Abstract - The formation of the Taranaki Basin, an active volcanic backarc rift situated in the
continental Australian Plate, is related to subduction of the Pacific Plate along the
Hikurangi margin. The Taranaki Basin contains an almost complete Miocene-Recent
sedimentary record of the evolution of faulting and sub-marine andesitic volcanoes in
the backarc. Detailed study of extensive regional seismic reflection and coastal
outcrop datasets yields valuable information about the extent to which backarc rifting
and reverse faulting have been controlled by the evolution of the Hikurangi margin
subduction. Normal faulting and andesitic volcanism commenced in the northern part
of the basin at ~12 and ~16 Ma, respectively, and were synchronous with contraction
in the southern part of the basin. The rift, contractional faults and folds and volcanism
migrated southwards during the last 12 Ma. Southward migration of faulting was
episodic and geologically instantaneous with 100-150 km increases in the length of
the rift at ~12-8 and ~4 Ma. From ~4 Ma displacement rates in the northern basin
slowed and ceased at ~2 Ma. The death of normal faults in the northern Taranaki
Basin together with sympathetic variations in the timing of faulting and the
overlapping rift geometries between the Taranaki Basin and the Central Volcanic
Region are attributed to displacement transfer between the two rift systems.
Southward migration of andesitic volcanism, rifting and contractional deformation are
consistent with clockwise rotation of the subduction margin associated with slab
rollback coupled with southward motion of the southern termination of subduction
and mantle corner flow.
Tectonics, 29, doi:10.1029/2009TC002634, 2010.