Date of Award
Master of Science (MS)
Petrographic study has been carried out on slickenside thin sections, to find out reliable microstructures for determining the slip-sense of faults, and to classify slickensides morphologically. Thin sections are made cut parallel to the striation and perpendicular to the slip plane. Many useful slip-sense indicators are found in thin section even though such indicators may be absent in hand specimens. They are (1) off-set or bending of once-continuous bodies such as veins, layers, grains or twin lamellae, (2) crystal fibers growing nearly parallel to the slip direction, (3) extensional fractures aligned oblique to the slip plane, (4) S-C geometries in ductile materials, and (5) Riedel- and P- shear fractures associated with the main slip surface.
Two distinct layers may exist adjacent to the slickenside surface. One is termed coating: a discrete layer of material immediately under the slip surface. The other is termed the deformed host layer which is a zone of deformation in the host rock developed parallel to the slickenside. Slickensides are classified into four morphological types depending on the presence or absence of coating and deformed host layers. They are type A (deformed host layer only), type B (coating and deformed host layer), type C (no coating and no deformed host layer), and type D (coating only).
This morphological classification can be a first step toward further genetic interpretation of slickensides, which could eventually be used to infer conditions of faulting. Possible development paths of each slickenside type indicate that present slickenside morphology can be influenced by rock type, slip-rate and depth of faulting during slip and by weathering and precipitation of veins along the pre-existing slip surface after slip. Although this classification is not yet fully satisfactory, it can perhaps be extended and improved by further systematic slickenside studies.
Lee, Young-Joon, "Slickenside petrography: slip-sense indicators and classification" (1991). Geology Theses and Dissertations. 52.