Presentation Title

Analysis of Deformation Bands at Slim Buttes, SD

Advisor Information

Harmon Maher

Location

Dr. C.C. and Mabel L. Criss Library

Presentation Type

Poster

Start Date

3-3-2017 12:30 PM

End Date

3-3-2017 1:45 AM

Abstract

Deformation bands are mm-thick zones of localized strain that occur in porous sandstones and sediments. Grain reorganization must occur in order for deformation bands to form; therefore, the host rock must be porous enough for movement to occur. The primary classification system for these structures is based on kinematics and breaks them down into three categories. They are not fully understood, influence local hydrology and are, therefore, a topic of active research in the field.

This research was done on deformation bands at Slim Buttes in northwest South Dakota. These bands exhibit multiple unusual characteristics, including consistent spacing and complex orientation distributions. A primary question behind this research is how the deformation bands relate to the faults in the area and whether or not there is a preferred orientation. Additionally, through thin section analysis, we hope to classify what type of deformation bands these are.

Systematic measurements of the deformation bands were taken in the field and then used to create orientation plots. The plots showed significant dispersion, but also four strong preferred orientations along the fault: a conjugate pair of sets aligned with the fault, a set perpendicular to the fault, and a set strike parallel to the fault. This could provide evidence into how the stress field evolved during deformation. The thin sections show a reduction in porosity and evident grain reorganization, indicating these deformation bands are compactional shear bands. Future work will focus on why these deformation bands differ from those described in the geologic literature.

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COinS
 
Mar 3rd, 12:30 PM Mar 3rd, 1:45 AM

Analysis of Deformation Bands at Slim Buttes, SD

Dr. C.C. and Mabel L. Criss Library

Deformation bands are mm-thick zones of localized strain that occur in porous sandstones and sediments. Grain reorganization must occur in order for deformation bands to form; therefore, the host rock must be porous enough for movement to occur. The primary classification system for these structures is based on kinematics and breaks them down into three categories. They are not fully understood, influence local hydrology and are, therefore, a topic of active research in the field.

This research was done on deformation bands at Slim Buttes in northwest South Dakota. These bands exhibit multiple unusual characteristics, including consistent spacing and complex orientation distributions. A primary question behind this research is how the deformation bands relate to the faults in the area and whether or not there is a preferred orientation. Additionally, through thin section analysis, we hope to classify what type of deformation bands these are.

Systematic measurements of the deformation bands were taken in the field and then used to create orientation plots. The plots showed significant dispersion, but also four strong preferred orientations along the fault: a conjugate pair of sets aligned with the fault, a set perpendicular to the fault, and a set strike parallel to the fault. This could provide evidence into how the stress field evolved during deformation. The thin sections show a reduction in porosity and evident grain reorganization, indicating these deformation bands are compactional shear bands. Future work will focus on why these deformation bands differ from those described in the geologic literature.