Quantifying process-based controls on compensational stacking of channelized sedimentary deposits.

摘要

Inherent characteristics (autogenic behavior) of sedimentary systems are often thought to generate small-scale noise in the stratigraphic records and usually ignored in the stratigraphic interpretation. However, autogenic dynamics can also occur over large temporal and spatial scales and produce sedimentary records that mimic stratigraphic signals presumed to result from changes in external boundary conditions (allogenic forcings) such as tectonics, climate, eustatic change or a combination. As the autogenic fluctuations could impose first-order controls on stratigraphic architecture, it is necessary to search for quantitative methods in order to constrain river intrinsic behaviors and decode them from the complex stratigraphic responses by the scales over which autogenic stratigraphic patterns are most prevalent. The statistical metric we developed based on numerical modeling and physical experiments offers a good prediction on the autogenic time scales and results in a compensation index which can be used as an indicator for fluviodeltaic stratigraphic patterns. The magnitude of autogenic forcings presented in the fluvial successions is associated with the strength of channel-belt clustering and can be quantitatively classified by the compensation index. We utilize this index in conjunction with a serial of 2-D object-based stratigraphic stacking models, high-resolution experimental and field data to (1) quantify how the magnitude of autogenic processes varies with scales (2) understand how autogenic behaviors interact with river discharge and how this allogenic condition affects the stacking patterns of channel bodies (3) explore the mechanism by which surface topography and river kinetics influence the degree of stratigraphic organization in a net-aggradation system.