The mid-Cenozoic Challenger rift system of western New Zealand and its implications for the age of Alpine Fault inception
The mid-Cenozoic Challenger rift system of western New Zealand and its implications for the age of Alpine Fault inception
Geological Society of America Bulletin (March 1986) 97 (3): 255-281
- Alpine Fault
- Australasia
- Cenozoic
- East Indian Ocean
- Eocene
- faults
- grabens
- Indian Ocean
- lower Miocene
- Mid-Indian Ridge
- Miocene
- Neogene
- New Zealand
- normal faults
- Pacific Ocean
- Paleogene
- plate tectonics
- rift zones
- rifting
- sea-floor spreading
- South Island
- South Pacific
- Southeast Indian Ridge
- Southwest Pacific
- spreading centers
- systems
- tectonophysics
- Tertiary
- West Pacific
- western New Zealand
- Norfolk Basin
- Challenger rift system
Analysis of the structure and sedimentary geology of western New Zealand has identified a middle Eocene to early Miocene continental rift system, 1, 200 km long and 100-200 km wide, named here the "Challenger Rift System". Four phases of rift development occurred: (1) infra-rift subsidence, (2) active axial trough subsidence, (3) expanded rift subsidence involving collapse of the rift shoulders, and (4) incipient sea-floor spreading. The spatial and temporal distribution of these phases identifies a North Island and a South Island rift segment and shows that rifting propagated toward the center of the rift from both ends. The northern segment shows a simple pattern of rifting that is comparable with Vink's model of rift propagation; the southern segment, with locked zones and rift nucleation segments, is comparable to Courtillot's model of rift propagation. The sea-floor-spreading history of the southwest Pacific shows that the northern rift segment probably linked with a sea-floor-spreading center in the Norfolk Basin, and the southern segment linked with the Southeast Indian Ridge. This is corroborated by the good correlation between the ages of sea-floor magnetic anomaly lineations that are aligned with the rift and the biostratigraphic ages of rifting. The probable continuity of the rift system in its early development precludes pre-Miocene transcurrent displacement on the Alpine fault; an early Miocene (23 m.y. B.P.) age of Alpine fault inception is indicated by the age and pattern of rift disruption attributed to compression that originated at the Australia - Pacific plate boundary. The modern Australia and Pacific plates were not discrete entities, therefore, until the early Miocene.