HARDY, STUART, and DAVE WALTHAM, Fault Dynamics, Department of Geology, Royal Holloway, University of London, Egham, Surrey

ABSTRACT: Numerical Modelling of Tectonics, Eustasy and Sedimentation

Using a general forward modelling equation the effects of tectonics, eustasy and sediment flux on clastic and carbonate geometries and facies are investigated. The modelling approach allows the integration of regional and local tetonic effects, eustatic sea level change and variations in sediment flux through time. Model results are presented as conventional geometric diagrams and also in terms of pseudo-facies. Dependent

upon the environment being modelled pseudo-facies are based upon the original depth and dip of deposition, grain-size distribution, accumulation rate or dominant process of deposition.

The ability of the modelling approach to model geometries and facies in a variety of settings is assessed. Sediment geometries and facies developed in domino fault block systems, fault-controlled fan-deltas, large deltaic systems, carbonate platforms and in the region of growing salt pillows are modelled. The modelling shows that tectonics, eustasy and sediment flux can all exert a strong control on sequence architectures and facies patterns. In each of these settings chronostratigraphic information, eustatic sea level curves and rates of tectonic and sedimentary processes can be used to constrain the probable causes of sequence geometries.

The modelling approach leads to fast and robust algorithms. By varying tectonics, eustasy and sediment supply (and their inter-relationships) one can quickly test alternative hypotheses explaining the development of sequence stratigraphic and facies relationships.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.