In contrast to early work establishing the importance of earthquake-induced liquefaction in producing soft-sediment deformation (SSD) of the Navajo Sandstone, this report advances the use of SSD analysis to: characterize wet climatic conditions and flood events during the depositional history of ancient eolianites; discriminate the signatures of multiple deformation events from those of complex deformation features formed in a single event; and to document the occurrence of liquefaction features unrepresented in modern Earth analogues. The diversity of deformation styles, presented here, is very unusual in a report from a single formation; yet the high resolution of interpreted time relationships between various processes of deposition, erosion, water table fluctuation, and deformation is even more notable. These exceptional features derive from the extraordinary outcrops of the Colorado Plateau, which expose many large-scale (tens of meters) features throughout their entire extent and reveal an extended history of episodic deformation through thick (hundreds of meters) sections of cross-bedded units, which frequently continue along several kilometers of cliff face.
Prior studies of fluid escape from unconsolidated sand that support the present work are outlined in Chapter II. These include laboratory simulations of liquefaction and fluidization as well as analyses of analogous deposits, both ancient and modern. Chapter III provides an overview of outcrop evidence, gathered during the course of this study, for dramatic alterations in the topography and sedimentation patterns of the Navajo erg. Interpreted perturbations include: the foundering of active dunes; sediment eruptions; and the subsidence of interdune surfaces. Chapter IV constitutes an example of the detailed analyses that support the overview of Chapter III. Outcrop features from a site in West Canyon, Arizona provide the basis for interpreting the subsidence of a dry interdune surface to a position several meters below the contemporary water table, followed by the filling of this depression with a succession of mass flow, lacustrine, and eolian deposits. Chapter V outlines the implications of various outcrop features for the prevailing model of soft-sediment deformation in the Navajo Sandstone. Proposed modifications of this model accommodate a broader range of deformation dynamics and specifically incorporate the impact of wet climates.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/31699 |
| Date | 05 January 2012 |
| Creators | Bryant, Gerald |
| Contributors | Miall, Andrew |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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