Autumn, of the year that we are in GLY 326 Structural Geology Lecture 31 Strike-slip Faults Gly 326 Autumn, of the year that we are in

Strike-slip faults: i.e. the movement parallels strike

Transform Plate Boundaries Where the motion of two plates is parallel to their boundary, lithosphere is neither created nor destroyed, but strain is concentrated, and shallow crustal seismicity is common

Strike-slip faults are classified depending on their relative movement as “left-” or “right-” lateral faults…

On a map, we mark the trace of the fault and (if is known) the relative movement

Strike-slip faults need not be perfectly planar and any irregularities in shape can cause other structures to form.

Strike slip fault bends The strike slip fault at left has a bend. What type of bend is it? What is the sense of displacement on the fault?

Strike slip Fault Bends Strike slip fault bends have two types: Releasing bends produce extensional structures: sags (basins) and normal faults Restraining bends produce shortening structures: uplifts, folds and thrust faults

Flower Structures positive: Palm Tree (transpression) negative: Tulip (transtension)

Faults often end in a “horsetail” structure, which can be transtensional (a- b) or transpressional (c-d)