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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Research
Vol. 74 (2004), No. 2. (March), Pages 203-220

Three-Dimensional Numerical Modeling of Deltaic Depositional Sequences 1: Influence of the Rate and Magnitude of Previous HitSeaNext Hit-Previous HitLevelNext Hit Change

Bryan D. Ritchie*, Rob L. Gawthorpe, Stuart Hardy**

ABSTRACT

A three-dimensional numerical model of deltaic deposition is used to investigate the influence of Previous HitseaNext Hit-Previous HitlevelNext Hit changes on delta development and sequence variability. Results illustrate the three-dimensional morphology of key stratal surfaces and architecture of stratal units (Previous HitsystemsNext Hit Previous HittractsNext Hit) and highlight the importance of the rate and magnitude of Previous HitseaNext Hit-Previous HitlevelNext Hit change in controlling the evolution of deltaic depositional sequences. High rates of Previous HitseaNext Hit-Previous HitlevelNext Hit fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate, finger-like forced regressive lobes separated by large areas of nondeposition. In contrast, low rates of Previous HitseaNext Hit-Previous HitlevelNext Hit fall cause only minor channel incision, which occurs late during Previous HitseaNext Hit-Previous HitlevelNext Hit fall. As a result, sediment is supplied more uniformly to the delta front, leading to an attached, laterally continuous forced regressive apron. During lowstand and subsequent Previous HitseaNext Hit-Previous HitlevelNext Hit rise, the delta morphology and internal geometry are strongly controlled by the rate of rise. High rates lead to: i) poorly developed lowstand wedges that are drowned early, ii) high-magnitude transgressions, and iii) the late development of maximum flooding surfaces. The stratigraphy developed during Previous HitseaNext Hit-Previous HitlevelNext Hit rise is also strongly influenced by the incised-valley system created during the preceding Previous HitseaNext Hit-Previous HitlevelNext Hit fall. If deep, major valleys developed that captured most of the sediment supply, the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during Previous HitseaNext Hit-Previous HitlevelNext Hit rise. Even within a single delta, Previous HitsystemsNext Hit Previous HittractsTop and key stratal surfaces show three-dimensional variability and two-dimensional sections often lack significant elements of the stratigraphy. As a result, analysis of two-dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes.


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