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Book Chapter

A Neogene Carbonate Platform, Slope, and Shelf Edifice Shaped by Sea Level and Ocean Currents, Marion Plateau (Northeast Australia)

By
Alexandra R. Isern
Alexandra R. Isern
National Science Foundation, Arlington, Virginia, U.S.A.
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Flavio S. Anselmetti
Flavio S. Anselmetti
Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
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Peter Blum
Peter Blum
Ocean Drilling Program, College Station, Texas, U.S.A.
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Published:
January 01, 2004

Abstract

More than 1700 km of high-resolution seismic data were collected over the Marion Plateau, northeast Australia, to investigate the influence of sea level and oceanography on subtropical carbonate platforms growing on the plateau surface. Seismic data, interpreted in combination with sediments recovered during Ocean Drilling Program Leg 194 and modern oceanographic data, have enabled characterization of the parameters controlling platform growth and development in this region.

Most modern carbonate platforms, such as the Bahamas Platform, have sedimentation patterns that reflect the prevailing wind direction where sediments are forced off the platform on the leeward side, leaving the windward side relatively sediment-starved. This results in platform asymmetry with steep windward and gentler leeward slopes. The seismic data presented here indicate that the carbonate platforms off northeast Australia, although similar in morphology to the Bahamas Platform in many respects, are dominated by oceanographic currents as the primary energy source creating a similar asymmetrical platform geometry where the upcurrent side of the platform is relatively sediment starved and most sedimentisdepositedonthe downcurrent slope. Currents in the study area are dominated by the southward-flowing East Australian Current that generally flows opposite to the prevailing Southeast Trade Winds. This current likely determines not only the morphology, but also the growth potential of the platforms, as well as the volume and final location of sediment transported from the platform top.

Despite the massive, tablelike structures exhibited in the seismic data, Leg 194 drilling demonstrated that the platforms are almost entirely composed of the remains of cool, subtropical organisms, such as red algae, bryozoans, and larger benthic fo-raminifera. Coralline algae were notably absent from most sequences. These calcite-dominated organic remains have a low diagenetic potential, resulting in uncemented and friable slope successions. Nevertheless, the platform tops are well cemented. The fact that the cool subtropical faunal assemblages produce platform geometries that are similar to tropical carbonates suggests that physical parameters, such as current flow and sea level change, may be more important than biofacies in establishing platform architectures.

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Contents

AAPG Memoir

Seismic Imaging of Carbonate Reservoirs and Systems

Gregor P. Eberli
Gregor P. Eberli
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Jose Luis Masaferro
Jose Luis Masaferro
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J. F. “Rick” Sarg
J. F. “Rick” Sarg
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American Association of Petroleum Geologists
Volume
81
ISBN electronic:
9781629810058
Publication date:
January 01, 2004

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