James R. P. Owens¹, Stuart Hardy², David W. Hunt³
(1) Manchester University, Manchester, United Kingdom
(2) The University of Manchester, Manchester, United Kingdom
(3) University of Manchester, Manchester, United Kingdom

Abstract: Assessing the role of antecedent topography, tectonism and eustasy on isolated platform development: insights from three-dimensional modelling

A three-dimensional numerical model of carbonate production and deposition is used to investigate the effects of antecedent topography, tectonic subsidence, eustasy and oceanic setting on the development of land-mass detached carbonate platforms. The model incorporates fully three-dimensional depth and facies dependent carbonate growth together with slope failure and windward-leeward influenced sediment redistribution. A search algorithm based on open-marine connectivity enables the identification of lagoonal/restricted, open-marine, reefal and subaerial facies tracts. A closely spaced 2D seismic grid from an Oligo-Miocene isolated platform from offshore Vietnam has been used to define 3D initial surfaces for the model and biostratigraphic data from two platform penetrating wells provide a chronostratigraphic framework enabling the derivation of appropriate rates.

Comparison of model results to seismic sections highlights the influence of antecedent topography on the spatial distribution of by-pass and accretionary margins. Overall platform asymmetry appears to develop as a result of the combined effects of topographic relief and eustatic sea-level variation rather than the more commonly cited unidirectional windward to leeward energy flux. Small scale pinnacle buildups clearly identified on seismic are predicted to occur by the model in comparable locations: on subtle tectonic highs and platform margins. Sensitivity studies indicate that it is difficult to generate such architectures on simple planar surfaces in the absence of inherent topographic variability. The ability to incorporate seismically defined depth converted surfaces into the 3D numerical model has proved useful in understanding the controls on isolated platform architecture and facies tract development.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana