This resource contains a predicted seabed gravel content grid for the greater Darwin Harbour region as part of a baseline seabed mapping program of Darwin Harbour and Bynoe Harbour. This project was funded through offset funds provided by an INPEX-led Ichthys LNG Project to the Northern Territory Government's Department of Environment and Natural Resources (NTG-DENR) with co-investment from Geoscience Australia (GA) and the Australian Institute of Marine Science (AIMS). The intent of this program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps and information to underpin marine resource management decisions. The predicted seabed gravel content grid was derived from a compilation of multiple surveys undertaken by GA, AIMS and NTG-DENR between 2011 and 2017, including GA0333 (Siwabessy et al., 2015), GA0341 (Siwabessy et al., 2015), GA0351/SOL6187 (Siwabessy et al., 2016), GA4452/SOL6432 (Siwabessy et al., 2017), GA0356 (Radke et al., 2017), and GA0358 and GA0359 (Radke et al., 2018), adding to those from a previous survey GA0333 collected by GA, AIMS and NTG-DENR. This dataset provides spatially continuous predictions of seabed %gravel (>2000 µm) content for the Darwin and Bynoe harbour region, northern Australian marine margin. Data are presented in 10 m resolution raster grids format and ascii text file. Predictions are based on 395 samples and 14 environmental variables derived from high resolution multibeam sonar bathymetry and backscatter data. Accuracy of predictions is high, with a VEcv = 59% for gravel; and the predictive accuracy has been increased by 68.4% for gravel in comparison with the commonly used method (i.e., IDW). Absences in predictions occur in this dataset as a result of non-availability associated with predictive variables. This dataset supersedes previous predictions of mud content for the Darwin and Bynoe harbour region with demonstrated improvements in predictive accuracy.

<div>Geoscience Australia maintains a national collection of marine geological samples and analytical data from across the Australian region. Digital records of these datasets are held within the Marine Sediment Database (MARS), available as an online resource of c. 2.6 million entries. Here we have extracted data from MARS to collate sediment properties for over 15,000 seabed samples for use as a standalone dataset. Analytical data includes textural composition (mud, sand, gravel), summary statistics for particle size distributions, textural class and calcium carbonate values (where available). Information on sample water depth, location and marine survey is also provided. The sample set spans the coast, continental shelf, slope and deep ocean locations across the Australian marine region (covering the extent of the AusBathyTopo 250m 2023 grid). This dataset has utility for a broad range of purposes including seabed characterisation, sediment transport modelling, habitat characterisation, seabed engineering studies and fundamental geological and sedimentological research.</div><div><br></div><div>Additional metadata of this dataset are provided in the word document accompanied with the dataset. The metadata document describes the attribute table, the sediment carbonate classification and the sediment facies.</div>