Pakistan, in western Himalaya, suggest that the Indus drainage network in the foreland basin has been stable since the middle Miocene. However, the Himalayan source contribution has been increasing since the Pliocene all along the western part of the range, and this suggests that a drastic change in the exhumation dynamics of the range occurred at that time. The Himalayan exhumation seems to be divided into independent segments along the range. The lateral variability in exhumation rates and timing of changes in exhumation rates do not seem to be linked to climatic change, which should produce a global response of the range. The exhumation dynamics is more likely to be linked to the tectonics structuring the wedge, possibly controlled by the crustal heterogeneity within the Indian plate.

Experimentos em mesocosmos, por se tratarem de estudos in-situ, possibilitam extrapolar para o campo, investigações realizadas em menor escala, com maior seguridade. Em fevereiro de 2002, foram instalados às margens da represa do Lobo (22º15\'S e 47º49\'W) nove mesocosmos, construídos com plástico (PVC) em forma de hexágono com 2 metros de altura, com fundo aberto em contato com o sedimento e volume variando entre 4,5 e 5,1 m3, em função da declividade do terreno. De acordo com a resolução 20/86 do Conselho Nacional do Meio Ambiente, as concentrações máximas permitidas para os metais cobre (0,02 mg/L) e cromo (0,5 mg/L) em corpos d\'água Classe 2 foram adicionadas aos mesocosmos, originando-se triplicatas, adotando-se outros três mesocosmos como controles. O objetivo principal deste trabalho foi verificar as possíveis alterações no ambiente sedimento, particularmente o enriquecimento e a indução de toxicidade, em função da adição dos metais mencionados. Para tanto, amostras foram coletadas através de dragas e testemunhos nos tempos 0 dia (antes da contaminação), 10 dias, 20 dias e 30 dias após a contaminação (final do experimento). Em seguida, as amostras foram preparadas e submetidas às análises físicas e químicas, caracterização da macrofauna bentônica e diversos ensaios toxicológicos. A partir dos dados gerados, efetuou-se o estudo integrativo da tríade de qualidade de sedimentos. Os resultados obtidos mostraram um discreto aumento na concentração total dos metais cobre e cromo nos sedimentos dos mesocosmos contaminados em comparação aos controles, sendo verificada diminuição na abundância de organismos bentônicos e efeitos tóxicos sobre os organismos-teste submetidos a estes sedimentos. As respostas da tríade foram essenciais para a caracterização da qualidade dos sedimentos dos mesocosmos controle em relação aos dos mesocosmos contaminados. / In-situ mesocosms experiments allow the extrapolation of laboratory data to the field with high reliability. In the present study, nine hexagonal PVC mesocosms with 2 m height and 4.5 to 5.1 m3 volume were installed in contact with the sediment near the Lobo reservoir dam (22º15\'S e 47º49\'W) in february of 2002. In accordance with the National Environmental Council (CONAMA) 20/86 resolution for Class 2 water bodies, the maximum allowed concentrations of copper (0,02 mg/L) and chromium (0,5 mg/L) were added to the mesocosms (triplicate), and three other ones were used as controls. The main purpose of this study was to evaluate the possible changes in the sediment environment, particularly the enrichment and induction of toxicity, by the contamination of these metals. The sediment was sampled by means of Eckman-Birge and core samplers on the 0 (before the contamination), 10th, 20th and 30th days (end of the experiment). Afterwards, physical and chemical analyses, benthic macrofauna characterization and several toxicity assays were conducted with the samples. In order to better evaluate these results, the sediments quality triad was considered. A discrete increase in the total concentration of copper and chromium was observed in the sediments of the contaminated mesocosms when compared to the controls, as well as a reduction in the abundance of benthic organisms and toxic effects over the organisms tested with these sediments. The triad responses were essential for quality characterization of the control mesocosms sediments in comparison with the contaminated ones.

Several sediment characteristics were analyzed to determine their suitability for use as potential normalization factors for the bioavailability of neutral organic compounds sorbed to sediments. Percent organic carbon, cation exchange capacity and particle surface area were measured sediment characteristics that varied sufficiently to encompass the range in observed sediment toxicity. Laboratory sediment toxicity test data using fluoranthene suggest that there is no biologically significant correlation between sediment toxicity and sediment characteristics (organic carbon, cation exchange capacity, particle size distribution, particle surface area). Fluoranthene amended sediments with similar organic carbon contents do not yield similar toxicities due to sorbed fluoranthene and thus do not support the organic carbon normalization approach for evaluating sediment quality or for sediment criteria development.

Ph.D. (Aquatic Health) / Please refer to full text to view abstract

The purpose of the study was to examine the distributional patterns of diatoms in the surface sediments of ten southern British Columbia inlets with respect to oceanographic and hydrographic setting, and phytoplankton distribution and productivity. The study area was divided on the basis of inlet type (high, medium, and low runoff), within-inlet gradients, and zones (northern, central, and southern). A small group of species dominated the 95 sediment assemblages. There was a fairly good correlation between the biocoenoses and the thanatocoenoses in the sense that most of those species reported as dominants in the phytoplankton were also dominants in the sediment assemblages. However, there were discrepancies and these could not be explained on the basis of the relative silicification of the diatom valves. Skeletonema costatum, usually considered a weakly-silicified, dissolution-sensitive species, was abundant in British Columbia sediments. Both the pacifica and the aestivalis forms of Thalassiosira aestivalis were abundant in the phytoplankton, but only the pacifica form was preserved well in the sediments. Thalassiosira nordenskioeldii, which is found in other sediment assemblages, was rare in most British Columbia sediments. The distributional patterns of freshwater and marine littoral species appeared to be indicative of river sources entering the estuarine system. The absolute abundance of diatoms in the sediment assemblages increased from the northern to the southern zone. Within the inlets, both absolute abundance and primary productivity increased toward the mouth. Estuarine circulation did not appear to alter substantially the spatial relationship between the biocoenoses and the thanatocoenoses. In general, individual species and species-groups often exhibited distinct distributional patterns which could be related to inlet type, zonal, and within-inlet patterns. In particular, the principal coordinate analysis showed a zonal correlation between the dominant species in the sediment assemblages, and primary productivity, salinity, and temperature in the surface waters. / Science, Faculty of / Botany, Department of / Graduate