LATE QUATERNARY SEDIMENTATION ON THE GREAT-BARRIER-REEF CONTINENTAL-SHELF AND SLOPE EAST OF TOWNSVILLE, AUSTRALIA

Cores collected in a shelf to basin transect from northeastern Australia document the stratigraphic development of late Quaternary deposits. Low sea-level (to - 120 m) slope sedimentation is dominated by prograding fluvial deposits with wave-dominated deltas forming on the shelf edge and upper slope. The onset of sea-level transgression into the excavated shelf river channels on the outer shelf resulted in estuarine sedimentation along an indented coastline (15,000-11,000 yrs B.P.), reducing terrigenous sediment supplies to the slope. On the outer shelf, Halimeda muddy sandy gravels were deposited over a Pleistocene limestone erosional surface from about 10,500 yrs B.P. Transgression submerged the limestone outcrops (and estuaries) of the middle shelf where coral reef complexes formed; the outer and middle parts of the shelf thus became dominated by carbonate sedimentation while the inner shelf received fluvial input mixed with locally derived carbonates. The sequence is bounded by an unconformity, clearly marked by erosional down-cutting. The results of the study are combined with those of previous workers to develop transgressive and continued high sea-level system tract models. The latter (continued high sea level) model is used to extrapolate present high sea-level sedimentation patterns into the future, providing a model for comparison with ancient sequences which may also have formed in such a depositional environment. © 1990.