Indiana University-Purdue University Indianapolis (IUPUI) / Drivers that influence oceanic productivity are not clearly constrained. However, sea level changes during glacial cycles have been proposed as a potential driver for productivity variations observed over warm and cold climate periods. In order to determine this, additional oceanic paleoproductivity data collection is necessary to estimate the ocean’s feedback in response to a dynamic climate. The eastern equatorial Pacific (EEP) is an ideal site for productivity studies due to its high levels of nutrients and deep upwelling. This research examines the phosphorous and barite geochemisty of four EEP sites while also comparing the sites’ glacial and interglacial productivity variations to the geochemistry and productivity results of an independent central equatorial pacific site. Phosphorus and other elemental data were collected from sites 845, 848, 849, and 853 (ODP Leg 138). Using a Ba/Ti and P/Ti proxy (“excess” proxies), distinct productivity variations during glacial and interglacial periods were observed. While the age model for these sites has been estimated, the observed variations more than likely agree with high productivity during glacial periods and lower productivity during interglacial periods. Central equatorial Pacific cores RR0603-03TC and RR0603-03JC (IODP site survey cruise for Proposal 626) have been used as a reference for geochemical concentration parameters, as well as a comparison tool for productivity variations among the central and eastern sites. The central equatorial geochemistry results provided support for sea level changes driving paleoproductivity variations. The similar variation patterns displayed by the EEP’s geochemical data in this research could provide additional support for this hypothesis.

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Made available in DSpace on 2016-03-15T19:36:30Z (GMT). No. of bitstreams: 1 Jessica Rodrigues Camara.pdf: 4063408 bytes, checksum: d160fbb4a019fe268fcee175023d69fd (MD5) Previous issue date: 2011-03-18 / In this work, it was studied the physical-mechanical properties of elastomers based on ethylene-propylene-diene monomer copolymer (EPDM) with barite addition, witch is a filler in powder form, opening way for application of these composites in the protection and shield against X radiation, in the form of aprons. These aprons come to substitute the elastomeric ones with lead filler in ergonomic and economically advantageous conditions. Elastomeric composites with different barite concentrations were studied: 50, 75, 100, 125 and 150phr (parts per hundred of ruber). Among the studied properties are distinguished: tensile strength, module strength, tear strength, compression set, hardness, fluid absorption, morphologic analysis, X-ray attenuation and equivalent thickness of attenuation in Pb. The results showed that all the compositions present a good dispersion of the filler in the matrix. It was observed that the increase of the barite concentration provokes an increase in the X-ray attenuation, equivalent thickness of attenuation in Pb, hardness, tensile strength, elasticity module, tear strength and in the compression set of composites, as well as a decrease in the oil absorption. / Neste trabalho estudou-se as propriedades dos elastômeros a base do copolímero de etilenopropileno-dieno monômero (EPDM) com a adição de barita, que é uma carga em pó, abrindo caminho para aplicação destes compostos na proteção e blindagem contra a radiação X, na forma de aventais, em substituição dos aventais a base de elastômero carregado com chumbo em condições. Foram estudados compostos elastoméricos com diferentes concentrações de barita: 50, 75, 100, 125 e 150phr (partes por 100 partes de borracha). Entre as propriedades estudadas destacam-se: resistência à tração, módulo sob tração, resistência ao rasgo, deformação permanente à compressão, dureza, absorção de fluído, análise morfológica, atenuação de raios X e espessura equivalente de atenuação em Pb. Os resultados mostraram que todas as composições apresentam uma boa dispersão da carga na matriz. Observou-se que com o aumento da concentração de barita há um aumento na atenuação de raios X, na espessura equivalente de atenuação em Pb, na dureza, na resistência à tração, no módulo de elasticidade, na resistência ao rasgo, na deformação permanente sob compressão dos compostos, bem como um decréscimo na absorção de óleo.

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<p> The BAR CLAIM GROUP is located on the western margin of the Selwyn Basin geologic province in south central Yukon. The rock sequence is eugeosynclinal in nature, belonging to the Englishman's Group of the Mississippian. Chronologically, these rocks include massive limestone, white to red chert breccia, dark grey chert breccia, chert pebble conglomerate, lithic wacke, massive barite, grey green chert, and hornblende microdiorite. The elastic units in particular appear to be correlative with the units on the eastern margin of the Selwyn Basin. </p> <p> The barite is light grey, bedded, massive, and contains rare relic rosette structures. Associated minerals include pyrite, galena and minor sphalerite. Extensive recrystallisation and mobilization has occurred, probably as a result of regional compression and faulting. The barite may have had an exhalative origin along fault or extensional zones; however, sedimentogenic sources, such as the redistribution of pre-existing barite, cannot be precluded. </p> / Thesis / Bachelor of Science (BSc)