AN ANALYSIS OF DEFORMATION BAND POROSITY IN SANDSTONES AND CONGLOMERATES

We studied the various properties of deformation bands in porous sandstone and conglomerate lenses in the Wahweap Formation near Bryce Canyon. Although it is well known that deformation bands reduce the porosity and permeability in porous sandstones, a literature review did not reveal significant information regarding how porosity and permeability differ between deformation bands occurring in sandstone from those occurring in conglomerate. It is somewhat rare to find deformation bands in sandstone layers with conglomerate lenses where the stress was sufficient to cause deformation bands to propagate through both lithologies. The Hillsdale Canyon area near Bryce Canyon is an excellent opportunity to study this rare occurrence. Thin sections from five samples of sandstone and five samples of conglomerate were prepared and analyzed under a microscope to determine porosity and other structural attributes. The image analyst tool, JMicrovision, was also tested on the thin sections to determine its effectiveness in analysis compared to manual point counting. Understanding the differences in porosity and permeability of deformation bands in various lithologies could help sedimentary petrologists to more accurately predict characteristics of reservoirs in rock layers known to have deformed sandstone and conglomerate lenses.