Climatic/eustatic cycles of the Plio-Pleistocene have been defined in the northern Gulf of Mexico and precisely tied to their associated sequences and lithologies by means of graphic correlation. This framework has provided the data necessary for a detailed empirical evaluation of the eustatic depositional systems tract models. The key to this evaluation is a eustatic sea level curve derived from fossil and isotope data. A curve of this type has been defined for several sequences. Using this eustatic curve the actual lithofacies and position of the various systems tracts were directly compared to those predicted by the models.

The evaluation of the data with respect to eustatic sea level yielded conclusions that are significantly different from those predicted by the model. The most significant of these differences are: 1) significant amounts of sand were deposited in deep water during transgressive and highstand intervals, 2) the observed vertical succession of eustatic depositional systems tracts within a given sequence are transgressive, highstand and lowstand, 3) factors other than eustasy have been the dominant influence on facies distribution within the Plio-Pleistocene sequences studied.

These results demonstrate that depositional systems tracts and internal facies distribution could not be adequately described by a single model. Therefore, sequence stratigraphic analysis should be empirically based and conducted within the context of the basin, instead of being model-driven.

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