Holocene Erosion of Elizabeth Reef, Tasman Sea, Australia
Elizabeth Reef is one of the southernmost coral reefs in the world. Located at approximately 30° south latitude in the Tasman Sea, this atoll is situated near the southern limit of environmental tolerance of reef organisms. The atoll has a well developed outer reef flat, encrusted with calcareous red algae, and a lagoon consisting of patch reefs, sand flats, and a central mesh-reef complex. A relatively small number of coral species occur, and significant coral growth is restricted to the lagoon. Offshore, there is a well developed erosional spur and grove zone (0 to 8 m; 0 to 26 ft), a deeper buttress zone (9 to 30 m; 29 to 98 ft) and carbonate sand flats (30 to 40 m; 98 to 131 ft) before the steep seaward drop-off. Detailed evaluation of eleven rotary cores from the Elizabeth Reef flat indicates that a period of more active coral growth existed in the past. C age dates on scleractinian corals from the cores indicate a maximum age of about 7000 years BP in the upper 3 to 4 m (10 to 13 ft) of the reef flat, with average accumulation rates of approximately 90 cm per 1000 years. The atoll has reached equilibrium with sea level, and it is now influenced more by erosion than growth.
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Carbonate buildups have long been a focus of intense geological study. An underlying reason is the importance of carbonate buildups as significant hydrocarbon reservoirs. This core workshop is intended to provide a “hands on” look at the subsurface geologic record created by carbonate buildups with emphasis on lithofacies, stratigraphy of buildups and their surrounding deposits, geometry, “reef”-building and sediment-producing organisms, and diagenesis and porosity evolution