The geological situation we see in South Australia today is merely a 'snapshot' within a continuous and dynamic development of our Earth.
Through the enormous span of geological time, there have been several cycles of assembly of land masses (continents) into supercontinents that subsequently have broken up into different fragments and become dispersed by the action of continental drift. This process has continued until the present day, and will continue into the future.
As a consequence of our position within the Australian continent, every Period is represented in South Australia’s rock record, and the state’s mineral and petroleum resources encompass a wide range of commodities and associations. Geologists classify the rocks of a region by correlating, or grouping them together, on the basis of similar age, interpreted origin, and lithology, and frequently apply stratigraphic names (e.g. Sleaford Complex) to these groupings as an aid to communication. The following description of the State’s geology is arranged in order from the oldest events and rocks to our present day environment. Refer to the geological time scale as you follow our state’s geological history through time.
The Clare Valley is not so much a valley as a series of mostly north–south ridges and valleys in the undulating hills of South Australia’s Mid-North. Most of the vineyards are situated between the two highest ridges, that to the west being formed of Rhynie Sandstone and that to the east of Gilbert Range Quartzite, though more recent plantings have extended eastward from there onto the more subdued hills underlain by siltstone of the Tapley Hill Formation. What is the origin of these and other ancient rocks from which the rich soils of the Clare Valley, so favourable for growing vines, are derived? What do they tell us about the history of the region?
Walk through geological history with rocks ranging from 600 million years ago to present day - Hallett Cove is one of the best known geological sites in Australia, because of the evidence of an ancient glaciation discovered in 1875 by Professor Ralph Tate from the University of Adelaide. The polished and striated glacial pavements, and sediments associated with the glaciation, are now known throughout the world. The area has been declared a geological heritage site by the Geological Society of Australia and placed on both the South Australian Heritage Register and the former Register of the National Estate because of its significance for educational and scientific purposes.
Conservation of the site to protect the glacial pavements commenced in 1960 with acquisition of a strip of coastline, named the Sandison Reserve, by the National Trust. When subdivision for housing threatened the site, the state and federal governments acquired and purchased adjoining land which was dedicated as the Hallett Cove Conservation Park in 1976.
View the Hallett Cove Discovery Trail (including drone footage)
Volcanic activity occurred in the Mount Gambier area in recent geological time. The outbursts, which would have been spectacular, took place along the edge of the main zone of activity centred on southern and western Victoria, and south-eastern South Australia.
In most cases, the eruptions were along lines of crustal fissuring, starting with small flows of black basalt lava. The shallow regional water table led to interactions with the hot rock and eventually to the rapid accumulation of steam. Activity changed as the lava flows were followed by explosion craters and blowholes, from which thick deposits of ash and scoria were ejected. Mount Schank and Mount Gambier represent the final phase of this activity and are the youngest volcanoes in Australia.
The Earth’s crust can be likened to a ball with a soft centre and an outside shell cracked into many segments. These segments are continuously moving as they float on this soft centre. Sometimes the edges of the segments rub against each other releasing a large amount of energy — this is felt as an earthquake. The science of measuring and recording the movements is called seismology. The location of an earthquake can be determined by using a network of recording stations and method similar to triangulation where information from 3 different recording instruments, seismometers, is used.
There are 44 stations (in 2013) located throughout South Australia, mainly around the Adelaide and mid-north regions. Earthquakes occur far more often in South Australia than most people realise. It is common for there to be 10–20 earthquakes per month with magnitudes between 1 and 2. These mostly go unreported because they are too small to be felt, however the sensitive instruments can detect them. On average, there is one magnitude 4 earthquake each year, with a magnitude 6 earthquake about every 50 years.
Groundwater is difficult to find in Australia’s outback, and is a most precious resource. Recent collaborations with DEW and the Goyder Institute have allowed DEM geologists to assist with providing reliable groundwater resources for outback communities. Geologists use remote sensing, geophysical surveys and mapping to look for ancient river beds that may provide fresher water deep below the ground.
Over 75% of the state is covered by transported regolith material. Regolith is continuously formed and modified, and what we observe in today’s landscape is a result of past, present and ongoing events.
The Department of Energy and Mining has a series of landsat images showing the location of:
major operating and approved mines and producing basins
mines under care and maintenance
developing mineral, petroleum and geothermal projects
successful gas and oil wells
ports and proposed ports.
Of particular interest are:
South Australian copper occurrences showing occurrence type and economic significance and mineralisation type
The South Australian commodity resource, exploration and production dashboard (access via SARIG)
Copper map layers, available via SARIG (click All Map Layers and search copper)
A digital platform providing global access to South Australia's key geoscience information, mining and exploration project information.
The SARIG online bookshop has free downloads available, and the option to purchase hardcopy publications.
Geological maps and map data are available as free digital downloads via SARIG either as preset pdf map sheets or GIS spatial layers, or as plot-on-demand maps. Published hard copy maps are available for purchase via the SARIG online shop.