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Full-Text Articles in Physical Sciences and Mathematics
Channel Width Response To Differential Uplift, Colin B. Amos, Douglas W. Burbank
Channel Width Response To Differential Uplift, Colin B. Amos, Douglas W. Burbank
Geology Faculty Publications
The role of channel width and slope adjustments to differential uplift in rivers within actively deforming terrains remains contentious. Here high‐resolution topographic surveying of formerly antecedent outwash channels demonstrates marked changes in channel width as a primary response to differential uplift. For five Late Quaternary alluvial paleochannels crossing small folds along the active Ostler fault zone of southern New Zealand, nearly continuous measurements of paleochannel width and concomitant incision reveal abrupt narrowing of widths toward minimum values at channel positions coincident with the initial uplift. When the magnitude of differential uplift is sufficiently small, narrowing alone permits these channels to …
Geomorphic Constraints On Listric Thrust Faulting: Implications For Active Deformation In The Mackenzie Basin, South Island, New Zealand, Colin Amos, Douglas W. Burbank, David C. Nobes, Stuart A. L. Read
Geomorphic Constraints On Listric Thrust Faulting: Implications For Active Deformation In The Mackenzie Basin, South Island, New Zealand, Colin Amos, Douglas W. Burbank, David C. Nobes, Stuart A. L. Read
Geology Faculty Publications
Deformed fluvial terraces preserved over active thrust-related folds record the kinematics of folding as fault slip accumulates on the underlying thrust. In the Mackenzie Basin of southern New Zealand, the kinematics revealed by folded fluvial terraces along the active Ostler and Irishman Creek fault zones are inconsistent with traditional models for thrust-related folding in which spatially uniform rock uplift typically occurs over planar fault ramps. Instead, warped and tilted terraces in the Mackenzie are characterized by broad, continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation. By relating this pattern of surface deformation to the underlying thrust …
Pleistocene Brawley And Ocotillo Formations: Evidence For Initial Strike-Slip Deformation Along The San Felipe And San Jacinto Fault Zones, Southern California, Stefan M. Kirby, Susanne U. Janecke, Rebecca J. Dorsey, Bernard A. Housen, Victoria E. Langenheim, Kristin A. Mcdougall, Alexander N. Steely
Pleistocene Brawley And Ocotillo Formations: Evidence For Initial Strike-Slip Deformation Along The San Felipe And San Jacinto Fault Zones, Southern California, Stefan M. Kirby, Susanne U. Janecke, Rebecca J. Dorsey, Bernard A. Housen, Victoria E. Langenheim, Kristin A. Mcdougall, Alexander N. Steely
Geology Faculty Publications
We examine the Pleistocene tectonic reorganization of the Pacific–North American plate boundary in the Salton Trough of southern California with an integrated approach that includes basin analysis, magnetostratigraphy, and geologic mapping of upper Pliocene to Pleistocene sedimentary rocks in the San Felipe Hills. These deposits preserve the earliest sedimentary record of movement on the San Felipe and San Jacinto fault zones that replaced and deactivated the late Cenozoic West Salton detachment fault. Sandstone and mudstone of the Brawley Formation accumulated between ∼1.1 and ∼0.6–0.5 Ma in a delta on the margin of an arid Pleistocene lake, which received sediment from …
Excess Silica In Omphacite And The Formation Of Free Silica In Eclogite, H. W. Day, Sean R. Mulcahy
Excess Silica In Omphacite And The Formation Of Free Silica In Eclogite, H. W. Day, Sean R. Mulcahy
Geology Faculty Publications
Silica lamellae in eclogitic clinopyroxene are widely interpreted as evidence of exsolution during decompression of eclogite. However, mechanisms other than exsolution might produce free silica, and the possible mechanisms depend in part on the nature and definition of excess silica. ‘Excess’ silica may occur in both stoichiometric and non-stoichiometric pyroxene. Although the issue has been debated, we show that all common definitions of excess silica in non-stoichiometric clinopyroxene are internally consistent, interchangeable, and therefore equivalent. The excess silica content of pyroxene is easily illustrated in a three-component, condensed composition space and may be plotted directly from a structural formula unit …
Precursory Seismicity Associated With Frequent, Large Ice Avalanches On Iliamna Volcano, Alaska, Usa, Jacqueline Caplan-Auerbach, Christian Huggel
Precursory Seismicity Associated With Frequent, Large Ice Avalanches On Iliamna Volcano, Alaska, Usa, Jacqueline Caplan-Auerbach, Christian Huggel
Geology Faculty Publications
Since 1994, at least six major (volume >106m3 ) ice and rock avalanches have occurred on Iliamna volcano, Alaska, USA. Each of the avalanches was preceded by up to 2 hours of seismicity believed to represent the initial stages of failure. Each seismic sequence begins with a series of repeating earthquakes thought to represent slip on an ice–rock interface, or between layers of ice. This stage is followed by a prolonged period of continuous ground-shaking that reflects constant slip accommodated by deformation at the glacier base. Finally the glacier fails in a large avalanche. Some of the events appear to …