Poster describing how GA made the WASANT palaeovalley map (GEOCAT #73980).

Australia - Evolution of a Continent: Palaeogeographic Atlas

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No product available. Removed from website 25/01/2019

Multibeam sonar mapping, drill cores and underwater video data have confirmed the existence of a previously unknown reef province in the Gulf of Carpentaria, Australia. Seven reefs, comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region. U/Th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10.5 kyr BP, making them the oldest reefs known in Australia. Reef growth persisted for ~2.0 kyr but it had ceased at most locations by ~8.0 kyr BP. Measurements of reef growth rates (0.95 to 4 m kyr-1), indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise (>10 m kyr-1), which is consistent with a 'give up' reef growth history. Core samples from reef platforms demonstrate that Pleistocene limestone is exposed in depths of 27 and 30 m below present mean sea level. These depths represent regionally significant phases of reef growth during a prolonged sea level still stand. We conclude that the reefs are therefore mostly relict features, whose major phase of growth and development relates to an earlier, pre-Holocene sea level stillstand.

No product available. Removed from website 25/01/2019

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Numerous Miocene reefs and build-ups have been identified in the Rowley Shoals region of the central North West Shelf, offshore Western Australia. The reefs form part of an extensive Miocene reef tract over 1600 km long, which extended northward into the Timor Sea and southwards to North West Cape. Growth of the vast majority of these Miocene reefs failed to keep pace with relative sea-level changes in the latest Miocene, whereas reef growth continued on the central North West Shelf to form the three present-day atolls of the Rowley Shoals (Mermaid, Clerke and Imperieuse Reefs). Widespread buildups and atoll reefs developed in the Rowley Shoals region in the Middle Miocene, and their internal stacking geometries indicate successive aggradational, progradational and back-stepping growth phases that are correlated with eustatic sea-level fluctuations. Growth of the majority of the Miocene reefs ceased at a major sea-level fall in the late Late Miocene, and only the reefs of the present-day Rowley Shoals continued to grow after this event. The Rowley Shoals reefs continued to keep pace with Pliocene-Pleistocene sea level changes, whereas the surrounding shelf subsided to depths of 230-440 m. Contrary to previous hypotheses, we find no direct evidence that active, or palaeo, hydrocarbon seepage triggered or controlled growth of the Rowley Shoals reefs or their buried Miocene predecessors. Rather we conclude that initial reef growth was controlled by transpressional reactivation and structuring of the Mermaid Fault Zone during the early stage of collision between the Australia and Asian plates.

Legacy product - no abstract available

Legacy product - no abstract available