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| Eromanga Sea | |
|---|---|
| Name | Eromanga Sea |
| Type | Inland epicontinental sea |
| Location | Australia |
| Period | Cretaceous |
| Basin countries | Australia |
Eromanga Sea The Eromanga Sea was an epicontinental seaway that inundated much of inland Australia during the Early Cretaceous to Late Cretaceous intervals. It formed part of a system of transgressive oceans related to global Cretaceous seaway rises and interacted with contemporaneous basins such as the Great Artesian Basin, the Basin and Range Province (by analogy), and margins adjacent to the Tasman Sea and Gulf of Carpentaria. Its deposits are integral to regional studies involving the Winton Formation, the Mesozoic stratigraphic framework, and Australian hydrocarbon exploration by companies including BHP and Chevron Corporation.
The sea developed as a result of plate-tectonic and eustatic processes tied to the breakup of Gondwana, with subsidence and accommodation space formed along intracratonic sag basins like the Eromanga Basin and the overlying Great Artesian Basin. Tectonic drivers include the relative motions of the Australian Plate, interactions with the Pacific Plate, and mantle dynamic processes similar to those inferred for the Tasman Fold Belt. Sea-level control links to the Cretaceous greenhouse and global events recorded in the Strontium isotope stratigraphy and sequences correlated to the Cenomanian transgression. Sediment provenance involved hinterland sources such as the Great Dividing Range and reworking by fluvial systems comparable to the Eromanga Basin drainage networks mapped by the Australian Geological Survey Organisation.
At its maximum, the seaway covered large parts of present-day Queensland, South Australia, Northern Territory, and New South Wales, extending across depositional platforms comparable to the Gulf of Carpentaria shelf. Paleogeographic reconstructions employ data from the International Commission on Stratigraphy, paleomagnetic studies like those of the Australian National University, and biogeographic correlations with faunas known from the Winton Formation and the Eromanga Basin. Correlative marine units are recognized alongside the Durham Downs and Toolebuc Formation successions and are integrated with basin models used by the Geological Survey of Queensland and the Bureau of Mineral Resources.
Stratigraphic frameworks encompass formations such as the Toolebuc Formation, the Allaru Formation, and siliciclastic and carbonate units analogous to the Winton Formation and Wallumbilla Formation. Sedimentological signatures include laminated black shales, glauconitic sandstones, and phosphatic horizons, with ichnofabrics comparable to those described in Gault Formation and Niobrara Formation studies. Sequence stratigraphy applies concepts developed by the Society for Sedimentary Geology and correlations to global stages like the Albian and Cenomanian. Diagenetic overprints include calcite cementation and porosity trends relevant to reservoir characterization techniques used by SPE-affiliated researchers.
Marine fossils recorded from the sea include ammonites comparable to taxa referenced in the Treatise on Invertebrate Paleontology, marine reptiles similar to taxa in the Ichthyosauria and Plesiosauria clades, and microfossils such as foraminifera and ostracods used in biostratigraphy by the International Paleontological Association. Terrestrial influx preserved dinosaur remains analogous to those in the Winton Formation alongside plant fossils related to the Gondwanan flora; notable vertebrate discoveries have involved institutions like the Queensland Museum and the Australian Museum. Paleobiogeographic links have been drawn with European and South American Cretaceous assemblages studied by researchers at the Natural History Museum, London and the Smithsonian Institution.
Environmental reconstructions indicate a warm, greenhouse marine setting with variable salinity and episodes of anoxia recorded in organic-rich shales similar to the Kimmeridge Clay and black shale deposits elsewhere. Climate drivers include high atmospheric CO2 concentrations reconstructed using proxies employed by the Paleoceanography and Paleoclimatology community and modeled in studies from the CSIRO and Australian National University. Paleoproductivity and nutrient dynamics are inferred from phosphate nodules and extinction/regeneration events correlated with global perturbations such as the Cretaceous Thermal Maximum.
Sedimentary successions of the seaway host source rocks, reservoirs, and seals that underpin hydrocarbon systems explored by firms including ExxonMobil, Santos Limited, and Origin Energy. Organic-rich intervals akin to the Toolebuc Formation act as petroleum source rocks, while sandstone units within the Eromanga Basin serve as reservoirs evaluated using methodologies from the American Association of Petroleum Geologists and the Society of Exploration Geophysicists. Phosphorite and phosphate deposits have been targets for mineral exploration by entities such as the Queensland Department of Natural Resources and commercial miners.
Research on the seaway has evolved through contributions from early 20th-century geologists associated with the Commonwealth Scientific and Industrial Research Organisation and later stratigraphers at the Geological Survey of Queensland and universities including University of Queensland and Monash University. Nomenclatural conventions for formations and biozones have been standardized following guidelines of the International Commission on Stratigraphy and codified in mapping by the Australian Stratigraphic Units Database. Ongoing work involves multidisciplinary teams from institutions such as the Australian National University, the Queensland Museum, and international collaborators at the University of Cambridge and University of Chicago.
Category:Cretaceous Australia Category:Geology of Australia