Multiphase palaeochannel development on the Great Barrier Reef Shelf, Australia

[Extract] Multiple paleochannel systems across the Great Barrier Reef Shelf have long been recognised and several studies conducted that showed channel width and depth and have been assigned to modern fluvial systems. In most cases, simple cross-section have been presented and interpreted to be the result of the sea level lowstand during the last glacial maximum. This despite the fact that channel tracking, for example of the Paleo-Burdekin River Channel, has been proven to be difficult because of several "branches" that apparently developed in the mid and outer shelf area. Here we present a high-resolution analysis of a short section (1 km x 1 km) of the Paleo-Burdekin River system in the mid shelf area that illustrates that both erosional as well as infilling structures are complex and are the result of multi-phase channel development rather than from the last glacial lowstand only. This is in contrast to most published work but in agreement with studies from the Fraser River Paleochannel system. The analysis shows that several erosional features can be depicted based on seismic analysis. The sedimentary structures also demonstrate that the infilling of the channel features was complex. In addition, we show new evidence of the shelf edge Paleo-Burdekin River system that exceeded well our expectations of magnitude of the "delta" system. The size illustrates that during the lowstand, significant erosion and deposition must have occurred along the shelf slope as a result of the River system discarding directly onto the shelf slope.

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Australian Earth Sciences Convention 2008

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0729-011X

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