Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990. / Includes bibliographical references (leaves 31-32). / by Kevin Robert Gurney. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmosphere and Planetary Sciences, 1987. / Bibliography: leaves 120-121. / by Kuanman Xu. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Bibliography: leaves 101-102. / by Peter John Sousounis. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 173-186). / The range of geologic problems that may be addressed by U-Pb geochronology is governed by the precision to which U-Pb dates can be measured, expressed as their estimated uncertainties. Accurate and precise knowledge of both the value and uncertainty of an isotopic date are imperative to its correct interpretation. This thesis focuses on quantitatively addressing the large volume of information that contributes to the calculation of published high-precision U-Pb dates. A new algorithm (Chapter 2) outlines the equations that transform measured isotope ratios, along with a host of laboratory and instrumental parameters, into a U-Pb date. The algorithm propagates all known random and systematic uncertainties, resulting in an adaptable framework will remain usable as analytical and computational advances change the main uncertainty contributions. The data reduction and uncertainty propagation algorithm, as well as a new method for calculating weighted means that correctly treats systematic uncertainties, have been incorporated into the open-source software program U-PbRedux. Chapter 3 explores the mechanisms of isotopic fractionation, the largest instrumental correction to measured U-Pb data, using a new linear regression algorithm. The algorithm rapidly regresses a straight line through large datasets in multiple dimensions using a novel simplification to the maximum likelihood objective equation, and is used to demonstrate that Pb undergoes mass-independent fractionation in the source of a thermal ionization mass spectrometer. Chapter 4 addresses the largest source of systematic uncertainty considered when confederating datasets from different labs, the calibration of the tracer used for isotope dilution. The calibration assumes only first-principles mass and purity measurements traceable to SI units, then defines a measurement model that utilizes >105 measurements in a series of overdetermined inverse problems to estimate the tracer isotopic composition. The result is a reduction by a factor of almost four in the tracer uncertainty contribution to a U-Pb date. In Chapter 5, I use the new algorithms to explore regional geology. High-precision U-Pb dates from the metamorphic core of the North Cascades and from ash beds in three fluvial basins that flank it show that Eocene magmatism, solid-state deformation, and exhumation of the metamorphic core are coincident with rapid basin subsidence. / by Noah Morgan McLean. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2001. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 47-48). / The spectral slopes of 701 S-type asteroids have been statistically shown to depend on asteroid size. The spectral reflectance data were taken during the second phase of the Small Main-belt Asteroid Spectroscopic Survey. It was concluded that larger S-type asteroids have a higher spectral slope than smaller S-type asteroids, implying that S-type asteroids are likely to be undergoing a time-dependent surface alteration process, known as space weathering. / by Lindsey Ellen Malcom. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (leaves 253-269). / by Ein-Fen Yu. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Bibliography: v. 3, leaves 513-536. / by Thomas Martin Wissler. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, June 2003. / Includes bibliographical references (leaves 139-144). / We estimate the vertical structure of tidal frequency energy at various locations in the ocean by decomposing current records from the WHOI moored buoy archive. Estimates are made of the barotropic and baroclinic modes 1-4 for multiple locations, primarily in the North Atlantic and North Pacific. Estimates are also made for energy flux rates at some locations. The implied global dissipation rate fro the internal tides is significantly below estimates from altimetry. / by Alexander Stine. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Page 238 blank. / Includes bibliographical references. / In nature, carbonates often accumulate large amounts of strain in localized shear zones. Such marble sequences play a key role in crustal deformation processes. Despite extensive field and laboratory investigation, many questions remain concerning the mechanical behavior of these rocks. For example, the mechanical behavior of different limestones and marbles differ greatly, possibly owing to the presence of chemical impurities or solid-solutes. Thus, Chapter 2 examines the effect of Mg solute, a common impurity, on the mechanical behavior of calcite rocks. The results indicate that increasing Mg content increases the strength of calcite rocks during dislocation creep. The anisotropic nature of crystal slip usually entails variations in reorientation of individual grains and heterogeneous deformation within the polycrystalline material. In Chapter 3, a new technique including a series of sample preparation and image analysis algorithms is developed to provide quantitative measurements of the scale of heterogeneities produced, and to gain fundamental insight into polycrystalline plasticity. We place particular attention on quantifying variations of strain within grain interiors and at grain boundaries, and on recognizing the relative activities of different slip systems. The quantification of grain-to-grain interactions during straining is relevant for the improvement and verification of models of polycrystalline plasticity. The strain measurements obtained from Chapter 3 are compared with predictions of grain strain and reorientation obtained from the self-consistent viscoplastic method (Chapter 4). The results suggest that the self-consistent model gives a good description of global texture, but does not always predict lattice rotation and deformation within individual grains. To predict the actual deformation of individual grains will require a quantitative consideration of the effects on local strain of grain-boundary misorientation, local strain/stress state, grain-boundary sliding, and deviations in grain geometry. / by Lili Xu. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (leaves 46-48). / by Janet Chen. / M.S.