Typescript, etc. / Digitized by Kansas State University Libraries

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Not Available / text / text

Not available / text / text

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 160-174).

Seven distinctly different museum-quality concretionary morphotypes of elongate, spheroidal, banded, botryoidal, columnar, rosette, and speleothem in regolith at two small sites at the base of the Meski Plateau near Erfoud, Morocco are described. Although most are isolated hand samples, the largest concretions are meter-sized blocks. Not one sample resembles any surrounding outcrop or bedrock. The barite rosettes formed first via periodic mixing of Ba2+/SO42- saturated solutions. They provided nuclei for cyclical precipitation-based concentric concretion development. The speleothem formed via precipitation from a carbonate-saturated solution in a large void within porous sandstone. The sand concretions formed when calcite precipitated around grains in unconsolidated quartz sands with cyclic fluctuation of Ca2+/CO32- saturated ground water. Petrographic analyses, stable isotope data, sample morphology, coupled with light and scanning electron microscopy indicate that microbial processes induced the periodic cement precipitation that produced the unique concretions.

<p> Concretions in a zone about 4 m. below the Tichenor Limestone formed just below the sediment water interface. Their growth was initiated about an organic-rich fossil cluster and was probably completed before they were more than 5 to 8 m below the sediment surface. Chemical products of organic decay, notably bicarbonate ions and ammonia, diffused outward, raising the pH and precipitating calcite from connate waters already nearly saturated with respect to calcium carbonate. These conclusions derive from the shape of the concretions, from their relation to the enclosing shales, and from their overall structure , particularly the position of pyritic fossil clusters. The relative volumes of soluble material (calcite) in the concretions are consistent with relative pore volumes through the upper 5 m. of recent, fine-grained, clayey sediments. The postulated genetic sequence agrees with recent work on carbonate diagenesis. Restriction of the concretions to discrete layers was most probably due to a widespread comnbination of high rates of organic productivity, high rates ·of sedimentation, and low rates of water circulation, that lasted a short period of time and resulted in the rapid burial.of much undecomposed organic material. </p> / Thesis / Master of Science (MSc)

<p> Study of the ecology of concretion and host sediment fossils from a shell bed in middle Bajocian clays of northwestern Germany indicates a predominantly epifaunal suspension-feeding community living on a firm mud bottom. The shell bed, firm bottom and low turbidity required by suspension feeders suggests a hiatus or reduced sedimentation at the time. Depth estimates of 50 to 150 m are indicated by ammonite and belemnite siphuncle and septal strength indices.</p> <p> Preservation of calcitic fossils is excellent in both concretions and host sediments. Aragonitic fossils show good preservation in the concretions. Aragonite has been replaced by at least two generations of calcite. Preservation in the host sediments is poor. Pyrite is common in void spaces of concretion fossils but less so in those from the host sediments.</p> <p> Eight concretions were studied, containing numerous Stephanoceras mutabile (macroconch) and Stephanoceras quenstedti (microconch). These are of opposite sexes but are not a dimorphic pair.</p> <p> Distribution of shell debris and other fossils within the concretions suggests that the ammonites were swept by currents into shallow depressions in the sea floor lined with shell debris. Such depressions have been observed in modern sediments as the result of the feeding activity of rays. The presence of currents is indicated by the southwest orientation of belemnite rostra in the host sediments. Carbonate content of concretion matrix is high indicating concretion growth in very fluid muds. This contrast with the firm bottom indicated by fossil ecology suggests rapid burial of the benthic community by either a mudflow or a sudden, large increase in sedimentation. Concretion growth was initiated by decomposition of organic matter within the mud.</p> / Thesis / Master of Science (MSc)

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-07-13T16:00:55Z No. of bitstreams: 2 Dissertação - Angélica Pires Batista Martins - 2017.pdf: 3335884 bytes, checksum: 89378cfa32c3cf46f97258266490ea63 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-17T13:34:10Z (GMT) No. of bitstreams: 2 Dissertação - Angélica Pires Batista Martins - 2017.pdf: 3335884 bytes, checksum: 89378cfa32c3cf46f97258266490ea63 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-17T13:34:10Z (GMT). No. of bitstreams: 2 Dissertação - Angélica Pires Batista Martins - 2017.pdf: 3335884 bytes, checksum: 89378cfa32c3cf46f97258266490ea63 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-04-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Ferruginous features occur frequently in soils of the Araguaia river plain, where profiles can be verified completely dominated by these characteristics. The objective of this study was to evaluate the physical variations in the plinthite and petroplinthite, considering: a) the compressive strength and stability of plinthic materials present in soils of the Araguaia river plain under natural drying and in a forced ventilation oven for different periods; b) the influence of different solutions and periods of immersion in the reversibility of hardening of plinthite and petroplinthite of the Araguaia river plain soils, both with the purpose of subsidizing the classification of these features. The study was carried out in five soil profiles in the Araguaia river flood plain, in Luiz Alves, district in the municipality of São Miguel do Araguaia, Goiás. A soil profile was also studied in Terezópolis de Goiás, Goiás, in the João Leite riverside flood plain. Soils samples were collected with PVC cylinders, directly in the plinthic horizons. From these samples were extract subsamples of plinthite and matrix of the soil. Homogenous samples of petroplinthite were also collected and separated into subsamples. Two experiments were carried out: in the first, plinthite, matrix of the soil and petroplinthite subsamples were submitted to two types of drying: in the natural environment and in a forced ventilation oven, and in the second, plinthite and petroplinthite subsamples were submitted to five hydration treatments: natural water, calcium carbonate solution, sodium hydroxide solution, sodium hydroxide + sodium hexametaphosphate solution and acid solution. The periods determined for the evaluations were 10, 20, 40, 80 and 160 days. The degrees of dispersion and stability and the compressive strength were evaluated. For the plinthite and petroplinthite of the same profile, there is a great variability of behavior as to the applied compression strength, which is associated with the iron contents that compose them. The immersion of plinthite and petroplinthite in solutions composed of chemical agents affects the dispersion, and the plinthite is more susceptible to the alkaline agents, with reduction of the compressive strength exercised. / Feições ferruginosas ocorrem com frequência em solos da planície do rio Araguaia, onde podem ser verificados perfis completamente dominados por essas características. Este estudo objetivou avaliar as variações físicas na plintita e na petroplintita, considerando: a) a força de compressão e estabilidade de materiais plínticos presentes em solos da planície do rio Araguaia sob secagem natural e em estufa de ventilação forçada por períodos distintos; b) a influência de diferentes soluções e períodos de imersão na reversibilidade do endurecimento de plintita e petroplintita de solos da planície do rio Araguaia, ambos com finalidade de subsidiar a classificação dessas feições. O estudo foi realizado em cinco perfis de solos na planície de inundação do rio Araguaia, em Luiz Alves, distrito no município de São Miguel do Araguaia, Goiás. Para comparação entre os materiais plínticos, foi também estudado um perfil de solo no município de Terezópolis de Goiás, Goiás, na planície de inundação do ribeirão João Leite. Amostras de solos foram coletadas com auxílio de cilindros de PVC, diretamente nos horizontes plínticos. Dessas amostras foram separadas subamostras de plintita e matriz do solo. Foram também coletadas amostras homogêneas de petroplintita, igualmente separadas em subamostras. Foram desenvolvidos dois experimentos: no primeiro, subamostras de plintita, matriz do solo e petroplintita foram submetidas a dois tipos de secagem: em ambiente natural e em estufa de ventilação forçada e no segundo, subamostras de plintita e petroplintita foram submetidas a cinco tratamentos de hidratação: água natural, solução de carbonato de cálcio, solução de hidróxido de sódio, solução de hidróxido de sódio + hexametafosfato de sódio e solução ácida. Os períodos determinados para as avaliações foram 10, 20, 40, 80 e 160 dias. Foram avaliados os graus de dispersão e estabilidade e a resistência à compressão. Para a plintita e petroplintita de um mesmo perfil, existe grande variabilidade de comportamento quanto à força de compressão aplicada, a qual é associada aos teores de ferro que as compõem. A imersão da plintita e petroplintita em soluções compostas por agentes químicos afeta a dispersão, sendo que a plintita é mais susceptível aos agentes alcalinos, com redução de força de compressão exercida.