--> ABSTRACT: A Sequence Stratigraphic Study of the Tangaroa Sandstone, Taranaki Basin, New Zealand, by Mark J. Gresko, D. W. Jordan, P. R. Thompson; #91003 (1990).

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ABSTRACT: A Sequence Stratigraphic Study of the Tangaroa Sandstone, Taranaki Basin, New Zealand

Mark J. Gresko, D. W. Jordan, P. R. Thompson

Seismic sequence interpretation of the Tangaroa Sandstone, combined with detailed biostratigraphic analysis, well log interpretation, and core descriptions, confirm the Tangaroa as a late Eocene-early Oligocene, sand-rich, submarine fan complex within the Taranaki basin of northwest New Zealand. The Tangaroa Sandstone is underlain by deep-water shales (Eocene Kaiata Formation) and overlain by a thick deep-water limestone (Oligocene Te Kuiti Formation), and typically consists of two, 25-150-m-thick, vertically stacked sandstones, separated by a thin (8 m) limestone.

Seismic isochron thickness maps of the Tangaroa interval display a fan-shaped geometry. Internal seismic facies are dominated by erosional channels are progradational wedges. The erosional channels, to 1-5 km wide and approximately 70-150 m thick, are interpreted us upper to mid-fan

feeder channels. Thin progradational wedges are located basinward of the channels. Paleobathymetic data, based on micropaleontology, indicate a shelf-to-deep-water genesis of the Tangaroa. Conventional core data suggest that the Tangaroa comprises fine- to coarse-grained clastics that were deposited by debris flows, liquified flows, and turbidites.

Using seismic sequence techniques, verified by biostratigraphic control, the Tangaroa Sandstone is subdivided into two sequences: the Lower Tangaroa sequence and the Upper Tangaroa sequence, which formed during two distinct relative lowstands in sea level. The intervening limestone and the overlying Te Kuiti Limestone, apparently were deposited during periods of relative highstands in sea level. The Eocene Oligocene boundary is located in the thin limestone of the Lower Tangaroa sequence.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990