Thesis (Ph.D.)--University of Rhode Island, 2008. / Includes bibliographical references (leaves 134-150).

Thesis (Ph. D.)--University of Cambridge, 1965. / Includes bibliographical references.

Thesis (Ph. D.)--Eidgenössischen Technischen Hochschule Zürich, 1978. / Vita: p. 163.

Thesis (Ph. D.)--Stanford University, 1982. / Includes bibliographical references (leaves 200-211).

Graduation date: 1984

Brunhes, Matuyama, Kaena and Mammoth age basaltic lava (Selkirk Volcanics - TQS) as well as interbedded sediments were sampled in west-central Yukon Territory, Canada. Paleomagnetic sampling of basalt mapped as TQS along a 370 kilometre transect suggests that early eruptions of TQS occurred coevally over a significant distance to the north of Fort Selkirk. Basal basalt at Ne Ch'e Ddhawa pre-dates continental glaciation in Yukon and is older than the Fort Selkirk Vent (Lower Mushroom), previously thought to be the oldest eruptive vent at Fort Selkirk. The high confining pressures required to form pillow lava suggest subglacial eruptions at Mushroom section. An Early Pleistocene Fort Selkirk glaciation sequence (till and outwash) was reversely magnetized and assigned to the Late Matuyama chron between oxygen isotope stages 62 and 56 inclusive. A lateral moraine on Ne Ch'e Ddhawa was reversely magnetized and therefore assigned to one of the younger Pre-Reid glaciations. i / xi, 123 leaves : ill. (some col.) ; 29 cm.

Oriented archaeomagnetic samples were collected from 158 in situ features at 33 sites in the southwestern U.S. Seventy-three independently dated features were used for analysis of secular variation. A moving-window smoothing technique with outlier rejection was developed to objectively compute a virtual geomagnetic pole (VGP) path. Weighted Fisher statistics, accounting for errors in both dating and archaeomagnetic direction, were used to compute a mean VGP and standard error (A95) within each window of time. The VGP moves from 86°N, 83°E at A.D. 750 to 74°N, 192°E at A.D. 1075, and then to 85°N, 236°E at A.D. 1425. Secular variation of the VGP ranges from .00423-.350°/yr with a median of .0359°/yr. The A95s for the VGP curve range from 1.33-5.28°. Archaeomagnetic declinations and inclinations in Tucson range from 346-359°E and 47-60°. The close agreement with a similarly constructed VGP curve for Arkansas implies a small nondipole field in North America between A.D. 1150-1450. The VGP curve is significantly different from that of R. L. DuBois. Three case histories of archaeomagnetic dating suggest the validity of the new curve. The Thellier-Thellier paleointensity experiment was performed on 187 specimens from 77 potsherds. A significant magnetic fabric anisotropy, typically 30%, was found. Using an easy-plane model of magnetization, the anisotropy correction systematically increased the paleointensities by 5%. Paleointensities were interpreted for 127 samples from 54 sherds. All ceramics were independently dated and used along with other results to construct a virtual axial dipole moment (VADM) curve. A moving-window smoother using weighted statistics within each interval of time and incorporating outlier analysis was used. The Southwestern VADM at 300 B.C. is 14 x 10('22)Am('2), decreases to 8.6 x 10²²Am² at A.D. 800, and increases to 12.9 x 10²²Am² at A.D. 1500. Paleointensities from Hohokam ceramics compare favorably with paleointensities from other Southwestern ceramics, regardless of whether the long Hohokam chronology beginning at 300 B.C. or the short chronology beginning at A.D. 500 are used. There is also reasonable agreement between the Southwest and Mesoamerican VADM records.

A monção indiana está diretamente relacionada a inversão sazonal dos ventos controlada pela migração latitudinal da Zona de Convergência Intertropical (ITCZ). Em longo período os sistemas de monções são fortalecidos em resposta a períodos interglaciais (quentes e húmidos) e enfraquecidos em resposta a períodos glaciais (frios e secos). Durante os últimos 500 mil anos o clima global tem oscilado com uma periodicidade de ∼100 mil anos sendo controlado principalmente pela forçante orbital. Dados de testemunhos do Mar da Arábia, mostram que o aporte de sedimentos fluviais ocorre principalmente na parte noroeste com valores reduzidos à sudeste onde está localizada a República das Maldivas, que compreendem uma região distante o bastante das fontes fluviais de sedimento, sendo um local ideal para a obtenção de registros de sedimentos eólicos. Dados de satélite da pluma de poeira nas quatro diferentes estações do ano mostram que as Maldivas estão fortemente sob a influência da pluma de poeira relacionada a monção de inverno com ventos vindos de nordeste, tornando esta, uma região ideal parra o estudo das condições de aridez na área fonte na massa de terra indiano-asiática. Aqui nós apresentamos dados não destrutivos em alta resolução da Fluorescência do Raio X (XRF) e de magnetismos ambiental e de rocha dos vinte metros superiores do testemunho U1471, IODP EXP. 359, compreendendo um registro continuo de 500 mil anos. As boas correlações entre os diferentes elementos associados aos sedimentos terrígenos indicam que as variações nos dados de Fe, K, Al e Ti são robustas, sendo destes, o Fe, o elemento que menos apresentou ruído. Com a premissa de que, o aumento na extensão de regiões áridas na área fonte durante períodos frios está relacionada com o aumento na quantidade de elementos terrígenos que fluíram para as Maldivas, construímos um modelo de idade correlacionando os dados de Fe com os dados de δ18O, a alta resolução dos nossos dados e a boa correlação com os dados de δ18O permitiram identificar os Marine Isotope Stages (MIS) 1 ao 14. Dados de próxies paleoclimáticos como as razões, Al/Si, Fe/K e Sr/Ca indicam eventos abruptos extremamente húmidos em especial durante a transição MIS 5-6 sucedendo em poucas centenas de anos o evento Heinrich 11 (H11). Os dados de magnetismos ambiental e de rocha apontam para forte diagênese redutora de magnetita, formando minerais compostos de sulfeto de ferro, associada com a transição sulfato metano (SMT) na coluna sedimentar, abaixo desta transição a resposta magnética fica extremamente reduzida, mas ainda conserva as variações do sinal anterior a diagênese. Dados de First Order Reverse Curve (FORC) e de X Ray Absorption Near the Edge Structure (XANES) apontam a presença de magnetita bacteriana no topo do registro, mas devido ao caráter redutor do sedimento coluna abaixo e ao tamanho extremamente reduzido, Single Domain (SD), da magnetita bacteriana, este sinal está restrito ao topo do registro. / The Indian monsoon is directly related to the seasonal inversion of the winds driven by the latitudinal migration of the Intertropical Convergence Zone (ITCZ). Over a long term, monsoon systems are strengthened in response to interglacial periods (hot and humid) and weakened in response to glacial periods (cold and dry). Over the last 500 thousand years the global climate has oscillated with a periodicity of ∼100 thousand years being controlled mainly by the orbital forcing. Data from the Arabian Sea cores show that the contribution of fluvial sediments occurs mainly in the northwestern part with reduced values to the southeast where the Republic of the Maldives is located, which comprise a region far enough from the fluvial sediment sources, being an excellent place for the obtaining records of dust. Satellite data of the dust in the four different seasons of the year show that the Maldives are strongly influenced by the winter monsoon with north-easterly winds, making this an ideal region for the study of arid conditions in the source area in the Indian-Asian landmass. Here we present non-destructive high-resolution X-ray Fluorescence (XRF) and, environmental and rock magnetisms data from the upper twenty meters of the U1471, IODP EXP. 359, comprising a continuous record of 500 thousand years. The good correlations between the different elements associated to the terrigenous sediments indicate that the variations in the Fe, K, Al and Ti data are robust, of which Fe is the least noise element. With the premise that the increase in the extent of arid regions in the source area during cold periods is related to the increase in the amount of terrigenous elements that flowed into the Maldives, we constructed an age model by correlating the Fe data with the data of δ18O, the high resolution of our data and the good correlation with the data of δ18O allowed to identify the Marine Isotope Stages (MIS) 1 to 14. Paleoclimatic proxy data as the reasons, Al / Si, Fe / K and Sr / Ca indicate extremely humid abrupt events, especially during the MIS 5-6 transition succeeding in a few hundred years the event Heinrich 11 (H11). Environmental and rock magnetism data point to strong magnetite reduction diagenesis, forming minerals composed of iron sulphide, associated with the methane sulphate transition (SMT) in the sedimentary column, below this transition the magnetic response is extremely reduced, but still conserved the variations of the pre-diagenesis signal. First Order Reverse Curve (FORC) and X Ray Absorption Near the Edge (XANES) data indicate the presence of bacterial magnetite at the top of the core, but due to the reduced character of the sediment column below and the extremely small size, Single Domain (SD), of bacterial magnetite, this signal is restricted to the top.

A monção indiana está diretamente relacionada a inversão sazonal dos ventos controlada pela migração latitudinal da Zona de Convergência Intertropical (ITCZ). Em longo período os sistemas de monções são fortalecidos em resposta a períodos interglaciais (quentes e húmidos) e enfraquecidos em resposta a períodos glaciais (frios e secos). Durante os últimos 500 mil anos o clima global tem oscilado com uma periodicidade de ∼100 mil anos sendo controlado principalmente pela forçante orbital. Dados de testemunhos do Mar da Arábia, mostram que o aporte de sedimentos fluviais ocorre principalmente na parte noroeste com valores reduzidos à sudeste onde está localizada a República das Maldivas, que compreendem uma região distante o bastante das fontes fluviais de sedimento, sendo um local ideal para a obtenção de registros de sedimentos eólicos. Dados de satélite da pluma de poeira nas quatro diferentes estações do ano mostram que as Maldivas estão fortemente sob a influência da pluma de poeira relacionada a monção de inverno com ventos vindos de nordeste, tornando esta, uma região ideal parra o estudo das condições de aridez na área fonte na massa de terra indiano-asiática. Aqui nós apresentamos dados não destrutivos em alta resolução da Fluorescência do Raio X (XRF) e de magnetismos ambiental e de rocha dos vinte metros superiores do testemunho U1471, IODP EXP. 359, compreendendo um registro continuo de 500 mil anos. As boas correlações entre os diferentes elementos associados aos sedimentos terrígenos indicam que as variações nos dados de Fe, K, Al e Ti são robustas, sendo destes, o Fe, o elemento que menos apresentou ruído. Com a premissa de que, o aumento na extensão de regiões áridas na área fonte durante períodos frios está relacionada com o aumento na quantidade de elementos terrígenos que fluíram para as Maldivas, construímos um modelo de idade correlacionando os dados de Fe com os dados de δ18O, a alta resolução dos nossos dados e a boa correlação com os dados de δ18O permitiram identificar os Marine Isotope Stages (MIS) 1 ao 14. Dados de próxies paleoclimáticos como as razões, Al/Si, Fe/K e Sr/Ca indicam eventos abruptos extremamente húmidos em especial durante a transição MIS 5-6 sucedendo em poucas centenas de anos o evento Heinrich 11 (H11). Os dados de magnetismos ambiental e de rocha apontam para forte diagênese redutora de magnetita, formando minerais compostos de sulfeto de ferro, associada com a transição sulfato metano (SMT) na coluna sedimentar, abaixo desta transição a resposta magnética fica extremamente reduzida, mas ainda conserva as variações do sinal anterior a diagênese. Dados de First Order Reverse Curve (FORC) e de X Ray Absorption Near the Edge Structure (XANES) apontam a presença de magnetita bacteriana no topo do registro, mas devido ao caráter redutor do sedimento coluna abaixo e ao tamanho extremamente reduzido, Single Domain (SD), da magnetita bacteriana, este sinal está restrito ao topo do registro. / The Indian monsoon is directly related to the seasonal inversion of the winds driven by the latitudinal migration of the Intertropical Convergence Zone (ITCZ). Over a long term, monsoon systems are strengthened in response to interglacial periods (hot and humid) and weakened in response to glacial periods (cold and dry). Over the last 500 thousand years the global climate has oscillated with a periodicity of ∼100 thousand years being controlled mainly by the orbital forcing. Data from the Arabian Sea cores show that the contribution of fluvial sediments occurs mainly in the northwestern part with reduced values to the southeast where the Republic of the Maldives is located, which comprise a region far enough from the fluvial sediment sources, being an excellent place for the obtaining records of dust. Satellite data of the dust in the four different seasons of the year show that the Maldives are strongly influenced by the winter monsoon with north-easterly winds, making this an ideal region for the study of arid conditions in the source area in the Indian-Asian landmass. Here we present non-destructive high-resolution X-ray Fluorescence (XRF) and, environmental and rock magnetisms data from the upper twenty meters of the U1471, IODP EXP. 359, comprising a continuous record of 500 thousand years. The good correlations between the different elements associated to the terrigenous sediments indicate that the variations in the Fe, K, Al and Ti data are robust, of which Fe is the least noise element. With the premise that the increase in the extent of arid regions in the source area during cold periods is related to the increase in the amount of terrigenous elements that flowed into the Maldives, we constructed an age model by correlating the Fe data with the data of δ18O, the high resolution of our data and the good correlation with the data of δ18O allowed to identify the Marine Isotope Stages (MIS) 1 to 14. Paleoclimatic proxy data as the reasons, Al / Si, Fe / K and Sr / Ca indicate extremely humid abrupt events, especially during the MIS 5-6 transition succeeding in a few hundred years the event Heinrich 11 (H11). Environmental and rock magnetism data point to strong magnetite reduction diagenesis, forming minerals composed of iron sulphide, associated with the methane sulphate transition (SMT) in the sedimentary column, below this transition the magnetic response is extremely reduced, but still conserved the variations of the pre-diagenesis signal. First Order Reverse Curve (FORC) and X Ray Absorption Near the Edge (XANES) data indicate the presence of bacterial magnetite at the top of the core, but due to the reduced character of the sediment column below and the extremely small size, Single Domain (SD), of bacterial magnetite, this signal is restricted to the top.

The Roza flow of the Columbia River Basalt group in Washington State U.S.A. extruded at about 15 Ma during intermediate geomagnetic polarity. The Roza is underlain by normal polarity flows and overlain by reversed units. The Roza is an extensive flow, up to 60 in thick. As the remanence-blocking isotherms progressed into the flow, it recorded a short continuous segment of the transitional geomagnetic field. Our studies show limited thermal remagnetization in the underlying flow, and we infer that groundwater was effective in extracting the heat. The extent of basement heating was further reduced by the insulating scoria immediately beneath Roza. Hence, the Roza flow cooled symmetrically from its top and base. Samples from the drilicores acquired drilling induced remanent magnetization (DIRM), shown to be well modelled as an isothermal remanent magnetization produced in nonuniform fields of the order of 10 mT at the rim of the drillstring. Alternating field demagnetization was usually successful in removing the DIRM. The remanence stability is higher in the top third of Roza, due to smaller magnetic particles, than in the lower two thirds of the flow, where the magnetic properties are nearly uniform. The stability profile corresponds to the entablature/colonnade subdivision. High temperature subsolidus oxidation of the titanomagnetites increased with height in the flow, altering the primary symmetric intraflow distribution. The declination of the Roza flow sampled at numerous outcrops is consistently about 189°. In a 54 m drillcore section, Roza inclinations become more negative towards the flow interior, consistent with its magnetostratigraphic position. Superimposed is a symmetric, rapid change in inclination from -2 to -15° and back to -5°. The flow's thermal history predicts that these fluctuations have a characteristic time between 15 and 60 years, such that the inclination changed at a rate of 1/2 to 2° per year, showing that the directions of this transitional field fluctuated several times more rapidly than the present geomagnetic field. However, considering the generally reduced intensity during transitions, these fluctuations might not be unusual. / Graduation date: 1990