|List||National Heritage List|
|Legal Status||Listed place (11/01/2007)|
|Place File No||3/00/260/0232|
|Summary Statement of Significance|
The Ediacara Fossil Site - Nilpena is one of the most intact and rich Ediacara fossil sites in the world, and also the least
disturbed Ediacara site in Australia. It provides a unique
opportunity to study a magnificent array of fossils of the internationally
significant Ediacara biota as they were deposited
over 540 million years ago. The site provides the earliest known evidence of
multicellular animal life on Earth.
The Ediacara Fossil Site - Nilpena has produced some of the most spectacular Ediacara fossils ever discovered, including the single largest Ediacara fossil ever found, a specimen of the flatworm-like Dickinsonia rex, nearly 1m long. More fossils have been found at the site than the entire holdings of fossils at the South Australian Museum gathered over years of collecting in the wider Flinders Ranges region. The site has also produced what is thought to be the earliest known ancestor to vertebrates (animals with a backbone) and a range of entirely new species of unknown biological affinities and unknown from other Ediacara sites.
The fossils present a diverse and exquisitely preserved assemblage, representing a significant time period our geological heritage. To date, over 150 square metres of fossil-bearing sea floor have been excavated and retained on-site, providing an unparalleled glimpse of an ancient sea floor and enabling detailed environmental and population studies of the Ediacara biota.
Fossil Site - Nilpena is located on the western
margins of the Flinders Ranges in South
Australia. This recently discovered site represents
some of the best fossil evidence for the oldest multicellular
animal life on the planet. The site has yielded a diverse range of specimens,
including spectacular impressions of the largest known early animals, Dickinsonia rex, and fossils of what may be the
earliest known ancestor of animals with a backbone (vertebrates). |
In 1946 whilst undertaking mineral exploration, geologist Reginald Sprigg discovered fossil imprints in rocks located in low hills of the western Flinders Ranges at the old Ediacara mine field. The fossils he found were the first abundant evidence of multicellular animal life that predated the Cambrian (545 million years ago). In his published descriptions of the fossils, Sprigg (1947, 1949) regarded the fossils as being of early Cambrian age, however subsequent extensive mapping and stratigraphic work confirmed the Precambrian dating of the Ediacara fossil assemblage (Glaessner, 1984; Preiss, 2005). Sprigg named the group of fossils after the area in which they were found; the Ediacara Hills. The name ‘Ediacara’ or ‘Idiyakra’ is derived from an Indigenous term linking it to a place near water (Knoll et al., 2004). Alternatively, recent linguistic research suggests that ‘Ediacara’ as a mispronunciation of the two words ‘Yata Takarra’ meaning hard or stony ground in reference to the flat Ediacara plateau of dolostone that forms the centre of the Ediacara syncline (McEntee, pers comm.).
Since their initial discovery, other localities of Ediacara fossils have been discovered in the Flinders Ranges region, as well as in the Alice Springs region and in the Officer Basin in South Australia. At least 30 other Ediacara localities are now known globally including sites in Namibia, Russia, Newfoundland, Canada, UK and Siberia. Russia and Australia are the two regions that show the greatest diversity of fossil species (Gehling et al., 2005). While the fauna has a wide distribution globally there are significant differences in the make-up of assemblages at different localities. For example, the Australian and Russian forms are similar and the rocks are indicative of a shallow water ecosystem while the assemblages in Canada are indicative of a deep water environment (Johnson, 2004).
Ediacara fossils date from around 570 to 540 million years ago. They first appear in the fossil record above the last Neoproterozoic glacial deposits and disappear near the level of the first shelly-style Cambrian fossils. During this time the region of the Ediacara Fossil Site - Nilpena was a shallow sea at the edge of an ancient landmass comprising what would become western South Australia and Western Australia. East of the site lay open ocean, as the eastern states formed several hundred million years later. The site is thought to represent organisms which were stranded in tidal flats bordering lagoons along the ancient coastline (McBriar & Giles, 1984).
The Ediacara Fossil Site - Nilpena contains fossils of soft-bodied organisms from the early Precambrian and the impressions record the first known radiation of multicellular animal life on Earth. The evolution of the first metazoans, the Ediacarans, is one of the primary events of the Precambrian, and fossil sites preserving Ediacara fossils have been identified internationally as sites of potential world heritage value, with the Flinders Ranges region noted as a preferred site (Wells, 1996). The discovery of an entire community of Precambrian organisms has led to a complete reappraisal of how multicellular organisms are preserved in the fossil record, thereby contributing to the body of knowledge regarding the evolution of life.
The rapid increase in abundance, size, complexity and diversity of life forms during this time shows that the earth underwent a period of major evolutionary change (Grey et al., 2005). The Ediacara sea floor assemblages have one distinct advantage over most younger fossil assemblages, in that their bedding surfaces provide a fossilised snapshot of entire communities at the time of their burial (Gehling et al, 2005; Clapham & Narbonne, 2002; Clapman et al, 2003; Droser et al., 2004).
The soft bodies were preserved in unusual conditions allowing for their impressions to be preserved as casts and moulds of the original organisms. In some cases an external mould of the upper surface of the fossil is preserved on the base of the sandstone as an impression, in other cases the organism collapsed or decayed so that sand filled the space previously occupied by the organism producing a cast, visible as a positive relief on the base of the sandstone (Selden & Nudds, 2004). The fossils are restricted to a narrow band of rock known as the Ediacara Member of the Rawnsley Quartzite, a 500m thick formation that outcrops at a number of points around the Flinders Ranges. Research on-site has shown that more than one type of fossil bed occurs within the Ediacara Member and that these beds may contain a range of depositional environments ranging from inter-tidal zones to shallow protected marine areas.
Unlike other Ediacara sites, including the Ediacara Conservation Reserve (Sprigg’s original discovery site where the significance of the fauna was first fully recognised), the Ediacara Fossil Site - Nilpena has not been subject to fifty years of intensive specimen collecting. In contrast to other Ediacaran localities, a decision has been made by palaeontologists researching the site, the South Australian Museum and the University of California, not to remove excavated material for research purposes. Instead, over 150 square metres of seafloor has been excavated, inverted and laid out on-site for scientific study, providing an internationally unique opportunity to view and study the reconstruction of an ancient seafloor much as it appeared over 540 million years ago.
The exposed slabs at the site contain more fossils than the entire holdings of Ediacaran material held in the South Australian Museum after fifty years of collection from other sites. The fossils present a variety of specimens including anemones, annelid worms, crustaceans, echinoderms and possible ancestors of trilobites. Many entirely new species have been discovered, some bearing no resemblance to any other known organism from the fossil record. Debate continues within the palaeontological literature as to how these fossils should be classified. For example, many rounded forms that were once thought to be jellyfish-like creatures, are now interpreted as the imprints of the anchors of another Ediacara fossil, Charniodiscus, which itself has been interpreted as either related to, or occupying a similar niche to, modern sea-pens. In addition, there are suggestions that some organisms represent early algae, lichens or even multicellular 'experiments' which bear little resemblance to any extant organisms on Earth today.
The majority of Ediacara fossils are rounded forms and were originally classified as jellyfish. As mentioned above, other forms resemble modern sea-pens and worms. Spriggina, possibly an arthropod, looks like a cross between a bristleworm and a trilobite. Tribrachidium heraldicum is a disc-shaped form with a three-part symmetry, whose biological affinities remain a mystery, with distant relations proposed with either cnidaria or echinoderms. Dickinsonia is perhaps the archetypal creature of the Ediacara fossils and consists of a flat impression, circular to ribbon-shaped with fine segmentation. Five species have been described from South Australia (Gehling et al., 2005; Sprigg, 1947; Sprigg, 1949; Glaessner & Wade, 1966; Wade, 1972). Dickinsonia has been interpreted over the years as a cnidarian (jellyfish), a polychaete (worm), a member of a new kingdom of organisms (the Vendobionta), a lichen or possibly a stem group chordate. Current consensus is that it belongs to a new group within the animal kingdom with no near modern relatives. Well preserved specimens of large organisms such as Dickinsonia up to 1m in length and probably less than 1cm in width are preserved together with smaller taxa as well as trace fossils. Associations of taxa such as Dickinsonia, Parvancornia, Spriggina, Tribrachidium and Rugoconites, coupled with the lack of evidence for the transport of the organisms, indicate a community of benthic organisms preserved in life position (Gehling et al., 2005). The site has also yielded what is thought to be the world’s oldest known fossil chordate, now held at the South Australian Museum, which is a 6cm long body mould of the first known animal from the phylum to which vertebrates belong (SAM, 2003).
Preserving the excavated fossils on-site is providing enormous benefits to the scientific community by allowing a much closer scrutiny of the fossil evidence of Ediacara communities in-situ. Although there is still little agreement about the biological affinities of the Ediacara biota, new trace fossil evidence is helping to improve the understanding of their environmental settings and taphonomy (the processes responsible for organisms becoming part of the fossil record, Gastaldo et al., 1996). Researchers are undertaking ecological studies at this site using trace fossil evidence to provide a greater contextual understanding of the inter-relationships between species.
The significance of the Ediacara fossil assemblage recently gained the ultimate geological recognition with a decision by the International Union of Geological Sciences to ratify a new formal geological period for inclusion into the geological time scale, the “Ediacaran Period”. The Ediacaran Period covers an interval of around 88 million years from 630-542 million years ago and is the first new period of geological time to be adopted for over 100 years (Grey et al., 2005) and the only one to be named after a locality in the Southern Hemisphere (Preiss, 2005). The start of the new Ediacaran Period corresponds to the end of a world wide glaciation known as ‘Snowball Earth’ and a distinctive change in carbon levels; the end of the Ediacaran Period is followed by the evolutionary explosion of animal life in the Cambrian Period (Ogg, 2004; Rohde, 2005). The Cambrian is the period where we see a rapid increase in marine animal species in the fossil record and the first hard evidence of predation and burrowing activities, together with species evolving to occupy various niches and complex ecosystem processes.
|Condition and Integrity|
A tennis-court sized area has been surveyed and used for
excavation of several fossil-bearing sections of seafloor. Excavated fossil
material is not being removed from the site, but inverted and reconstructed for
scientific study on-site. Previous palaeontological
work (1998-2000) has resulted in the removal of several slabs and has caused
some site disturbance, however, the current practice
is to replace slabs as found during exploration. The leaseholder is actively
engaged in discouraging the removal of material. A small number of access
tracks are present, mainly following creeklines.
Managed geotourism activities are being considered by
A determination has been made under 324Q of the EPBC Act to protect the integrity of the site by not disclosing site location details. Due to the high market value of Ediacara fossils and the vulnerability of this site to fossil theft, DEH has provided significant funds to implement a range of monitored security measures (details can be provided upon request).
About 344ha, north west of Parachilna. The
precise location has not been disclosed, as provided for under Section 324Q of
the Environment Protection and Biodiversity
Conservation Act 1999.|
Arkaroola Wilderness Sanctuary
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Report Produced Fri Mar 14 09:20:26 2014