QCE Marine Science Practice Questions

About 20 000 years BP, at the end of the last glacial period, sea level was about 120 m lower and the Queensland continental shelf was dry land, so reefs could only grow on the steep outer edge. As ice sheets melted, sea level rose and flooded the shelf, creating large areas of shallow, well-lit water above older (Pleistocene) reef foundations [1]. Corals colonised these drowned foundations and grew upward to keep pace with the rising water [1]. Sea level stabilised about 6500 years BP; reefs then grew up to the low-tide level and spread sideways, forming today's platform, ribbon and fringing reefs and the reef flats on which coral cays later built up [1]. So the modern reef is young (thousands of years) and its position and shape follow the drowned topography of the shelf, even though corals have been in Australian waters for about 500 000 years [1]. Marking: 1 mark each for linking sea-level rise to flooding of the shelf, upward growth on older foundations, stabilisation about 6500 years BP leading to modern reef tops, and the link between reef position and drowned shelf topography.