Abstract: The Effect of Global Cyclostratigraphy on Sequence Stratigraphic Interpretation

Martin A. Perlmutter, Barbara Radovich, Martin D. Matthews

Although the concepts of sequence stratigraphy recognize sediment flux as an important variable, time invariant sediment supply is commonly assumed during application of idealized sequence stratigraphic models. Consequently, the primary driving force for stratigraphic variability is assumed to be dip directed shift of depositional environments and change in accommodation space caused by the relative rise and fall of sea level and tectonic subsidence. In sequence stratigraphy, sequences are subdivided into systems tracts representing genetically linked strata interpreted to be deposited at different phases of sea or lake level. Reservoir, seal and source rock occurrences are associated with systems tracts and their inherent timing with respect to sea level. This approach focuses the se smic interpreter on geometric changes in accommodation space with time. In doing so however, the intrinsic variability of the lithology caused by cyclic changes in the sediment supplied to the depositional basin is neglected. This may cause misdiagnosis of the distribution of lithologies within systems tracts and, therefore, the projection of geologic risk associated with exploration.

By incorporating global cyclostratigraphy, the internal stratal architecture of systems tracts can be determined at a finer resolution than allowed by sequence stratigraphy alone. Simulation of stratigraphy using the computer program Sedpak illustrates this point. Modeling clearly demonstrates lithologic variation is dependent on climate and the phase relationship of the sediment supply cycle to sea or lake level cycles. This phase relationship is a function of climatic succession and is directly associated with paleogeography.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994