This Sydney Basin dataset contains descriptive attribute information for the areas bounded by the relevant spatial groundwater feature in the associated Hydrogeology Index map. Descriptive topics are grouped into the following themes: Location and administration; Demographics; Physical geography; Surface water; Geology; Hydrogeology; Groundwater; Groundwater management and use; Environment; Land use and industry types; and Scientific stimulus.
The Sydney Basin, part of the Sydney–Gunnedah–Bowen basin system, consists of rocks dating from the Late Carboniferous to Middle Triassic periods. The basin's formation began with extensional rifting during the Late Carboniferous and Early Permian, leading to the creation of north-oriented half-grabens along Australia's eastern coast. A period of thermal relaxation in the mid Permian caused subsidence in the Bowen–Gunnedah–Sydney basin system, followed by thrusting of the New England Orogen from the Late Permian through the Triassic, forming a foreland basin. Deposition in the basin occurred in shallow marine, alluvial, and deltaic environments, resulting in a stratigraphic succession with syn-depositional folds and faults, mostly trending north to north-east.
The Lapstone Monocline and Kurrajong Fault separate the Blue Mountains in the west from the Cumberland Plain in the central part of the basin. The Sydney Basin contains widespread coal deposits classified into geographic coalfield areas, including the Southern, Central, Western, Newcastle, and Hunter coalfields. These coalfields are primarily hosted within late Permian strata consisting of interbedded sandstone, coal, siltstone, and claystone units. The coal-bearing formations are grouped based on sub-basins, namely the Illawarra, Tomago, Newcastle, and Wittingham coal measures, underlain by volcanic and marine sedimentary rocks. Deposition within the basin ceased during the Triassic, and post-depositional igneous intrusions (commonly of Jurassic age) formed sills and laccoliths in various parts of the basin. The maximum burial depths for the basin's strata occurred during the early Cretaceous, reaching around 2,000 to 3,000 metres. Subsequent tectonic activity associated with the Tasman Rift extension in the Late Cretaceous and compressional events associated with the convergence between Australia and Indonesia in the Neogene led to uplift and erosion across the basin.
These processes have allowed modern depositional environments to create small overlying sedimentary basins within major river valleys and estuaries, along the coast and offshore, and in several topographic depressions such as the Penrith, Fairfield and Botany basins in the area of the Cumberland Plain.
