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Book Chapter

Facies and Log Expression of Systems Tracts

January 01, 1999


The preceding chapter discussed the identification and interpretation of key stratigraphic surfaces. This aspect of a sequence stratigraphic analysis is an essential part of the general approach, but the analysis and interpretation of sediment stacking patterns between these surfaces is equally important. As discussed in Chapter 2, a sequence deposited during a cycle of change in relative sea level (or in fluvial accommodation) can be subdivided into systems tracts, characterized by specific stacking patterns and bounded by key stratigraphic surfaces. For reasons discussed in Chapter 2, we suggest abandonment of type 1 and type 2 sequence nomenclature, replacing it with a single sequence type. A complete sequence comprises three systems tracts: lowstand, transgressive, and highstand. Each systems tract represents a specific sedimentary response to the interaction between sediment flux, physiography, environmental energy, and changes in accommodation.

In practical terms, a systems tract consists of a sedimentary succession with a specific type of stacking pattern (i.e., regressive,stationary, or transgressive—in the case of coastal and shelfal deposits; Fig. 2.5). Systems tracts generally are deposited during a specific phase of relative sea level, though the precise timing of deposition of systems tracts is a function of the local balance between sediment flux and rate of change of accommodation. Within a sequence, the transgressive surfaces and maximum flooding surfaces described in Chapter 3 mark the physical boundaries between systems tracts, across which changes of stacking patterns can bk observed. A regressive or progradational stacking pattern consists of a succession of discrete stratigraphic

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SEPM Concepts in Sedimentology and Paleontology

Siliciclastic Sequence Stratigraphy—Concepts and Applications

Henry W. Posarnentier
Henry W. Posarnentier
ARC0 Exploration and Production Technology, 2300 West Plano Parkway, Plano, Texas 75075, USA
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George P. Allen
George P. Allen
Total Centre ScientiJique et Technique, Route de Versailles, 78470 Saint-R7èny-Iës-Chevreuse, France
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SEPM Society for Sedimentary Geology
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January 01, 1999




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