Virtual Field Trip: Alpine Fault
Thrust section at Gaunt Creek
The Alpine Fault in the central region forms dipping sections with oblique thrust characteristics connected by sections with mainly dextral strike-slip, resulting in a "zigzag" outcrop pattern. In this view looking south across Gaunt Creek, the Alpine Fault is seen emplacing mylonite over Holocene gravels. The light-coloured material is the basal cataclasites (crushed mylonite), here some 40 m thick. The fault dips c.35 degrees SE near the base of the outcrop although it flattens to the west as it reachs the original ground surface.
In the diagram of the Gaunt Creek outcrop:. The overthrust gravels form a sequence of river deposits and talus fans and are dated between 13,000 and 10,000 yr BP. Taking into account the oblique slip direction, slip rate on the fault is calculated as at least 18-24 mm/yr.
Cooper, A. F. and Norris, R. J., 1994