Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006. / Includes bibliographical references (p. 19-22). / Rising over 5 km along the border of Uganda and the Democratic Republic of the Congo, the Rwenzori Mountains represent an extreme example of basement rift-flank uplift in the western branch of the East African Rift, a phenomenon common throughout the East African Rift System and characteristic of continental rift systems in general. A thermochronologic study combining (U-Th)/He and U-Pb analysis of apatite, titanite, and zircon separated from crystalline basement rocks was conducted across the Rwenzori block to characterize the timing and rate of rift-flank exhumation related to continental extension in east-central Africa. The thermochronologic data coupled with field and remote sensing observations make the case for recent and non-steady state uplift of the massif. Uranium-lead thermochronology indicate that, prior to Upper Neogene rifting, the rocks of the Rwenzori experienced a protracted history of slow cooling without major tectonothermal perturbation since at least the Paleoproterozoic (ca. 1900 Ma). / (cont.) Stream channel steepness profiles and thermochronometry along the western slope of the range show it to be the main active scarp that accommodates uplift. Relatively old (U-Th)/He zircon and apatite dates (>400 Ma, >70 Ma respectively) along the high peaks and eastern slope of the range reflect a transient lag period resulting from yet-insufficient exhumation to remove the inherited pre-rift cratonic thermal structure. This non-steady state condition of rapid uplift outpacing erosion has resulted in preservation of relict landsurfaces, truncated spurs, hanging valleys, uplifted river terraces, and vast stranded bogs at high elevation. Given the low cooling rate and geothermal gradient prior to rifting implied by U-Pb thermochronometry we determine that no more than 1.7 km of erosion could have accompanied uplift on the order of at least 5 km in the Rwenzori region. Biostratigraphic evidence suggests the range rose from beneath local baselevel within the last 2.5 Ma. This requires a minimum average uplift rate of 1.6 km/Myr. Regardless of the active rock uplift rate of the Rwenzori, net exhumation cannot yet have exceeded the depth of the (U-Th)/He closure isotherm in apatite (<1.7 km). These results highlight the danger of modeling young orogenic systems using the simplifying assumption of topographic steady state. / by Daniel MacPhee. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1984. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 233-238. / by Jane Hsiung Wojcik. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, June 2002. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Pages 460-462 blank. / Includes bibliographical references. / Three extensional fault systems intersect in the central Nepal Himalaya: the South Tibetan fault system (STFS); the Thakkhola graben; and structures bounding the Upper Mustang Massif (UMM). Interactions between these systems are investigated using integrated field studies, remote sensing analyses, geodynamic modeling, and a wide variety of geochronologic tools. The goals are to characterize the relationships between the three extensional systems, document their neotectonic histories in relation to their older manifestations, and develop a model for how the geodynamic phenomena driving them have produced the observed patterns of tectonism and deformation. 14C geochronology, remote sensing analyses, and field observations in the southern Thakkhola graben show that the STFS has been active in the Quaternary and that the kinematically-linked Thakkhola graben acts as a tear structure in its hanging wall. In the northern Thakkhola graben, neotectonic, structural, and 40Ar/39Ar and U-Pb geochronologic data from the UMM record its Late Miocene to Quaternary exhumational history and reveal a kinematic and geometric relationship between core-complex extension in the UMM and rift extension in the Thakkhola graben. / This work shows that core-complex development and east-west extension in southern Tibet are closely related to the STFS. In the adjacent Dhaulagiri Himalaya, remote sensing and field analyses of several generations of STFS structures - some of which appear to be active - show that the most recently active fault traces do not necessarily follow pre-existing lithologic contacts defined by older strands, but instead follow less contorted traces, cutting across allochtons and even reactivating segments of the Main Central Thrust. The distribution of high-grade rocks and the interactions between the STFS, east-west extension, and core-complex development are hypothesized to reflect the response of the orogen to gravitational potential energy (GPE) anomalies. GPE anomalies in the Himalaya are calculated from geoid data and interpreted in terms of pressure gradients driving flow in an intracrustal channel. From the distribution of GPE anomalies, I suggest that orogen parallel flow may be as significant as orogen-perpendicular flow, indicating that both removal and redistribution of GPE is important in the development of extensional structures in the Himalayan orogen and in southern Tibet. / by José Miguel Hurtado, Jr. / Contents of CDROM: Standard Adobe PDF files of the disserataion -- PDF compatible (Adobe Illustrator) files of the official defense notices -- Microsoft Powerpoint presentation used during the defense talk -- Apple Quicktime animation of the Powerpoint slides -- Standard Adobe PDF of the author's CV. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2007. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 40-41). / Scientists at NASA's Goddard Space Flight Center have developed a Combined X-ray Diffraction/Fluorescence (CXRDF) instrument. CXRDF performs simultaneous chemical and structural analysis of an unprepared sample, making it ideal for planetary mineral identification. In an effort to analyze the effectiveness of CXRDF, samples were chosen from a list of minerals that are important in the debate about the origin of the outcrops at Meridiani Planum on Mars. These samples were run on both CXRDF and a laboratory X-ray diffractometer. The datasets were compared, looking at peak identification, d-spacing resolution, and whether the instruments could definitively identify each sample. CXRDF successfully measured the d-spacings for each mineral, and the chemical analysis data were very valuable. However, for CXRDF to be able to definitively identify minerals, its d-spacing range and resolution will need to be improved, in addition to its data analysis software. / by Caitlin A. Murphy. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Includes bibliographical references. / by Karen Susan Bartels. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (p. 146-154). / by Elise Ann Ralph. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 101-104). / We developed a (almost) fully automatic earthquake detection and location method to study seismicity on regional scales based on array-processing techniques. We combined the beam-formed network response with template matched-filtering to enhance detection capabilities. We applied our method to the study of the seismicity of the Western Alps, and we claim that it can be applied in many different contexts to quickly get high quality earthquake catalogs. The study of the seismicity of the Western Alps revealed continuous seismic activity, organized into background and strongly clustered seismicity. We detected 9,018 seismic events from August 2012 to August 2013, outperforming the reference catalog that accounts for 1,698 events in the same period. Comparisons between our catalog and reference catalogs/ studies show that we retrieve well the main features of the region. We also studied source parameter differences between background seismicity earthquakes and clustered seismicity earthquakes. Using spectral ratios of collocated events, we measured the seismic moments Mo and corner frequencies f, for earthquakes detected with a subset of 11 template events. We found that background seismicity earthquakes follow the scaling law ... usually associated with self-similar earthquakes, whereas clustered earthquakes strongly deviate from this scaling law. Our observations show that the corner frequencies exhibit little dependency on the seismic moments, following a scaling law around ... We conclude that, in our study region, the degree of clustering seems to be driven by the rupture mechanism. / by Eric Beaucé. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references. / A high resolution stratigraphic study of the Terminal Proterozoic (ca 549 Ma) Hoogland Member of the Kuibis Subgroup, Nama Group, Namibia, revealed the controls on overall carbonate ramp platform morphology in a storm-dominated foreland basin setting. It was found that a generalized suite or class of physical processes that act to restore the seafloor to a relatively flat state by sweeping sediment from the highs and deposit in the lows does not allow for the continued inheritance and propagation of relief between sedimentary "elements" (e.g. laminae, bed, bedset) or larger scale "entities" (e.g. parasequences, systems tracts, depositional sequences). This damping of topographic elements on the seafloor was found to act at a variety of temporal and spatial scales from the sub-annual and sub-meter laminae and facies scale, through the Milankovitch band and meter-scale of parasequences up to the millions of years and scores to hundreds of meters of a depositional sequence. At the meter-scale, bioherms at the base of the studied stratigraphic interval are shown to have been covered and smothered by heterolithic interbeds of shale and fine grained carbonate mud-dominated facies. Facies-scale microbial laminites are shown to posses paleogeographic dip position-dependent centimeter-scale roughness elements that increase in roughness downdip. Relief produced along the tops of laminae is damped out by an overlying sediment rich layer suspended by storms or produced as whitings in the water collumn. Lateral extents of carbonate capped parasequences were found to vary as a function of position within a systems tract or genetic (accomodation) cycle. Late transgressive parasequences are found to be more extensive than those deposited during early transgressive and late highstand conditions due to the presence of basinward thickening shale wedges at their bases. This accommodation space-filling shale acted to decrease the slopes on the platform and allowed the influence of storm wave and current induced seabottom shear stresses to act over a greater area. The presence of a basinward accommodation-filling sediment source evidenced in the basal shale wedges of this foreland basin setting precluded the development of a steep sided rimmed shelf edge. A self-reinforcing ramp profile was maintained despite the fact that thrombolitic and stromatolitic reef forming organisms and processes were present. / by Steven P. DiBenedetto. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Includes bibliographical references (p. 203-222). / by Kurt Lewis Feigl. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 40-46). / The Maria Fold and Thrust Belt (MFTB) and Colorado River Extensional Corridor (CREC) were the sites of atypically extreme compression in Mesozoic time and extension in Cenozoic time, respectively. The orientations of these deformational structures are at odds with the Sevier and Laramide thrust belts and the Basin and Range Extensional Province surrounding these areas, a fact that remains largely unexplained. Data pertaining to metamorphic grade, deformational structures, and plutonism are compiled and reported in order to characterize compression and metamorphism. Field data on the 18.6 Ma Peach Spring Tuff are collected and presented and data on cooling ages are compiled in order to characterize extension. It is suggested that high metamorphic temperatures and ductile compressional structures are related to Late Cretaceous S-type plutonism; furthermore, it is suggested that later extension is related to earlier metamorphism and compression. It is demonstrated that the spread in attitudes of the Peach Spring Tuff correlates well with the degree of post- 18.6 Ma extension. Finally, a favored model is presented for the Mesozoic-Cenozoic evolution of the MFTB and CREC. / by James R. Pershken. / S.B.