Geometry, Microstructure and Petrophysical Properties of Compaction and Shear Bands at Silica Dome, Valley of Fire State

We characterized and compared shear and compaction bands formed in Aztec Sandstone in Silica Dome, Valley of Fire, Nevada, USA. We investigated various portions of a single sand dune (from bottom-sets to fore-sets), and documented multiple sets of compaction bands and shear bands. We have conducted geometric (length and thickness) and in-situ measurements of permeability and hardness of compaction and shear bands and the surrounding host rock. Microstructural analysis has been performed on thin sections of representative samples to understand and compare the characteristics of shear and compaction bands. Our results confirm that shear bands are longer and thinner than compaction bands in this locality. Density, elastic moduli and permeability of shear bands have a wider range than those of compaction bands. This reflects the heterogeneous microstructures, which relates to different degrees of compaction and cataclasis along the shear bands. Shear bands can reduce porosity and permeability more than compaction bands (in extreme cases), up to two orders of magnitude compared to host rock in this study.