Tidally Incised Valleys on Tropical Carbonate Shelves: An Example from the Northern Great Barrier Reef, Australia

The formation of incised valleys on continental shelves is generally attributed to fluvial erosion under low sea level conditions. However, there are exceptions. A multibeam sonar survey at the northern end of Australia's Great Barrier Reef, adjacent to the southern edge of the Gulf of Papua, mapped a shelf valley system up to 220 m deep that extends for more than 90 km across the continental shelf. Based on observations, we propose a new conceptual model for the formation of tidally incised shelf valleys.