--> Abstract: Controls on the Development of a Modern Nearshore, Terrigenous-Influenced Reef: Low Isles Reef, Great Barrier Reef, Australia, by Tracy D. Frank, John S. Jell, Jon S. Schueth, and Ed Frankel; #90039 (2005)
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Controls on the Development of a Modern Nearshore, Terrigenous-Influenced Reef: Low Isles Reef, Great Barrier Reef, Australia

Tracy D. Frank1, John S. Jell2, Previous HitJonTop S. Schueth1, and Ed Frankel3
1 University of Nebraska-Lincoln, Lincoln, NE
2 University of Queensland, St. Lucia, Australia
3 Vibrosed Analytical, Margate, Australia

Low Isles Reef is one of 46 'low wooded island-reefs' unique to the inner shelf of the Northern Great Barrier Reef, which are thought to represent the final stage in the evolution of platform reefs. This study uses the results of reef flat surveys, petrographic data from surface sediment samples and vibrocores, radiocarbon dates, and historical data dating back to 1928 to quantify rates of change and factors influencing reef development. Results indicate that Low Isles Reef reached sea level ~2700 ybp, in the wake of a highstand ~1 m above present that persisted until ~3000 ybp. These developments were followed by a shift from carbonate sediment production to sediment reworking. Terrigenous input to the reef flat appears to have remained constant through time, with the dominant source being relict (Pleistocene lowstand) sediments of the inner shelf that are frequently put into suspension by waves and tidal currents. Historical changes are related to sediment remobilization during storms, the development of a coral shingle barrier around the windward periphery, and shoreline retreat associated with rising sea level. A 150% expansion in mangrove cover since 1928 has increased the delivery of organic detritus to the reef flat and into a lagoon-like re-entrant on the leeward side of the reef, which serves as the main conduit through which water enters and exits the reef flat during the tidal cycle. Increasingly eutrophic conditions are indicated by a shift from widespread scleractinian coral to a dominance of macroalgae and soft coral.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005