Topset Play Types and Their Controls
N. J. Milton, G. T. Bertram, 1995. "Topset Play Types and Their Controls", Sequence Stratigraphy of Foreland Basin Deposits: Outcrop and Subsurface Examples from the Cretaceous of North America, J.C. Van Wagoner, G.T. Bertram
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Cycles of progradation and retrogradation of a basin-margin system of topsets and clinoforms are controlled by the balance between sediment supply rate and the rate of creation of topset accommodation volume. The latter is defined as the product of the topset area and the rate of rise of relative sea level. If the system is graded,with sand preferentially trapped in the proximal part of the system, i.e., the topsets, then the topset sand percentage is controlled by the rate of sand supply and the rate of creation of topset accommodation volume. The topsets of systems tracts with a high topset volume will be relatively less sandy than those with a low topset volume, and topset sand percentage will vary in a systematic manner within a sequence.
The play types associated with the topsets are strongly influenced by the relative abundance in the topsets of reservoir and seal. Different types of basins are characterized by different topset play types.