The northeast Australian margin is the largest extant tropical mixed siliciclastic-carbonate depositional system. For more than 500 k.y. (Davies and McKenzie, 1993; International Consortium for Great Barrier Reef Drilling, 2001), rivers have discharged large masses of clay, quartz, and other weathered residue from the Australian continent into a region with an extensive network of carbonate reefs on the outer shelf, the Great Barrier Reef (GBR). The Marion Plateau (Fig. F1) lies east of the main GBR system, acting as a repository for carbonate material shed from the GBR platform as well as siliciclastic sediments sourced from the Australian landmass (Shipboard Scientific Party, 2002a). The plateau also accumulates carbonate sediments sourced from pelagic rain and local reef systems detached from the high-density reef network on the adjoining GBR shelf.
Fluctuations in eustatic sea level are widely believed to be the primary control on off-shelf fluxes of siliciclastic and carbonate sediments along passive continental margins (e.g., Vail et al., 1977; Walker, 1992). The northeast Australian margin is no exception, although considerable conjecture surrounds the specific processes affecting sediment transport and the timing of off-shelf sediment fluxes in relation to specific phases of eustatic sea level (e.g., Harris et al., 1990; Peerdeman and Davies, 1993; Dunbar et al., 2000; Kronen and Glenn, 2000; Page et al., 2003). Ocean Drilling Program Hole 1198A (Fig. F1) provides a relatively expanded record of mixed siliciclastic-carbonate deposition on the Marion Plateau from the late Pliocene to Pleistocene (Shipboard Scientific Party, 2002b). The site contrasts with the more heavily investigated Queensland and Townsville troughs north of the plateau because a significantly wider shelf separates it from fluvial sources of siliciclastic sediment.
This data report does not attempt to quantify the rates of sediment accumulation at Hole 1198A or resolve the question of off-shelf sediment fluxes and their relation to variations in eustatic sea level (cf. Page et al., 2003). The high-resolution record of variations in bulk carbonate content, however, should prove useful for future studies that may address these questions, as well as other problems relating to the evolution of the mixed siliciclastic-carbonate margin of northeastern Australia.