Muto, Tetsuji1, Ron Steel2
(1) Nagasaki University, Nagasaki, Japan
(2) The University of Texas at Austin, Austin, TX
ABSTRACT: Principles of Autostratigraphic Analysis: Implications from Flume Experiments
Autostratigraphy is the stratigraphic product of autogenic processes in depositional systems where the systems respond to steady forcing of basins or constant dynamic conditions (e.g., sea-level rise at constant rate). Autostratigraphy provides an initial analytical tool to explain or predict sediment-stacking patterns in data sets, before allocyclic controls are invoked, and thus can act as a framework 'norm' of genetic stratigraphy. Any conventional sequence stratigraphic analysis should be preceded by autostratigraphic analysis and allocyclic changes should only be introduced as absolutely necessary. Laboratory experiment under controlled conditions allows us to explore autogenic processes and resulting sediment-stacking patterns. Because combined steady and unsteady dynamic forcing is likely to be common in natural environments, purely autostratigraphic successions will be uncommon in the geological records. We present several examples of autostratigraphic successions, produced by fluvial deltas in flume experiments with different patterns of sea-level cycles. In terms of the inverse problem, autostratigraphic analysis is applied to experimental successions to demonstrate how it is possible to enhance and revise conventional sequenced stratigraphic interpretations. A key point is that unsteady forcing of basins can be detected by paying attention to temporal changes in the characteristic length scales in a considered deltaic system, where the rate of sediment supply and the rate of sea-level change are specified.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.