Structure and stratigraphy of the central Great Barrier Reef

Maintenance and Update Frequency: unknown | Statement: Unknown | The Cainozoic evolution of the central Great Barrier Reef Province has been deduced from shallow, intermediate, and deep focus seismic reflection profiling. For much of its history the province has been dominated by terrigenous sedimentation , principally controlled by the relative height of sea level. The earliest depositional episode recognisable beneath the continental shelf was the infilling of the Queensland Trough rift basin with alluvial fan and trunk stream deposits in the Late Cretaceous to Paleocene. As the region subsided further, this was replaced by a Paleocene to Eocene marginal and shallow marine coastal and marine onlap phase. Three periods of low sea level in the late Oligocene, late Miocene, and late Pliocene to Pleistocene resulted in alluvial sedimentation across the shelf, and fluvial and wave-dominated deltaic progradation at the shelf edge, which produced 10-40 km of shelf out-building. During the intervening periods of high sea level, sedimentation was restricted to coastal deltaic progradation on the inner shelf and onlap of the continental slope by submarine fans, and the upper slope was extensively eroded. The reef facies may have first appeared as a fringing reef in the Eocene, but was only established as an extensive, apparently shelf-dominating facies during high sea levels associated with Pleistocene aggradational phases. The reefs, which appear to be only 150-250 m thick, grew on and occur within siliciclastic fluviatile and deltaic sediments, and not on antecedent carbonate platforms. Reef growth occurred during short periods of high sea level, and during the intervening and longer periods of low sea level the reefs were eroded subaerially. Continual re-colonisation of sites throughout their growth history has produced reefs that are composite features made up of a series of remnant reefs separated by unconformities. A shelf-edge barrier reef system, now generally submerged, occurs along much of the central Great Barrier Reef Province, except near Palm and Magnetic Passages. This has modified upper slope deposition during periods of low sea level by funnelling fluvio-deltaic sediments through gaps in the barrier reef, directly feeding upper slope canyons and depositing submarine fans on the middle and lower slopes. During periods of high sea level the barrier reef has shed fine-grained carbonates and organic material to the upper slope. It appears that the cen