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| Lamington Volcanics | |
|---|---|
| Name | Lamington Volcanics |
| Period | Late Oligocene–Miocene |
| Type | Volcanic province |
| Region | Queensland, New South Wales, Australia |
| Unitof | Tweed Volcano province |
| Thickness | variable |
| Lithology | basalt, rhyolite, dacite, tuff |
Lamington Volcanics The Lamington Volcanics are an extensively exposed volcanic suite in eastern Australia associated with the remnants of the Tweed Volcano complex. They record a protracted volcanic history that influenced regional topography, hydrography and biogeography across what are now parts of Queensland and New South Wales, and they have been the subject of field studies by institutions such as the University of Queensland and the Geological Survey of New South Wales.
The Lamington Volcanics lie within the broader geology of the New England Orogen, the Great Dividing Range and the Tweed Volcano region and are structurally related to features mapped by the Australian Geological Survey. Tectonic interpretation invokes interactions between the Australian Plate, the Indo-Australian Plate boundary and ancient intraplate stress regimes that also produced volcanic provinces like the Warrumbungle Volcanics and the Newer Volcanics Province. Regional mapping connects Lamington units to physiographic elements such as the Scenic Rim, the Border Ranges and caldera remnants near Mount Warning, and research by geologists from CSIRO and the University of Sydney has emphasized links to rift-related magmatism, hotspot influences similar to those inferred for the Lord Howe Rise, and crustal controls recognized in studies involving Geoscience Australia and the Australian National University.
Stratigraphic frameworks for the Lamington succession were developed following lithostratigraphic work by state surveys and academic groups including the Australian Academy of Science and involve correlation with Oligocene–Miocene sequences elsewhere in eastern Australia. Radiometric ages obtained by laboratories at ANSTO, Australian National University and international collaborations using K–Ar and 40Ar/39Ar techniques place many flows and pyroclastic units within a Late Oligocene to Miocene interval contemporaneous with eruptive phases documented for the Tweed Volcano and correlated with sequences in the Clarence Moreton Basin and Gloucester Basin. Stratigraphic subdivisions reference unconformities recognized by field teams from the University of New England and sequence stratigraphy comparable to that applied to basins by the Bureau of Mineral Resources.
The Lamington suite comprises diverse lithologies including tholeiitic and calc-alkaline basalts, andesites, dacites, rhyolites, welded tuffs and volcaniclastic breccias that have been petrographically examined by specialists at institutions such as the Australian Museum and Macquarie University. Mineral assemblages commonly include plagioclase, pyroxene, amphibole and biotite with accessory ilmenite and zircon; geochemical fingerprints investigated using ICP-MS and XRF at research facilities like CSIRO and ANSTO indicate trace-element patterns that have been compared to those of the Lachlan Fold Belt and the Newer Volcanics Province. Petrologic models draw on thermobarometric studies from research groups at the University of Melbourne and the University of Tasmania to infer magma evolution via fractional crystallization, crustal assimilation and magma mixing analogous to processes postulated for Mount Warning and the Glass House Mountains.
Surface expressions of the Lamington Volcanics include flow tongues, shield-like constructs, domes, scoria cones and extensive pyroclastic aprons that have influenced local drainage and formed escarpments and plateaus studied by the National Parks and Wildlife Service and local shire councils. Remnant caldera-related topography near Mount Warning, cliffed basalt platforms akin to those seen at Carnarvon Gorge, and columnar-jointed flow exposures attract geomorphological research from the University of Newcastle and field campaigns by the Royal Society and Geological Society of Australia. Structural mapping of faults and dykes performed by field teams from the Australian Geological Survey identifies relationships to regional fault systems such as those documented by the Sydney Basin and Clarence structural studies.
Depositional models for the Lamington succession integrate subaerial effusive eruptions, explosive pyroclastic deposition, lahar deposition and fluvial reworking consistent with volcanic arc and intraplate settings interpreted in comparative studies by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI). Sedimentological work by research groups at the University of Wollongong and James Cook University documents interbedded volcaniclastic sandstones, lacustrine tuffs and soil paleosols that reflect episodic volcanic pulses and climatic modulation similar to records from the Darling Downs and the Illawarra Coal Measures. Numerical modelling and geophysical surveys conducted with collaborators at Geoscience Australia and the Australian National University have been used to reconstruct emplacement mechanisms and paleotopography.
Although primarily igneous, parts of the Lamington succession host intercalated sedimentary lenses preserving plant macrofossils, pollen and occasional vertebrate remains studied by palaeobotanists at the Queensland Museum and the Australian Museum. Palynological assemblages correlate with Australian Oligo–Miocene floras described in work by the Australian National University and international comparisons through the Paleobiology Database help constrain paleoclimatic interpretations that tie to Cenozoic transitions documented in studies involving the CSIRO and the Bureau of Meteorology. Fossil-bearing horizons inform reconstructions of rainforest refugia and biogeographic patterns investigated by researchers from the University of New South Wales and the Australian National Herbarium.
The Lamington Volcanics influence groundwater systems, soil fertility and land use patterns assessed by state water authorities and agricultural research bodies such as the Department of Agriculture and Fisheries and the NSW Department of Primary Industries. Basalt-derived soils support intensive horticulture in parts of the Scenic Rim and are of interest to agronomists from the University of Queensland and the Department of Agriculture. Conservation and tourism values are managed by the National Parks and Wildlife Service and local councils; geotourism initiatives and educational outreach have involved partnerships with museums, universities and organizations such as the Australian Geoscience Council and the Geological Society of Australia.
Category:Geology of Queensland Category:Volcanism of New South Wales