Abstract: Stratigraphic Modelling of Alluvial Fans Including Hydrodynamics, Tectonics, and Transport Laws

Pascal Allemand, Gilles Dromart

The parameters that control depositional architectures are the following:

(1) sediment supply related to tectonic and climatic conditions in nearby landscapes

(2) hydrodynamics that distributes sediments into accommodation space

(3) tectonics that controls accommodation spaces and depositional profiles

(4) transport laws that determine location of erosion, by-pass and deposition.

Each parameter has a feed-back effect upon other parameters. Any model aimed at understanding depositional architectures should be based on physic laws of hydrodynamics, tectonics, and transport, and should include coupling of these laws.

Current models, either diffusive or geometric, do not integrate physics of processes. Even the models are somewhat predictive, they do not really explain the roles and interactions of the parameters.

The proposed modelling solves together low Reynolds number Navier-Stokes Equations and equilibrium equations of an extensional wedge. The case of alluvial fans entering into a lacustrine system has been processed. The following points have been specifically addressed:

(1) How does such a depositional system respond to a disequilibrium caused by any change in the sediment supply, lake-level, and regional stress-field?

(2) does the stratigraphic record reflect steady states?

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France