Background:

Located in eastern South Australia (east of Lake Torrens), the Flinders Ranges were named for their discoverer, Matthew Flinders, who sighted them as he sailed up Spencer Gulf in 1802. The Flinders Ranges are the most spectacular outcrop of the Adelaide Geosyncline, a rock sequence which dates back 1000 million years. The sequence is up to 33 Km thick and almost 150 Km across - the northern part of this composes the Flinders Ranges. As a brief simplification, the eastern coast of Australia as it is contemporarily known did not exist 1000 million years ago; processes of extension and vulcanism formed this coast and the Flinders Ranges bear evidence of many of these processes.

Human interaction with the ranges since Matthew Flinders’ discovery is a story unto itself.

Many small mines opened, the majority of them exploiting copper deposits; these were highly impractical, as transportation to the smelters cost more than the miners were being paid for the product. The copper formation was a result of the action of diapers and mobile fault lines. In other cases, minerals are leached from the soil and deposited deep in the water table. The mining towns quickly dissipated, although some (such as Blinman, Sliding Rock, Nuccaleena and Yudnamutana) remain today. Others sought different materials and mining still occurs at Leigh Creek (sub-bituminous coal), Oraparinna (barite), Puttapa (zinc) and Mount Fitton (talc). Other deposits are slowly being opened up as more of the Flinders Ranges’ geological structure is mapped. Minerals of which more deposits may be found include uranium, silver, lead, corundum and asbestos.

Early land managers who settled in the area (particularly wheat farmers) were given a false impression of the conditions, soon abandoning their farms when drought inevitably struck. The Flinders Ranges are an archetypical semi-arid mountainous environment, meaning that annual rainfall averages around 250mm and most native vegetation is accustomed to water scarcity; this means it is far too dry for crop growth (the story of agriculture in Australia in microcosm) but conditions are ideal for sheep grazing. Some stations use natural topography in order to pen and trap their sheep. Sheep are the main stock run through the area, although the increase in demand for goat products has led some to consider change. At present, feral goats cause enormous damage to local ecosystems and there are regular attempted purges. The question of whether environmental concerns will prevail is one with great ramifications for the Flinders Ranges’ many endangered species.

A narrow-gauge railway was built from Port Augusta to the Flinders Ranges (via the Pichi Pichi Pass) in 1878. It continued to grow and now reaches as far north as Oodnadatta, connecting regional centres such as Hawker, Copley, Beltana and Marree. When it reached Alice Springs in 1923, it became known as the Ghan. This railway was abandoned for one which ran through the plains west of the ranges - this railway is in service today and conveys coal from the Leigh Creek mine to the power station in Port Augusta, although the old line is now considered a tourist attraction and acquires far more attention. The towns surrounding the Flinders Ranges now rely upon tourism; large sections of the ranges have been incorporated into National Parks and Wildlife Conservation Reserves. Three large National Parks exist (Mt. Remarkable, Warren Gorge and Buckaringa Gorge) although many dilapidated sheep stations now offer historical tours and accommodation in similar fashions.

Water is a valuable resource. Most towns are supplied by small dams or groundwater bores. Unfortunately, groundwater is often too saline for human consumption and some contains magnesium sulphate (Epsom salt). There are, however, sufficient sources to maintain small communities. The largest dam in the area is Aroona Dam, which is sufficient for Leigh Creek and its 2000 inhabitants: built across one of the many steep-sided gorges, the dam is a testament to the erosive power of water as the gorges themselves have been carved out by the infrequent but dramatic periods of rainfall. The impermeability of the basin’s rocks and the steep landforms mean that it is not uncommon for the creeks feeding the dam to rise to a height of several metres after only a few hours of rainfall.

Life in the Flinders Ranges is deceptively diverse. Plant species represented here are generally those with high tolerance for arid environments: the more common of the larger species include eucalypts, callitris pines, mulga and acacias. Shrubs and other small plants include bluebush, wild hops, xanthoreas, grasses (especially Spinifex in the north) and many wild flowers. Kangaroos thrive here and are represented most commonly by the Euro, the Red and Eastern Grey, although rare species like the Yellow-Footed Rock Wallaby are also present (albeit confined to threatened environments in the far north). Birds include parrot species (galahs, sulphur crested cockatoos and rosellas) as well as magpies, crows, murray larks, zebra finches, honeyeaters, emus and wedge-tailed eagles. Reptiles represent the majority of the smaller animals; although there are a myriad of lizards and snakes, their environments are now threatened by feral rabbits (with a brief respite upon the spread of the Colici virus). Insects - as everywhere in Australia - are common.

Introduced species deserve particular mention. Misguided attempts to ‘acclimatise’ Australia to the will of its colonisers failed miserably, although the species themselves thrived. Many paddocks are dominated by Patterson’s curse or Prickly Pear cacti: the former runs rampant, but the latter is subject to control attempts with the release of the South American cacto blastis moth as a preventative measure. Peppercorn trees are present in many towns and homesteads, although they are not found in more remote areas. Rabbits, goats, camels, foxes, cats and dogs are all present and each has contributed to the endangerment of smaller native species, whether through predation or indirectly by competition for water and food sources. The aforementioned purges are also extended to these other species whenever possible. Within the Brachina Gorge area (protected as a National Park), native species are not obliged to compete with introduced species, although the tourist industry has left its own mark.


Geological History of the Flinders Ranges:

There is a trail through Brachina Gorge which enables the traveller to experience the geological significance, ecological diversity and awe-inspiring splendour of the ranges. The following is a recount of significant sites based on notes I took while in the ranges, although it is a travesty that I cannot accompany these with pictures. Apologies for the convoluted terminology.

Stop 1) Enorama Shale:
Description: purplish-weathering grey-green silty and dolomitic shales.
Age: 640 million years.
Comments: the probable depositional environment was a deep marine (anoxic) one as witnessed by the grey-green colour, fine grains and manganese dendrites (the product of manganese precipitating to the ocean floor). The rock is relatively soft and fragments easily; the bedding has a strike of 340° and a dip of 14°.

Stop 2) Trezona Formation:
Description: grey-green calcareous shales, interbeds and lenses of grey or red clay-flake breccia limestones or dolomites with stromatolites.
Age: 630 million years.
Comments: the stromatolites characteristically formed in a shallow, highly saline environment (with few disturbances - the structure is relatively straight), which was periodically inundated: a probable environment is a swamp or lagoon. Such an environment would allow cyanobacteria to accrete with little risk from grazing organisms with low salt tolerance or from environmental hazards. These stromatolites are common until the beginning of the Cambrian Period, when multicellular organisms forced cyanobacteria from their niches.

Stop 3) Elatina Formation and Nuccaleena Dolomite:
Description: well-bedded pink sandstone or massive feldspathic granule greywacke, minor fine-grained purplish sandstone; rare halite casts and ripple-marks (Elatina). Finely-laminated purple dolomitic shales with cream dolomite nodules, basal cream-weathering pink dolomite bands. Local unconformity (Nuccaleena).
Age: 620 million years (Elatina) and 610 million years (Nuccaleena).
Comments: the known depositional environment was an inland sea or lake and the sediments were deposited by an encroaching glacier. The significance of Elatina is in the fact that the glacier is evidence of regional (and possibly widespread global) cooling. By way of explanation, the Australian-Indian tectonic plate would likely have been in a cooler region at the time, later entering a warmer region which created an inland sea. The Nuccaleena Dolomite is significant in conjunction with this because its widespread deposition makes for an excellent geological marker. It was likely formed in warm, shallow seas.

Stop 4) Brachina Formation and Ulupa Siltstone:
Description: olive green and purple siltstone, red-brown, olive green and purple shales, minor sandstone in west (Brachina formation); dark green siltstones in east (Ulupa siltstone); numerous sedimentary structures. Local diapiric detritus.
Age: 600 million years.
Comments: the rippled structure of the Brachina Formation (or ‘slippery dip’ as it is affectionately known) is evidence of formation in a shallow marine environment which saw frequent wave action. The asymmetry of the ripples suggests a single-direction ‘stream flow.’ Further downstream, there is a parasitic fold (anticline) which demonstrates compressional forces. Further downstream still, there is another major tectonic structure - an unconformity. Essentially, the overlaying of the Ulupa Siltstone on the Brachina Formation is a consequence of silt and clay being deposited by a lake (which came into being when a river was dammed by surrounding mountains some 100,000 years later). In itself, this means little but the endurance of the lake suggests a cooler climate and/or higher rainfall rates than at present.

Stop 5) ABC Range Quartzite:
Description: cross-bedded feldspathic sandstone and quartzite, often in two bands.
Age: 590 million years.
Comments: the relative elevation of the peak (by contrast to those in the vicinity which are composed of other materials) displays the fact that quartzite is more difficult to erode than other materials. Many heavy mineral sands are present - the very same type of mineral sands one might find on a beach. This area, therefore, once marked the easternmost coastline of Australia.

Stop 6) Bunyeroo Formation:
Description: red-brown or purple shale, minor red limestones, minor carbonaceous shale, lenticular cream dolomites and phosphatic chert breccias. Local diapiric detritus.
Age: 580 million years.
Comments: The fine-grained structure and type of sediment (clay and silt) suggests deep water deposition. The origin of the rhyolitic material is an interesting story and initially baffled geologists - the Acraman meteorite impacted some 300 Km from the modern Flinders Ranges; the ferocity of the impact was such that pieces of rhyolite were hurled into the air and landed in their current location. Not only this, but the impact would have created a harsh environment in which complex (multicellular) life was better able to survive than its monocellular predecessor. This demonstrates localised extinction and adaptive radiation.

Stop 7) Wonoka Formation:
Description: grey-green shales, grey sandy limestones, minor red-brown and purple calcareous shales, siltstones and dolomite, brecciola limestones in slump zones; stromatolites. Local diapiric detritus. Age: 570 million years.
Comments: again, the likely depositional environment is deep water, although the cross-bedding suggests that the water became progressively shallower - a strike of 360° and a dip of 40°.

Stop 8) Pound Quartzite:
Description: resistant white cross-bedded and ripple-marked feldspathic quartzites and sandstones with Ediacara fauna above red cross-bedded feldspathic sandstones and siltstones, minor orthoquartzites, green quartzites and calcareous sandstone. Local diapiric detritus.
Age: 560 million years.
Comments: the upper member, the Rawnsley Quartzite, is composed of symmetrically ripple-marked feldspathic quartzites whereas the lower member (the Bonney Sandstone) contains red cross-bedded feldspathic sandstones, siltstones and calcareous sandstone. The lower member developed in an estuarine (or similarly shallow, low-energy) environment from clay and silt deposits, whereas the upper was deposited in a beach environment and heated so as to produce a near-pure quartzite sand (hence, the ripple marks).

Stop 9) Scree Slope:
Description and comments: the slope of this hill is heavily eroded - one might think wind or water to blame, but it is in fact simple gravity which produced this sheer slope. As the rocks are heated, they expand - when they cool, they contract. Repetition of this process causes cracking and eventually fragments of rock fall, bringing other pieces with them. This form of gravity-based abrasion is known as colluvism.

Stop 10) Ediacaran Fossils:
Description and comments: fossils of some of the first multicellular life are abundant here. The majority of organisms are soft-bodied and closely resemble modern segmented worms, jellyfish and sea pens; namely, Dickinsonia (don’t laugh), Mawsonites and Charmiodiscus. These life forms are significant because they embody a missing link between monocellular Precambrian and multicellular Cambrian life - where most Cambrian life developed hard body parts, these are still relatively soft. They predate the Cambrian Explosion.

Stop 11) Parachilna Formation:
Description: ripple-marked argillaceous sandstones, shales, lenticular limestone; basal red or purple arcosic sandstone with Diplocraterion. Age: 540-550 million years. Comments: the worm burrows present in the rocks suggest a very shallow marine environment (tidal flats). Eventually, the water level rose and, as a deeper marine environment, permitted the deposition of finer sediments in which the worms could burrow. The sudden abundance of trace fossils is the product of the explosive proliferation of multicellular organisms and the abrupt and distinct difference between rocks means that one can stand on the exact point at which the Vendian period ended and the Cambrian began.

Stop 12) Wilkawillina Formation:
Description: grey, biostromal Archaeocyathid limestones with brachiopods; stromatolitic limestones. Age: 530 million years. Comments: limestone is not eroded as quickly as the material which surrounds it. The presence of Archaeocyathid fossils is interesting: where the Ediacarans are soft and less likely to be completely fossilised, these creatures (with hard body parts) are more durable. Today, corals and sponges dominate the same niches these creatures occupied; corals and sponges are in fact descended from these creatures.

There endeth the tour and my very brief history of the ranges.

Related sites:
1) Eregunda Bore
2) Eregunda Mine
3) Blinman Mine
4) Blinman Cemetery
5) Leigh Creek Coalfield
6) Aroona Dam
7) Puttapa Mine




All of this information was derived from my experience of the Flinders Ranges. As an addendum, I would like to endorse anyone with the means to visit this place. The dry, clipped description I offer here cannot do it justice.

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