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The Murray Basin is an intracratonic basin of Cainozoic freshwater, shallow marine, coastal and continental sediments covering an area of ~330 000 kmē.
Basement to the basin consists of Neoproterozoic to Cambrian metasediments, igneous intrusives and extrusives.
The Tertiary sequence is up to 600 m thick in the west-central Renmark Trough area, but generally 200–300m elsewhere in the basin.
The Cainozoic sediments overlie the Permian Nadda Basin and Cretaceous Berri Basin. The South Australian portion of the Murray Basin is flanked to the west by Adelaidean to Cambrian rocks of the Adelaide Geosyncline and Kanmantoo Trough, and Proterozoic rocks of the Curnamona Province to the north.
Deposition in the Late Paleocene to Early Oligocene was characterised by floodplain and swamp deposits which host significant occurrences of lignite along the western margin of the basin (Renmark Group), and marine sediments (Buccleuch Formation).
Major marine incursions in the Late Oligocene to Middle Miocene resulted in alluvial environments being replaced by lagoonal and marginal marine muddy facies, and deeper water marls and limestones (Murray Group).
A global sea-level fall in the Middle to Late Miocene brought an end to this depositional cycle and led to local erosion and weathering. A rapid marine transgression at the end of the Miocene led to highstand deposition (Bookpurnong Formation), which was followed by progradation of the littoral Loxton and Parilla Sands. The sands are host to concentrations of heavy mineral sand throughout the basin. Quaternary deposits include lacustrine clay and variably dolomitic limestone laid down in the ancient ‘Lake Bungunnia’.
The modern land surface of the Murray Basin consists predominantly of an aeolian dunefield that is cut by the Murray River valley.
