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| Burrinjuck Group | |
|---|---|
| Name | Burrinjuck Group |
| Type | Stratigraphic group |
| Period | Late Ordovician–Silurian |
| Region | New South Wales |
| Country | Australia |
| Subunits | Burrinjuck Subgroup, Goodradigbee Formation, Adaminaby Formation |
| Namedfor | Burrinjuck Dam |
| Namedby | Sydney Geological Survey |
Burrinjuck Group
The Burrinjuck Group is a stratigraphic succession in southeastern New South Wales near the upper reaches of the Murrumbidgee River and the Goodradigbee River that has been the focus of regional studies by institutions such as the Geological Society of Australia, the Australian Museum, and the CSIRO. It yields comparisons to lithostratigraphic units mapped by the New South Wales Geological Survey and cited in publications from the University of Sydney and the Australian National University. The succession records sedimentary, tectonic, and biotic changes that have been interpreted in relation to events like the Tabberabberan Orogeny and broader episodes preserved across the Great Dividing Range and Snowy Mountains.
The group comprises interbedded siltstone, shale, sandstone, quartzite, and volcaniclastics correlated with formations such as the Adaminaby Formation and the Tumut Group within the Lachlan Fold Belt. Stratigraphic work by teams from the Bureau of Mineral Resources and the New South Wales Department of Mineral Resources has divided the succession into multiple members and facies belts that reflect basin fill documented in the Molong–Stockinbingal Belt and adjacent terranes like the Gilbert River Basin. Structural mapping by field parties associated with the University of Wollongong and the ANU Research School of Earth Sciences highlights folding, thrusting, and cleavage development tied to the Delamerian Orogeny and later reactivation during the Benambran Orogeny.
Fossil assemblages recovered from the succession include diverse trilobites, brachiopods, bivalves, gastropods, and graptolites that permit biostratigraphic correlation with faunas described from the Bermagui Basin, Braidwood District, and classic localities sampled by paleontologists at the Australian Museum and the Queensland Museum. Taxa reported in museum catalogues and monographs published by scholars linked to the University of Tasmania and the Natural History Museum, London enable comparisons with faunas from the Wellington Convincingly Correlative Units and the Antarctic Peninsula sequences. Notable fossil genera reported in the literature include trilobite genera comparable to those in the Balclutha Formation and graptolite assemblages used by researchers at the Smithsonian Institution to refine Silurian biozones.
Sedimentological analyses conducted by researchers from the Australian National University and the University of Sydney indicate deposition in marine shelf to slope settings with episodes of deeper-water anoxic conditions and periodic basin inversion tied to plate interactions involving the Gondwana margin. Volcaniclastic horizons intercalated with the siliciclastic record have been correlated with arc volcanism documented across the New England Orogen and interpreted in work by the Geoscience Australia and the Bureau of Mineral Resources. Radiometric constraints and biostratigraphic zonation link portions of the succession to the Late Ordovician and Silurian, facilitating correlation with units in the Tasmanides and with regional unconformities recognized by the Australian Stratigraphic Commission.
The Burrinjuck Group has been targeted in regional mineral assessments by the New South Wales Department of Mineral Resources and prospecting conducted by companies recorded at the Australian Securities Exchange for its potential base-metal mineralization and as a host to structurally controlled quartz-vein gold occurrences analogous to deposits evaluated by the Geological Society of London and mining geologists from the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Scientifically, the succession provides key paleoenvironmental and tectonic information used by research groups at the University of Melbourne and the Monash University to reconstruct the paleogeography of eastern Australia during Paleozoic orogenic cycles, and it informs conservation work by the National Parks and Wildlife Service (New South Wales) regarding geodiversity in protected catchments.
Prominent exposures occur in the Burrinjuck Reservoir area, valley outcrops along the Murrumbidgee River corridor, and road cuts adjacent to the Hume Highway and secondary roads toward the Snowy Mountains Highway. Geological field guides produced by the New South Wales Geological Survey and field trips organized by the Geological Society of Australia document accessible sections near the towns of Yass, Adaminaby, and Bredbo. Subsurface extents and thickness variations have been imaged in geophysical surveys undertaken by the Geoscience Australia and regional seismic reflection profiles tied into basin models developed at the University of Newcastle.
Naming and early description of the succession were performed by surveyors and geologists affiliated with the New South Wales Geological Survey and later revised through systematic mapping campaigns by the Bureau of Mineral Resources in the mid-20th century. Subsequent stratigraphic refinement and biostratigraphic frameworks were advanced by paleontologists and stratigraphers at institutions including the Australian National University, the University of Sydney, and the Australian Museum, with international collaborations involving researchers from the Natural History Museum, London and the Smithsonian Institution. Ongoing work by academic groups and government agencies continues to reassess boundaries and correlations in light of new geochronology, sedimentology, and paleontological data.
Category:Geology of New South Wales