Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"Sea-floor spreading"”.
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Heat loss and hydrothermal ciruculation due to sea-floor spreading.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1974.
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A combination of apatite fission track and (U-Th)/He thermochronometers to constrain the escarpment evolution in south eastern Australia: a case study of high elevation passive margins
… of the landscape to the continental breakup and sea-floor spreading of the Tasman Sea (85 Ma). The three prevailing models of escarpment evolution namely retreat into a downwarped rift shoulder, escarpment retreat and excavation in place on a high elevation rift shoulder with flexural rebound are …
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The stratigraphy and structural evolution of the late Proterozoic Gariep belt in the Sendelingsdrif-Annisfontein area, northwestern Cape Province
… (Rosh Pinah Formation) were shed. During the sea-floor spreading stage, a shallow-water carbonateclastic unit, the Hilda Sequence, was deposited. Conglomerates, quartzites, and schists with resedimented gravity-flow characteristics (Wallekraal Formation) are sandwiched between lower and upper …
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A paleomagnetic study of early tertiary basalts in West Texas
… since early Tertiary time, and that the rate of sea floor spreading at present may be low relative to what it has been.
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Geology of the passive margin off New England
… volcanics. Continental separation occurred and sea-floor spreading began 195-190 my B.P. The boundary between "normal" continental crust and crust radically altered by fracturing and intrusion may be represented by a pronounced basement "hinge zone". Prior to margin subsidence, extensive sub- …
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Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers
Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation …
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The seismic attenuation structure of the East Pacific Rise
… three-dimensional tomographic imaging of a fast-spreading ridge. The experiment location at 9°30'N on the East Pacific Rise is the site of a strong mid-crustal seismic reflector which has been inferred to be the roof of a small axial magma chamber at about 1.6 km depth. A spectral method is used …
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The sedimentology and lithostratigraphy of the Upper Jurassic Lourinha formation, Lusitanian Basin, Portugal
… a semi-arid/sub-tropical climate with markedly seasonal rainfall. The fan systems,confined to the western margin of the basin, passed laterally into meandering fluvial systems, the deposits of which form the Porto Novo member.<br></br><br></br>A marine transgression from the south resulted in …
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MAGANOM : a computer program for the modeling and interpretation of marine magnetic anomalies with an example from the Cayman Trough, northwest Caribbean Sea
… The principal use of the program is to model sea floor spreading anomalies. It can also calculate and display the anomalies above magnetic bodies with irregular shapes. Designed primarily as a research tool, MAGANOM can also be used to teach the theory of magnetic anomaly formation at the …
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Seismic constraints on shallow crustal processes at the East Pacific Rise
… at mid-ocean ridges. The emphasis is upon fast-spreading ridges, and the use of seismic techniques to image the uppermost several hundred meters of the crust. We present the results of nine on-bottom seismic refraction experiments carried out over young East Pacific Rise (EPR) crust. The …
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Geochemical tracers of processes affecting the formation of seafloor hydrothermal fluids and deposits in the Manus back-arc basin
… (REE), heavy metal, metalloid concentrations) of seafloor vent fluids and related deposits from hydrothermal systems in the Manus back–arc basin (Eastern Manus Basin, EMB and Manus Spreading Center, MSC) are used to investigate processes that affect their formation. Processes responsible for …
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Ridge segmentation, tectonic evolution and rheology of slow-spreading oceanic crust
… tectonic processes along mid-ocean ridges. Slow-spreading ridges, such as the Mid-Atlantic Ridge, are discontinuous and composed of ridge segments. Segments are thus fundamental units of magmatic accretion and tectonic deformation that control the evolution of the crust. The objective of this …
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Variations in structure and tectonics along the Mid-Atlantic Ridge, 23⁰N and 26⁰N
… that the formation of ocean crust at slow spreading centers is not a simple two-dimensional process in which crustal accretion occurs uniformly both along the ridge axis and with time. Rather, it has been proposed that the ridge axis can be divided into a number of distinct segments or …
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The crustal structure and subsidence history of aseismic ridges and mid-plate island chains
… of the Ninetyeast and Walvis Ridges near spreading centers on young lithosphere with flexural rigidities at least an order of magnitude less than those typically determined from flexural studies in older parts of the ocean basins. As the lithosphere cools and thickens, its rigidity …
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Geothermal processes at the Galapagos Spreading Center
… of the heat flow field of the Galapagos Spreading Center in an area of about 570 km2 reveal the planform of the conductive flux and permit the first truly areal estimate of the near-axis heat flux for comparison with theoretical plate cooling models. The intrusion process and associated …
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Seismic and magnetic constraints on the structure of upper oceanic crust at fast and slow spreading ridges
… upper crust at two contrasting ridges-the fast spreading East Pacific Rise (EPR) and the slow spreading Mid-Atlantic Ridge (MAR)-to build a more complete understanding about the roles of volcanic emplacement, tectonic disruption and hydrothermal alteration in the near-ridge environment. A …
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The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges
… to interpret the structural development of slowspreading ridge segments by: 1) delineating the nature, magnitude, and relative importance of primary tectonic and volcanic processes that control crustal morphology, 2) investigating the spatial and temporal variability of these processes, and 3) …
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The evolution of the Indian Ocean triple junction and the finite rotation problem
… of the plates around the Labrador Sea triple junction at the times of anomalies 24 (56 Ma) and 21 (50 Ma). The region of uncertainty of the Greenland-North America finite pole is mapped for each reconstruction, and it demonstrates that consideration of the three plate system yields …