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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Oral Presentation 2266
Evolution of the Plate Boundary Through New Zealand since 25 Ma Spatialtemporal
patterns of orogenesis
Prof. Kevin P Furlong
Deoartment of Geosciences Penn State University IASPEI
P.J.J. Kamp, G.P. Hayes
The current plate boundary configuration through New Zealand of a (transpressional) continental
transform linking two convergent/subduction zones initiated approximately 25 Ma. Its present
configuration, kinematics, and patterns of deformation serve as a primary example of the tectonic
response to transpressional plate interactions. Although the present situation is reasonably well
constrained, the tectonic history of boundary is less clear. In particular, the extent, geometry, location,
and deformational behavior of the plate boundary linking the Hikurangi and Puysegur subduction
regimes the proto-Alpine Fault (AF) plate boundary structure prior to approximately 10 Ma is not well
understood. Combining plate reconstructions, patterns of basin evolution and volcanism recording the
southward migration of Hikurangi subduction, and plate kinematics through time allow us to place
important constraints on the development of the proto-Alpine fault plate boundary through the Miocene.
Results include (1) a substantial volume of crustal material must have been removed along the proto-AF
adjacent/within the present North Island, implying transpression along that segment of the plate
boundary in the Middle Miocene and the development of a Southern Alps-like orogen bounding the
eastern margin of the present-day North Island; (2) The present North Island subduction margin and
the accretionary margin forearc terranes were likely originally part of the Pacific plate (i.e. east of the
proto-AF) and have been sequentially captured by the Australian plate in a manner similar to present
capture by Australia of the Marlborough terranes in the northern South Island; (3) remnants of the
proto-AF structures should lie inboard of these forearc terranes and may be associated with faults of the
North Island Axial Ranges; and (4) the proto-AF plate boundary may have had different geometry,
orientation, and attitude from the current Alpine Fault through the South Island characteristics that are
in part controlled by the structure and mechanical properties of the Australia plate margin. This analysis
implies that the Alpine Fault system was transpressional throughout much of its history and not only
post-Miocene as is normally assumed.
Keywords: newzealand, alpinefault, ttranspression