Abstract

The southern continental margin of Australia is the largest area of cool-water carbonate shelf deposition on the globe. Interpretation of 5495 km of airgun seismic-reflection data in the western part of the Great Australian Bight indicates that the 700-m-thick Cenozoic section of the offshore Eucla basin was deposited largely as a prograding cool-water, middle- to high-latitude carbonate ramp, characterized by widespread development of broad, low-relief, biogenic (bryozoan[?]-sponge), shelf and upper-slope mounds. The succession also contains a spectacular and extensive (>475 km long) buried middle Miocene barrier reef (the Miocene Little Barrier Reef) parallel to the modern shelf edge. This rimmed carbonate platform margin represents an episode of warm-water sedimentation during a global climatic optimum, probably coupled with strong eastward flow of a proto-Leeuwin Current. The late Miocene eustatic sea-level fall produced an areally restricted debris-apron sequence at the foot of the reef escarpment. The carbonate platform is capped by a Neogene cool-water carbonate ramp succession typified by aggradational to sigmoidal sequences, punctuated by periods of cold(?)-water, sea-floor erosion. Interpretation of this succession in the light of global and local tectonic and oceanographic events illustrates the dominant influence of water temperature on carbonate platform and reef growth throughout the Cenozoic.

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