Sediment flux across the Great Barrier Reef Shelf to the Queensland Troughover the last 300 ky

The continental margin off northeast Australia, comprising the Great Barrie r Reef (GBR) platform and Queensland Trough, is the largest tropical mixed siliciclastic/carbonate depositional system in existence. We describe a sui te of 35 piston cores and two Ocean Drilling Program (ODP) sites from a 130 x 240 km rectangular area of the Queensland Trough, the slope and basin se tting east of the central GBR platform. Oxygen isotope records, physical pr operty (magnetic susceptibility and greyscale) logs, analyses of bulk carbo nate content and radiocarbon ages at these locations are used to construct a high resolution stratigraphy. This information is used to quantify mass a ccumulation rates (MARs) for siliciclastic and carbonate sediments accumula ting in the Queensland Trough over the last 31,000 years. For the slope, hi ghest MARs of siliciclastic sediment occur during transgression (1.0 Millio n Tonnes per year; MT yr(-1)), and lowest MARs of siliciclastic (<0.1 MT yr (-1)) and carbonate (0.2 MT yr(-1)) sediment occur during sea level lowstan d. Carbonate MARs are similar to siliciclastic MARs for transgression and h ighstand (1.1-1.4 MT yr(-1)). In contrast, for the basin, MARs of silicicla stic (0-0.1 MT yr(-1)) and carbonate sediment (0.2-0.4 MT yr(-1)) are conti nuously low, and within a factor of two, for lowstand, transgression, and h ighstand. Generic models for carbonate margins predict that maximum and min imum carbonate MARs on the slope will occur during highstand and lowstand, respectively. Conversely, most models for siliciclastic margins suggest max imum and minimum siliciclastic MARs will occur during lowstand and transgre ssion, respectively. Although carbonate MARs in the Queensland Trough are s imilar to those predicted for carbonate depositional systems, siliciclastic MARs are the opposite. Given uniform siliciclastic MARs in the basin throu gh time, we conclude that terrigenous material is stored on the shelf durin g sea level lowstand, and released to the slope during transgression as wav e driven currents transport shelf sediment offshore. (C) 2000 Elsevier Scie nce B.V. All rights reserved.