Dissertation/Thesis Abstract

High-resolution architectural evolution of depositional elements in deep-marine slope environments: The Quaternary Niger Delta slope, Quaternary southwest Grand Banks slope, Canada, and Cretaceous Tres Pasos Formation, Chile
by Armitage, Dominic Anthony, Ph.D., Stanford University, 2009, 166; 3351485
Abstract (Summary)

This thesis advances knowledge and understanding of the sedimentology of deep-water continental slopes by providing a comprehensive, multi-scale analysis of the evolution of slope deposits through time. Continental slopes are complex environments, which are inherently depositionally heterogeneous. Recent technological advances in remote sensing and direct sediment sampling techniques have resulted in numerous detailed studies of slope sediments. However, previous investigations rarely bridge the gap between deep-penetration seismic-reflection surveys and ultra high-resolution seafloor studies. The four chapters of this thesis present new data at multiple resolutions on the detailed evolution, distribution, and stratigraphic architecture of deep-water slope deposits in order to better understand specific sedimentation processes. Direct observation and sampling of deep-water sediment gravity flows is difficult due to their low recurrence interval and destructive nature; therefore, inferences of processes are commonly made from sediment-gravity flow deposits, experiments, and models. Such inferences lead to a variety of interpretations, resulting in the need to integrate datasets at multiple resolutions in an attempt to generate more precise conclusions. In order to address this issue, this study incorporates bed-scale characterization and subsequent forward-seismic modeling of outcrops in Chile, interpretation of high-resolution 3D seismic-reflection data from Nigeria, and ultra high-resolution 2D and 3D seismic-reflection data with analysis of seafloor sediment cores from Canada.

Chapter 1 is a 3D seismic-reflection based study of channel systems on the seafloor and in the shallow subsurface of the Niger Delta continental slope. The objectives were to document the chronology of channel avulsions and the evolution of channel-fill through time, in order to better understand how, why, and where submarine channels avulse.

Chapter 2 presents results of a multi-scale analysis of the stratigraphic architecture of sedimentary deposits on the southwest Grand Banks of Newfoundland, Canada.

The slope in the study area is deeply dissected by canyons and partitioned by steep, narrow ridges. The latter are common features of glacially influenced margins, but their mode of formation is not well understood. An objective of this study was to identify the predominant sedimentary processes responsible for the depositional geometries and the facies observed on this part of the continental margin, and the mechanisms responsible for creating those processes. Results from this study can be applied to other glacially influenced margins to explain the formation of similar features.

Chapter 3 is a detailed outcrop study of the depositional architecture of the Cretaceous Tres Pasos Formation of the Ultima Esperanza District, Chile. The primary goal of this study was to document the influence of the mass-transport deposits (MTDs) on the subsequent evolution of the sandstone architecture. A model of MTD surface topography, delineating the different scales observed at the outcrop, is presented in this chapter and can be applied to analogous MTD-dominated deep-water slope environments, from relatively high-resolution ancient outcrops to lower-resolution seismic-reflection-based studies.

Chapter 4 complements chapter 3 and presents a synthetic seismic-reflection model of the Sierra Contreras, which serves as a useful analogue to similar depositional environments in the subsurface. The purpose of this chapter is to demonstrate effective application of outcrop studies to the interpretation of subsurface seismic-reflection data. A precise lithological model was created from the outcrop observations presented in chapter 3, from which synthetic seismic-reflection profiles were generated at various resolutions. (Abstract shortened by UMI.)

Indexing (document details)
Advisor: Graham, Stephan A.
School: Stanford University
School Location: United States -- California
Source: DAI-B 70/03, Dissertation Abstracts International
Subjects: Geology, Physical oceanography
Keywords: Continental slopes, Grand Banks, Mass-transport deposits, Niger Delta, Submarine fans, Tres Pasos Formation, Turbidites
Publication Number: 3351485
ISBN: 9781109077216
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