--> Abstract: Forcing Mechanisms in Sequence Stratigraphy and the use of Simple Large-Scale Forward Numerical Models; #90063 (2007)

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Forcing Mechanisms in Sequence Stratigraphy and the use of Simple Large-Scale Forward Numerical Models

 

Geslin, Jeffrey1 (1) ExxonMobil Exploration Company, Houston, TX

 

The interrelated forcing mechanisms of climate, tectonics and eustasy control accommodation generation and sediment supply rates that produce sequence stratigraphic architectures. The relative dominance of one mechanism at a given location along a depositional profile controls stratigraphic architectures at subregional to regional scales. Cyclic changes in forcing mechanisms produce cyclic changes in accommodation generation rate (A) and sediment supply rate (S). The ratio of rate of change of accommodation generation rate (dA/dt) and rate of change of sediment supply rate (dS/dt) controls generation of progradational, aggradational and retrogradational stacking, as well as sequence boundaries and flooding surfaces. Understand the distribution and cyclicity of dominant forcing mechanisms along a depositional profile is crucial to successfully building large-scale forward numerical models that predict lateral and vertical stratal continuity and variability.

 

Simple large-scale forward numerical models were used to investigate the effects of climatic and eustatic cyclicity on a fluvial depositional profile where aggradation or degradation of the landscape is controlled by changes in the equilibrium profile of the stream. These finite difference pseudo-2D models demonstrate several sequence stratigraphic concepts. 1) Eustatically generated sequence boundaries extend only a relatively short distance updip of the shoreline (100-150 km) within the models, dependent upon the degree to which dA/dt / dS/dt << 1. 2) Sequence boundary formation in down-dip areas is dependent upon both baselevel fall and stream power available to erode. 3) Climatic sequence boundaries that form updip of areas affected by eustasy can be spatially and temporally unrelated to down-dip eustatic sequence boundaries.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California