Overview

Location of Darling Basin in NSW

The Darling Basin is in western New South Wales, covering an area of approximately 100,000 km2 . It comprises 11 troughs (sub-basins), containing mostly Palaeozoic sediments that exceed 8000 m thickness in some troughs. Major stratigraphic units can often be corelated from one sub-basin to another.

The basin extends from Broken Hill in the west to Cobar in the east. In the north, the basin outcrops as far as White Cliffs and Louth, and likely underlies the Eromanga Basin, continuing into Queensland along basement structural lows. Southward, the Darling Basin outcrops at Ivanhoe and Roto, continuing south and southwest under the Murray Basin as the Wentworth, Tararra-Menindee Trough.

With 30 petroleum exploration wells drilled in the basin, most of which were drilled during the 1960s and 1970s, and 1550 km of modern multi-fold seismic coverage, the Darling Basin is relatively underexplored.

Geology

Darling Basin

The Darling Basin contains Late Silurian to Early Carboniferous (but predominantly Devonian) sediments in structurally controlled troughs. The nature of basement is largely unknown, but is underlain in part by Lower Palaeozoic units of the Kanmantoo Orogen and possibly some earlier Proterozoic basement. Outcrop is limited, confined mainly to the eastern and western basin margins or as sporadic occurrences coincident with regional basin structural highs. The majority of the basin is covered by 100 m – 200 m of Cenozoic alluvium, and Murray and Eromanga Basin sediments.

Basin fill is sub-divided into three intervals, based largely on regional seismic data. The oldest is the Late Silurian to Early Devonian Winduck interval. The sediments were deposited in fluvial environments in the west and marine the east. The Mid-Devonian Wana Karnu interval (formerly the Snake Cave interval) unconformably overlies the Winduck interval, and deposition was predominantly in fluvial environments. The Late Devonian Ravendale interval unconformably overlies the Wana Karnu interval. The sediments were deposited primarily in braided stream and alluvial fan environments.

The 11 troughs are the Blantyre, Pondie Range, Poopelloe Lake, Nelyambo, Neckarboo, Bancannia, Cobar, Hillston, Wentworth, Yathong-Ivanhoe and Tararra-Menindee Troughs. Regional magnetic and gravity data, coupled with available seismic data and outcrop geological mapping, shows a good correlation between the troughs and Bouguer gravity lows. Intervening structural highs tend to be less well defined and include the Mt Jack High, Lake Wintlow High, Wilcannia High and the Wonaminta Block (Koonenberry High).

The architecture of the Darling Basin appears to be principally controlled by deformation and erosion. Reinterpretations of data suggest that some troughs shared a common sequence stratigraphic framework and, possibly, common depositional histories. Seismic data, coupled with gravity and magnetic data, suggest strong structural control along virtually all the trough boundaries and regional basement highs. Regional seismic lines imply considerable post-depositional (i.e. Mid-Carboniferous Kanimblan Orogeny) deformation, involving either wrenching or compression. Major basin scale extensional faults are generally not recognised.

Exploration data for the Darling Basin

Exploration data can be obtained through online services. Data for the whole of the Darling Basin is available in the Darling Basin Petroleum Data Pack 2017. It is also available for four troughs, namely the Bancannia Trough Petroleum Data Pack 2018, Pondie Range Petroleum Data Pack 2018, Yathong-Ivanhoe Trough Petroleum Data Pack 2019 and Neckarboo Trough Petroleum Data Pack 2020.

For further information
Coal Resource Assessment and Advice
Phone:
+61 (0)2 4063 6543
coal.geology@geoscience.nsw.gov.au
Postal:
Coal Assessment & Advice, Geological Survey of New South Wales, PO Box 344, Hunter Region Mail Centre NSW 2310
Office:
516 High Street Maitland NSW 2320 Map