Sedimentary Dynamics and Biostratinomy of a Middle Cambrian Rusophycus Lagerstätte, Gros Ventre Formation, Wyoming, USA

Aquifer heterogeneity at small scales (meters to tens of meters) can be characterized with hydrofacies. We investigate the feasibility of translating lithofacies into hydrofacies by testing the hypothesis that the permeability frequency distributions of different lithofacies are distinct. We mapped 11 lithofacies and performed more than 1800 in situ permeability measurements at an outcrop exposing poorly cemented, nonmarine, clastic sediment. The lithofacies represent both channel and interchannel deposits, are both ribbon-form and tabular, and vary in grain size from clay to sandy gravel. For each lithofacies permeability sample, we calculated variograms to define correlation lengths that were used to select spatially uncorrelated subsamples from each sample. The frequency distributions of permeability subsamples from the various lithofacies were compared using nonparametric statistical tests. The statistical tests generally support the claim that the lithofacies permeability distributions are distinct from one another.