New Zealand Journal of Geology and Geophysics abstracts

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Late Miocene to early Pliocene biofacies of Wanganui and Taranaki Basins, New Zealand: applications to paleoenvironmental and sequence stratigraphic analysis

Austin J. W. Hendy^*
Peter J. J. Kamp

Department of Earth Sciences
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
email: hendya@email.uc.edu

^*Present address: Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA.

Abstract  The Matemateaonga Formation is late Miocene to early Pliocene (upper Tongaporutuan to lower Opoitian New Zealand Stages) in age. The formation comprises chiefly shellbeds, siliciclastic sandstone, and siltstone units and to a lesser extent non-marine and shallow marine conglomerate and rare paralic facies. The Matemateaonga Formation accumulated chiefly in shelf paleoenvironments during basement onlap and progradation of a late Miocene to early Pliocene continental margin wedge in the Wanganui and Taranaki Basins. The formation is strongly cyclothemic, being characterised by recurrent vertically stacked facies successions, bounded by sequence boundaries. These facies accumulated in a range of shoreface to mid-outer shelf paleoenvironments during conditions of successively oscillating sea level. This sequential repetition of facies and the biofacies they enclose are the result of sixth-order glacio-eustatic cyclicity. Macrofaunal associations have been identified from statistical analysis of macrofossil occurrences collected from multiple sequences. Each association is restricted to particular lithofacies and stratal positions and shows a consistent order and/or position within the sequences. This pattern of temporal paleoecologic change appears to be the result of lateral, facies-related shifting of broad biofacies belts, or habitat-tracking, in response to fluctuations of relative sea level, sediment flux, and other associated paleoenvironmental variables. The associations also show strong similarity in terms of their generic composition to biofacies identified in younger sedimentary strata and the modern marine benthic environment in New Zealand.

Keywords  Wanganui Basin; Taranaki Basin; Miocene; Pliocene; Tongaporutuan; Kapitean; Opoitian; Matemateaonga Formation; biofacies; paleoecology; paleoenvironments; sequence stratigraphy

G03048; Received 19 May 2003; accepted 26 January 2004; Online publication date 1 December 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 769-785
0028-8306/04/4704-0769© The Royal Society of New Zealand 2004

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