Evolution of faulting and volcanism in the Taranaki Basin, New Zealand, and its implications for Hikurangi subduction.



Giba, M, Nicol, A.1, Walsh, J.J.
1 - GNS Science, Lower Hutt, New Zealand

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.