Stratal architecture in a prograding shoreface deposit, eastern shore, VA: Relationship to grain size, permeability, and facies distribution

A fundamental concern of the stratigrapher is to develop predictive models of stratigraphic organization. In sedimentology one of the most significant problems that has yet to be resolved is the fact that there is a lack of quantitative information regarding the relationship between geometry of beds, thickness of beds, grain size and sedimentary structures in sandy environments, especially shallow marine deposits. Scientists have also realized the need to correlate quantitative permeability to sedimentary structures and scales of stratigraphic organization. The purpose of the study is to investigate the scales of stratigraphic organization that control the variation of grain size and permeability in shallow marine deposits. A model of stratal architecture is constructed in order to relate scales of stratigraphic organization to these properties. The hypothesis tested is that models of stratal architecture are more efficient predictors of grain size and permeability than are facies models in shallow marine sands. Several methods are used to test the hypothesis, including mapping of stratal geometry, measuring stratal characteristics, and the construction of facies distribution through measured sections. These techniques are used to erect the stratal architecture of strand plain deposits at Oyster, Virginia. ANOVA, Tukey-Kramer Means Comparisons tests and variograms are performed to test the statistical significance of mean grain size and permeability variability over multiple scales of stratigraphic organization. Results from this study demonstrate that multiple levels of stratigraphic organization are statistically significant with respect to the spatial variability of grain size and permeability, and that one-dimensional facies models are clearly unable to resolve these important stratigraphic scales. The study also revealed that a parabolic relationship exists between mean grain size and set thickness, and is thought to be the evolutionary consequence of the progressive sorting process.