The northeastern portion of the clarence fault: Tectonic implications for the late neogene evolution of marlborough, New Zealand

Abstract

The Clarence Fault does not extend northeastward to the Marlborough coast as traditionally mapped. Instead, it joins with a northerly trending shear zone within the Torlesse Supergroup near Peggioh Station, 10 km west of Ward. In this region the Clarence Fault is a blind, west‐dipping moderate‐angle reverse or thrust fault, east of which, on the downthrown side, the Late Cretaceous and Tertiary sedimentary and volcanic succession has been overturned. The Clarence Fault and a number of associated splay faults represent a positive flower structure that formed in association with drape folding. These structures probably began forming in the early Miocene. If the present‐day rate of dextral strike‐slip on the Clarence Fault of 4–8 mm/yr were extrapolated into the past, the total inferred lateral offset of 15 km along the fault could be accomplished in 3 million years. Consequently, it is suggested that the Clarence Fault has acted as a dextral strike‐slip structure only comparatively recently, in the order of the last few million years, and that before this it was a southward‐directed thrust fault. © The Royal Society of New Zealand 1992.