Thesis (M.S. - Geology)--University of Arizona. / Bibliography: leaves 33-34.

Thesis (Ph.D.) - James Cook University of North Queensland, 1970. / Typescript (photocopy) Includes bibliography.

Thesis (M. Sc.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 116-120)

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 227-246).

Thesis--Utrecht. / "Stellingen": [2] p. inserted. Summary in Dutch. Vita. Includes bibliographical references (p. 151-160).

Thesis (Ph. D.)--Oregon State University, 2005. / Printout. Includes folded map in pocket. Includes bibliographical references (leaves 144-155). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1949. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [i]-iv).

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 162-175). Also available on the World Wide Web.

<p> Mickey Springs in the Alvord Desert, southeast Oregon, is analogous to other Basin and Range hydrothermal systems where the requisite conditions of heat source and permeable pathways are met through crustal thinning due to normal faulting. This study examines the morphology and lifespan of near-surface spring features through use of ground penetrating radar, thermoluminescence (TL) dating, and elevation modeling. Duration of hydrothermal activity at Mickey Springs has not previously been determined, and age determinations of sinter at the site are conflicting. The reason for and timing of this change in silica saturation in the hydrothermal fluid has not been resolved.</p><p> Three morphologies of silica sinter deposition have been identified at Mickey Springs. These are (1) well-sorted, fine-grained sandstone with ripple marks, cross beds and preserved root casts, to poorly-sorted conglomerate of primarily basalt clasts, both cemented by coeval silica deposition, (2) large depressions (12-32 m diameter) rimmed with sinter, characterized by fine silt and clay blanketing a sinter apron and infilling the central depression, and (3) quaquaversal sinter mounds identified by outcropping pool-edge sinter typically surrounding a shallow depression of loose sediment.</p><p> Silica-cemented sandstone and conglomerate were the first features formed by coeval hydrothermal processes at the site, and were emplaced prior to 30 kya as suggested by structural and stratigraphic relationships. Structure between two interacting fault tips may have constrained the extent of silica cementation. By 30 kya, a left-stepping fault oriented roughly north/south further constrained the near-surface permeable zone. TL dates from sediment stratigraphically below and above sinter aprons around mounds and depressions (former spring vents) indicate sinter deposition between 30 and 20 kya. Location of these features was dictated by development of the left-stepping fault. As pluvial Lake Alvord filled at the end of the Pleistocene, lake sediment filled most vents, which were largely inactive, with fine-grained silt and clay.</p><p> Today, hydrothermal activity persists in two modes: (1) The current high-temperature springs, steam vents and mudpots concentrated in a 50 x 50 m area south of the sinter mounds and depressions, and (2) scattered springs and steam vents that exploit previous permeable pathways that once provided the hydrothermal fluid which precipitated the sinter aprons. Currently there is no active silica sinter deposition at Mickey Springs.</p><p> Structures and stratigraphic relationships identified through this study favor a transport-limited and structurally controlled model of fluid transport. Sinter deposition is determined to have occurred before the most recent highstand of pluvial Lake Alvord. A climate driven model, where groundwater recharge from pluvial Lake Alvord circulates to a deep heat source and enhances spring discharge, is not supported by these findings, as no evidence was found for sinter precipitation after the drying of the lake. Future studies of other hydrothermal systems in the Basin and Range may reveal that permeable pathways along local structures are the primary drivers in this region.</p>

Made available in DSpace on 2014-06-11T19:32:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-19Bitstream added on 2014-06-13T20:03:39Z : No. of bitstreams: 1 corradini_fa_dr_rcla.pdf: 3741005 bytes, checksum: 577fc274e91bed122eba3694a809a244 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O megaleque fluvial do São Lourenço é um sistema deposicional que vem sendo construído pelo rio São Lourenço, desde o Pleistoceno, na porção nordeste da bacia sedimentar do Pantanal Mato-Grossense. Com base na interpretação de imagens orbitais e de dados de campo, foram reconhecidos três grandes compartimentos geomorfológicos no megaleque: a) uma extensa planície fluvial pleistocênica dissecada; b) um cinturão de meandros de idade holocênica, ainda ativo nas porções média/superior do megaleque, mas abandonado na sua porção distal; um lobo deposicional moderno composto por vários lóbulos deposicionais. Depósitos de diferentes compartimentos foram amostrados com vibrotestemunhador, sendo as facies sedimentares descritas e interpretadas em termos de processos e de ambientes deposicionais. As idades dos depósitos dos diferentes compartimentos foram obtidas por meio de datação pelo método de luminescência oticamente estimulada (LOE), o que permitiu a proposição de um modelo evolutivo para a área estudada. Na planície aluval dissecada foram reconhecidas paleorredes de canais distributários formados por lobos ativos durante o Pleniglacial médio, entre 64,8 e 28,5 ka AP. A planície aluvial dissecada foi submetida a processos erosivos, existindo na sua superfície uma rede de canais tributários, que drenam as águas das chuvas para as planícies fluviais periféricas dos rios Cuiabá e Piquiri. A maior evidência do evento de dissecação, que do final do Pleistoceno ao Holoceno superior, é a existência de um vale inciso na porção media/superior do megaleque, cortando os depósitos pleistocênicos dos lobos antigos. O vale tem direção N65E, condicionado pela falha de São Lourenço, e nele se encontra alojado o cinturão de meandros formado por agradação fluvial... / The São Lourenço fluvial megafan is a depositional system which has been built by the São Lourenço river since the Pleistocene in the northeastern region of the Pantanal sedimentary basin of Mato-Grosso State. Based on the interpretation of orbital images and collected data field, three major geomorphological compartments of the megafan were recognized: a) an extensive fluvial plain dissected in the Pleistocene; b) a meandering belt of Holocene age, still active in middle and upper parts of the megafan but abandoned in its most distal portion; and c) a modern depositional lobe consisting of several depositional lobes. Deposits of different compartments were sampled with vibrocorer and the recovered sedimentary facies have been described and interpreted in terms of processes and depositional environments. The ages of the deposits of the different compartments were obtained from dating by the optically stimulated luminescence method (OSL), which allowed the proposition of an evolutionary model for the study area. In the dissected alluvial plain, distributary paleochannels were recognized and formed lobes during the active Middle Pleniglacial, between 64,8 and 28,5 ka BP. The dissected alluvial plain was subjected to erosion, identified through the existence on its surface of a tributary drainage network which drains rain water to the peripheral alluvial plains of the Cuiabá and Piquiri rivers. The strongest evidence for dissection of the event, which starts from the late Pleistocene to the Holocene, is the existence of a valley in the middle/upper portion of the megafan, cutting through the Pleistocene deposits of ancient lobes. The valley has a N65E direction, conditioned by the São Lourenço fault, and it is housed in the fluvial meandering belt formed by aggradation of the valley during the Holocene. The heights of the... (Complete abstract click electronic access below)