GEOLOGY OF THE FLINDERS RANGES and GEOLOGICAL BACKGROUND TO SOUTH AUSTRALIAN SCENERY 

GEOLOGY OF THE FLINDERS RANGES
A very short and basic story.
Dr Victor Gostin, Earth & Environmental Sciences, University of Adelaide
Most of the Ranges consist of an extensive and very thick (15km) sequence of layered sedimentary rocks belonging to, and deposited in the Adelaide Geosyncline, also called the Adelaide Fold Belt or Adelaide Rift Complex, stretching (~600km) from Kangaroo Island north to Mt Painter, South Australia.
This structure was formed some 850 Ma (=million years ago) with the stretching, thinning and sinking of much older crust now seen at Mt Painter, in parts of the Adelaide Hills, and flanked on the west by the Gawler Craton, and on the east by the Curnamona & Broken Hill blocks.
After a very long 350 million years of almost continuous sedimentation, this layered sequence was squeezed and gently folded during the end-Cambrian Delamerian Orogeny (~500 Ma). Deep burial regionally metamorphosed the sediments, and granites were intruded, such as those at Victor Harbor, Reedy Creek, Olary, and Mt Painter. Today's Flinders Ranges are the deeply eroded and exhumed parts of this very thick sedimentary sequence, with soft shales in the valleys and harder sandstones or quartzites forming many of the high ridges.

- - - - - - - - - - -
The whole sedimentary sequence may be divided into five parts, the first two, Callana and Burra Groups, were formed in localised rift valleys involved with the break up of the supercontinent Rhodinia. Basaltic lavas, alluvial fans and saline lakes began the sedimentation. A widening rift sequence of the Burra Group involved extensive marine sandstones, shales and dolomites, with some magnesites as well. These outcrop extensively from Adelaide to Quorn, and northwest of Copley.
A breakup unconformity or erosion surface separates these from the succeeding Umberatana and Wilpena Groups, which together with the Early Cambrian sediments were deposited in shallow seas and along continental shelves.  These include two massive ice ages, involving major sealevel fluctuations and a third cold period (580 Ma) during which a huge asteroid impact created the Acraman structure in the Gawler Ranges, ejecting rock fragments at least 400km distant. This may have contributed to the evolution of the famous soft-bodied Ediacaran fauna preserved in the latest Precambrian, the Ediacaran Period.
Cambrian sediments included shallow marine sands and silts with shelly fossils, and predominant fossiliferous limestones, some as reefs (with sponge-like Archaeocyatha). The youngest Cambrian sequences include basalts, and red deltaic sandstones and siltstones.
.
GEOLOGICAL BACKGROUND TO SOUTH AUSTRALIAN SCENERY
South Australian rocks record numerous episodes of uplift, erosion, deposition, folding, metamorphosis and granitic intrusion that occurred in Cambrian and Precambrian times (before 500 Ma = 500 million years). 
Over 200 million years of erosion from Ordovician to latest Carboniferous (300Ma), removed many kilometres of crust, exposing rocks that had been folded and deeply buried.  These now outcrop in Eyre Peninsula, Flinders Ranges and the Adelaide Hills.
Australia was then part of the Gondwana supercontinent, and it was covered by large ice caps that spread from the south, gouging out and infilling valleys with glacial and meltwater sediments. The widespread vegetated swamps produced Australia’s abundant coal and gas deposits.
Another 180 million years of erosion were followed by very high Cretaceous sea levels flooding vast areas of low-lying Australia. This formed the Great Artesian Basin. Weathering and erosion of the southern edges produced the colourful breakaways of the Painted Desert.
A giant rift opened along Australia’s southern edge where volcanoes erupted, the sea invaded   from the west, and the final breakup of Gondwana began.  Remnants of this low-relief Cretaceous topography are probably the oldest surfaces forming the highest parts of the Gawler, Flinders, and Mt Lofty Ranges.
In the Late Eocene (45Ma) the crust thinned by extension and subsided, forming the Eucla, St. Vincent, and Murray Basins. These were filled with sands, muds and marine shells that formed widespread limestones. The Mount Lofty Ranges rose gently along their eastern side.
A 650 km long coastal dune system of Eocene to Miocene age (10 Ma) is still preserved along the ancient shores of the Eucla Basin. As sea levels fell, coastal erosion resulted in the spectacular limestone cliffs of the Great Australian Bight.
In the Miocene (10-5Ma) the sea retreated from the Murray Basin. The coastal parts were eroded and covered with Pliocene coastal gravels. Oyster beds filled the long estuary of the lower Murray valley.
The last two million years were characterised by multiple sea level fluctuations (up to 140m) linked to climate changing from humid to arid.  The western Mt. Lofty Ranges were elevated due to crustal compression, and rivers like the Torrens and Onkaparinga now cut steep gorges.
The Earth’s crust is continuing to deform as witnessed by beach deposits 120,000 years old that are near sea level at Port Adelaide but have been uplifted to over 10m at Normanville and 16m at Mt Gambier.

We live on an ancient continent, rejuvenated in recent times.