Terrigenous sedimentation in the central Great Barrier Reef lagoon: a model from the Burdekin Region.
Authors / CoAuthors
The central Great Barrier Reef Province is characterised by a mainland prograding terrigenous clastic shoreline and an inner shelf dominated by fluvially derived mud. The Burdekin River acts as a large point source of sediment, which is dispersed to the northwest of the mouth. Fluvial sand is wholly contained within the coastal zone and the sand and gravel components of inner and middle-shelf sediments are largely relict or palimpsest. Vertical accumulation of terrigenous mud is limited to a thin veneer on the inner shelf and is negligible on the middle shelf. Coastal progradation accounts for the bulk of Holocene terrigenous sedimentation, which decreases in a northwesterly direction, from 2.5 m yr-1 at the present delta front to 0.1 m yr-1 on the coastal plain north of Townsville. Progradation of the shoreline occurs as four distinct sedimentary assemblages (beach-ridge plain, chenier plain, mangrove-mud-flat plain, and barrier bar-lagoon complex). The overall prograding coastal wedge, where preserved in the geological record, would have recognisable seismic stratigraphic elements (coastal onlap and toplap, distal down lap and marine offlap). The pattern of late Quaternary sea-level oscillations suggests that terrigenous marine and/or alluvial sediments should predominate across most of the shelf of the Great Barrier Reef lagoon.