2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 8
Presentation Time: 9:45 AM


BLAND, Kyle J.1, CARON, Vincent1, NELSON, Campbell S.1, KAMP, Peter J.J.1 and PALLENTIN, Arne2, (1)Department of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand, (2)National Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Greta Point, Private Bag 14-901 Kilbirnie, Wellington, New Zealand, kyle@waikato.ac.nz

Hawke's Bay Basin, on the east coast of New Zealand's North Island, is part of the obliquely-convergent plate boundary through the New Zealand subcontinent. It lies adjacent to where the Pacific plate is being subducted beneath the Australian plate. Hawke's Bay Basin is a forearc basin that has developed since the Late Miocene as a consequence of this interaction and, despite the predominance of a siliciclastic fill of sandstone and mudstone, includes widespread development of shallow-marine limestones of Late Miocene to Early Pleistocene age. These young limestones are cool-water (or temperate) carbonates characterised by common to abundant barnacle debris, and are significant because they accumulated during a time of high siliciclastic sediment input to an actively deforming basin experiencing known eustatic sea-level oscillations.

The limestones can be assigned to examples of “continent-attached” and “continent-detached” carbonate systems, not previously enunciated for temperate settings. These two depositional end members formed along the opposite sides of a tidal current-swept paleoseaway that developed in the Early Pliocene. Limestones of the “continent-attached” realm accumulated along the western margin of the seaway upon a narrow shelf fronting a greywacke hinterland and are typically siliciclastic-rich with common barnacles, ostreids and semi-infaunal bivalves. Carbonates from “continent-detached” settings accumulated towards the eastern side of the seaway on and about thrust fault-controlled paleohighs developed on the inboard margin of an accretionary wedge, are siliciclastic-poor and contain abundant barnacles, pectinids, brachiopods and ostreids.

The paper will compare and contrast the morphodynamic, facies and genetic attributes of the “continent-attached” and “continent-detached” limestones, including their sequence stratigraphic architectures, with the intention of contributing to the rapidly developing knowledge base for shallow-marine cool-water carbonate systems globally.