Late Cretaceous coeval multi-directional extension in South Zealandia: Implications for eastern Gondwana breakup

Abstract

Abstract Gondwana continental crust in South Zealandia was deformed by Cretaceous rift faults with multiple orientations. Our interpretation of 2D and 3D seismic reflection lines, tied to wells in the Canterbury Basin of South Zealandia, shows three coeval sets of faults with trends of NE-SW, E-W and NW-SE. Geometric and displacement analyses of segmented faults from each set suggests that they mainly accommodated normal dip-slip, producing multi-directional stretching . Growth strata indicate that the three fault sets were active synchronously over ~20 Myr from ~105 to ~85 Ma. The fault sets are present throughout Zealandia and roughly parallel to spreading centres produced during Gondwana breakup, primarily defining the present-day margins of Zealandia. Faults trending NE-SW and E-W are parallel to the mid-ocean ridge separating South Zealandia and western Antarctica, ~800–1000 km from the Canterbury Basin, while NW-SE rift faults are sub-parallel to the spreading centre between Australia and North Zealandia. Sub-parallelism between spreading centres and rift faulting is consistent with a model in which the multiple directions of extension produced mild ( 500 km) from these centres ceased or continued at much diminished rates.