Analytical and statistical approaches toward understanding sedimentation in siliciclastic depositional systems

Abstract

Recent studies of turbidite bed thickness distributions have demonstrated power law and other statistical distributions. Chapter 2 explores the different distributions which may express fan processes and may be used as a tool to classify environments. Chapter 3 illustrates a correlation between cumulative distributions of well known turbidite deposits and interpreted fan subenvironments. A power law distribution may be, for some systems, the primary input signal and a one dimensional model allows qualitative-quantitative characterization of the effects of different fan processes. Environments dominated by different fan processes may be characterized based on the degree to which processes have acted as a "filter", systematically modifying the assumed power law distribution. This model is used to help account for bed thickness distributions observed in several field sites. Turbidite sections are often characterized in terms of alternating packages of thinning- and thickening-upward intervals, which are interpreted to be representative of different subenvironments, including channel and levee environments. In Chapter 4, stratigraphic sections from several field sites are analyzed for dominance of asymmetrical bedding packages using runs analysis. Results indicate ( 1) a correlation between the number of beds in the dataset and the significance level of the results, with may relate to prevalence of progradational and lateral migration of deposits; (2) runs tests should be applied with caution to datasets containing significant levels of erosion and amalgamation; and (3) runs tests may be used to identify the presence of interlayered lithologies and perhaps flow types. In Chapter 5, the log-log cumulative distribution model and the runs test techniques are applied to turbidites of the Permian Skoorsteenberg Fonnation in the Tanqua-Karoo Basin, South Africa. Exceptional exposure permitted a number of lateral correlation studies over a range of scales. The cumulative distribution model is supported by the turbidite distributions broadly subdivided into fan and interfan environments. Runs analysis reveals that interfan environments are generally more ordered than fan environments. Chapter 6 illustrates the development of a dual-component heterogeneous sediment transport model. A grain-scale model is integrated with a large scale basin model to simulate transport and deposition of heterogeneous-sized sediment in a fluvial system.