New Zealand Journal of Geology and Geophysics abstracts

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Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke’s Bay, New Zealand

Vincent Caron
Campbell S. Nelson
Peter J. J. Kamp

Department of Earth Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
email: c.nelson@waikato.ac.nz

Abstract  Pliocene limestone formations in central Hawke’s Bay (eastern North Island, New Zealand) accumulated on and near the margins of a narrow forearc basin seaway within the convergent Australia/Pacific plate boundary zone. The active tectonic setting and varied paleogeographic features of the limestone units investigated, in association with probable glacioeustatic sea-level fluctuations, resulted in complex stratigraphic architectures and contrasting types of carbonate accumulation on either side of the seaway. Here, we recognise recurring patterns of sedimentary facies, and sequences and systems tracts bounded by key physical surfaces within the limestone sheets. The facies types range from Bioclastic (B) to Siliciclastic (S) end-members via Mixed (M) carbonate-siliciclastic deposits. Skeletal components are typical cool-water associations dominated by epifaunal calcitic bivalves, bryozoans, and especially barnacles. Siliciclastic contents vary from one formation to another, and highlight siliciclastic-rich limestone units in the western ranges versus siliciclastic-poor limestone units in the eastern coastal hills. Heterogeneities in facies types, stratal patterns, and also in diagenetic pathways between eastern and western limestone units are considered to originate in the coeval occurrence in different parts of the forearc basin of two main morphodynamic carbonate systems over time.

Keywords  cool-water limestones; carbonate platforms; attached platforms; detached platforms; depositional facies; stratigraphic architecture; Pliocene; Hawke’s Bay

G03040; Received 16 April 2003; accepted 16 September 2003; Online publication date 1 December 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 697-717
0028-8306/04/4704-0697 © The Royal Society of New Zealand 2004

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