Tag Archives: South Australia

Fossil shells at Stansbury, South Australia, record a higher sealevel 125,000 years ago

Subsamples were taken of a collection of fossil shells recovered from a depth of around 3 m in trenches excavated in the Oyster Point Caravan Park by local contractors to improve drainage. Several of the fossils (Fig. 1) had been identified by SA Museum personnel and assigned to species including bivalves Katelysia scalarina and Sanguinolaria (Psammotellina) biradiata, and the large gastropod Turbo (Dinassovica) jourdani. All species are still living around the Australian coast, but these shells are clearly ancient and belong to a time when the coastal cliffs at Stansbury stood inland of the caravan park and the township and are now represented by the base of the hill that runs from the cemetery, northwards behind the town centre, and joins the current shore cliffs near the primary school oval. The seas, of which the fossil shells are a legacy, covered all of the lowland eastwards of these ancient cliffs. The cliffs themselves are in fact cut into much older marine deposits, as can be seen behind the jetty and elsewhere along the coast. These relate to the Tertiary period between 3 to 23 million years ago when much of Yorke Peninsula was inundated by sea.

Shell subsamples of two of the species (Katelysia scalarina and Sanguinolaria (Psammotellina) biradiata) were dated in the laboratories of the School of Earth & Environmental Sciences at the University of Wollongong by Professor Colin Murray-Wallace and his colleagues. They used a technique called Amino Acid Racemisation (AAR) and found that the shells are about 125,000 years old. Professor Murray-Wallace can be confident of this dating because he and his colleagues have much experience in determining the ages of ancient Quaternary coastlines of southern Australia and their fossils (see Further reading).

Sea levels 125,000 years ago (Fig. 2) were up to 2m above current sea level, as this time was part of an interglacial period (formally called the ‘Last Interglacial’) when ice in Antarctica and elsewhere had melted somewhat due to warmer global temperatures. This accounts for the encroachment of the seas into the embayment now occupied by much of Stansbury township, and the formation of the old cliff-line. The marine and coastal deposits generated at this time, and which occur widely around South Australian coasts, are referred to the Glanville Formation.

It might be of interest to note that several earth scientists, including Professor Murray-Wallace, have written a book on the coastal landscapes of South Australia. This is currently in press and should be available soon. It includes a chapter on the entire coast of Yorke Peninsula, including Stansbury. As well, a student from the School of Earth & Environmental Sciences at the University of Wollongong (Tsun-You Pan, visiting from Taiwan), and supervised by Professors Murray-Wallace and Bourman, has recently commenced a PhD research project on the Last Interglacial coasts and their deposits on southern Yorke Peninsula and may be able to report in future on his findings on these materials, including the Stansbury Caravan Park fossils.

Further reading

Bourman, R.P., Murray-Wallace, C.M. & Harvey, N. (2016, in press). Coastal Landscape of South Australia. University of Adelaide Press.

Ludbrook, N.H. (1984). Quaternary molluscs of South Australia. Handbook No. 9, 327pp. Department of Mines & Energy South Australia. (Government Printer: Adelaide).

Murray-Wallace, C.V., Bourman, R.P., Prescott, J.R., Williams, F, Price, D.M. & Belperio, A.P. (2010). Aminostratigraphy and thermoluminescence dating of coastal aeolianites and the later Quaternary history of a failed delta: The River Murray mouth region, South Australia. Quaternary Geochronology Vol. 5, pp28-49.

Zang, W-L, Cowley, W.M. & Fairclough, M. (2006). 1:250 000 Geological Series – Explanatory Notes. Maitland Special South Australia. Sheet S153-12 International Index. 62pp. Primary Industries and Resources SA (Government of South Australia).

Dr Tony Milnes, Earth Sciences, University of Adelaide

IMG_0272_cropped

Fig. 1 Assemblage of fossil shells found in excavation.

Fig 2

Fig. 2. Sea level curve for the past 130 000 years. Adapted from Lambeck and Chappell (2001). The thickness of the line of the curve is an expression of the degree of uncertainty of the calculated sea-levels. During the Last Glacial Maximum sea level was about 120 m lower than at present. The Last Interglacial warm period occurred about 130 000 to 120 000 years ago, when sea level was at least 2 m higher than at present. The present interglacial warm period (Stage 1) has existed for little more than the past 10 000 years. Source: Cann, J. (2014). Robe Geological trail. (Geological Society of Australia: South Australian Division).

 

A conversation with the community about Mining and environmental management

A context for Yorke Peninsula in South Australia

This article was the basis of a talk to a community group (‘Friends of Gulf St Vincent’) based in Adelaide, South Australia , which is committed to improving the ecology and amenity of the Gulf St Vincent biozone.  It was one of several talks given at a gathering of members of the Group and the local community in the Community Hall at Pine Point, a small village on the eastern coast of Yorke Peninsula.  The focus of the meeting was the possible impacts on Gulf St Vincent of an impending open-cut iron ore-copper-gold-uranium mine nearby (Hillside Mine), but broader issues of environmental impacts and controls were discussed.  Having earlier prepared and submitted a response to the Government regulator on the proposing Company’s submission of a mine and environmental management plan, my presentation at this meeting was broadly to overview mining and mine environmental management on Yorke Peninsula (in 20 minutes or so).

When faced with making a presentation on mining and mine environmental management, which is one of the issues that local communities are finding it increasingly difficult to deal with, I find it interesting and somewhat enlightening to take a step back and look at some history.  Community perspectives on industry, and especially coexisting with large-scale industry, has changed in Australia over the decades.  Perhaps with a historical perspective in mind, it might be possible to map a pathway forward to a productive and acceptable coexistence?

The following notes for my presentation are basically dot-points from a series of ‘slides’ which summarise the approach I’d taken in my presentation.  I’m not sure how it went.

Mining & agriculture started early

  • Both industries significantly changed landscapes.  Mining – local but intensive disturbance.  Agriculture – regionally extensive forest clearing but largely surface disturbance
  • Communities benefited from & adapted to both enterprises – but regulation, attitudes & circumstances changed with time
  • ‘Small’ farmer has gone; properties now amalgamated into large enterprises with fewer workers; rural towns & services have dwindled
  • ‘Mines’ neither larger nor necessarily closer to population centres now than in the past are being viewed as environmentally damaging & socially disruptive

Some history of mining on Yorke Peninsula

  • Copper mined from Wallaroo & Moonta from ~1860. Intermittent mining in 1930s & 1940s. Renewed exploration & from 1989 – 1994
  • Parara Mine (west of Ardrossan) operated for Cu-Au in the 1870s; the Hillside & Harts Mines were opened further south at about the same time in a similar geological setting
  • Salt mined & exported from Yorketown, Port Vincent & Edithburg from ~1874. Later developments at Price & Stenhouse Bay
  • Gypsum mined around Yorketown (1870s), Stenhouse Bay & Marion Bay (1890s) for export for plasterboard production
  • Calcrete mined almost everywhere for local building stone & lime mortar.  Lime kilns were very common & lime was exported to Adelaide.
  • Marine limestones mined for export as flux in Port Pirie Pb-Zn smelters from ~1896, mostly from quarries adjacent to ports
  • Cement produced & exported to Adelaide from Tertiary limestone at Stansbury from ~1913 & quarrying continues to this day at Klein Point
  • Dolomite produced from Cambrian limestone at Curramulka since ~1930s & from Ardrossan since 1948.  Exported as refractory for steel furnaces in Newcastle & Port Kembla
  • Construction sand now mined from a Tertiary paleochannel near Price for Adelaide building industry

Some history of agriculture

  • First agriculture ~1846 at Stansbury on an ‘Occupation license’
  • First pastoral lease in 1851 at Wallaroo
  • Agriculture on Yorke Peninsula as a whole expanded from ~1869 with land clearing & crop production.  Establishment & growth of port towns followed for export of goods; inland settlements & towns were established later
  • Poor yields during early days of agriculture addressed by superphosphate additions to soils starting ~1892. High demand for superphosphate.  Imported phosphate from Nauru (high Cd) & Christmas Island (high U) – widespread additions to South Australian soils
  • New barley crop varieties introduced ~1901
  • Extensive clearing of forest to produce additional agricultural land at ‘bottom end’ of the peninsula from 1950s – significant Cu & Mn deficiencies corrected by additives in superphosphate
  • Widespread modern use of ‘direct-drilling’ in croplands with increases in use of herbicides, pesticides, fertilisers

Getting back to mining – what about minerals exploration?

  • Basically, minerals exploration is controlled by geology. Main search areas are in the ancient basement rock complexes.  Gawler Craton – Olympic Dam orebody in central South Australia, Wallaroo-Moonta mines in northwestern Yorke Peninsula; Curnamona Province in northwestern South Australia – Broken Hill mines.

Old crustal elements form the foundations of South Australia and some of the State’s largest orebodies are found in them.  (Map from Preiss W V et al. 2002 MESA Journal 27, 39-53; http://bit.ly/1Tt4KZI)  Cratons

  • In Australia all mineral deposits are owned by the Crown & the Government approves applications to explore (& possibly later to mine) – on conditions

Exploration

  • Much exploration & analysis utilises remote sensing data – well before field work starts
  • Exploration leases are granted on application to Government
  • Drilling of target areas follows much deliberation, assessment, sampling & analysis (high costs)
  • Success in finding an economic orebody is very lowAirborne magnetics give clear indications of the geological makeup and structure (‘bones’) of the land at various depths beneath the surface (red = most magnetic rock; blue = least magnetic rocks). (Map from SARIG)

Airborne magnetics give clear indications of the geological makeup and structure (‘bones’) of the land at various depths beneath the surface (red = most magnetic rock; blue = least magnetic rocks). (Map from SARIG)

 

 

Radiometric K

Airborne radiometrics provide unique information about the distribution of radioactive elements (K,Th,U) in surface rocks and soils from gamma ray signals (red = most potassium; blue = least potassium). (Map from SARIG)

Regulations

  • If, after exploration, an orebody is discovered and assessed to be ‘economic’, Government approves (or not) an application to mine on conditions based on submission of a ‘comprehensive’ formal Proposal or Plan
  • Legislation drives the process & the outcomes: Mineral Resources Division (Department of State Development) in South Australia is the regulator
  • Consultation with landowners & communities (particularly at the exploration stage) can be inadequate.  Community angst leading to ‘outrage’ is a common consequence
  • Environmental management guidelines (& community expectations) can be ‘downplayed’ in favour of ‘public good’
  • Company (& shareholders), Government (through royalties & taxes) & Community (employment, local Company spend, services) can all benefit from a mining operation. What about landowners?  How is best to benefit neighbouring landholders?
  • BUT legislation (& regulation) is generally inadequate in terms of environmental management & rehabilitation (post-mining) – can lead to significant environmental legacy
  • Information about what can & can’t be ‘done’ should be readily available & clearly explained to communities.  How? By whom?
  • Community lobby can change legislation: best practice environmental management ‘guidelines’ should become ‘requirements’?
  • Cost of mining projects must include the full cost of rehabilitation of project areas to something like that existing pre-mining according to best practice guidelines – not currently the case .  Many mining projects would not proceed if this was the case!
  • Mining companies & legislators should include community representatives on site-specific environmental management committees that operate for the term of the project and have ‘teeth’?
  • Community groups must remain active & vigilant?

Summary

  • Historically, mining has predated agriculture & other enterprises to ‘kick-start’ local economies, usually in ‘outback’ areas
  • In time, agriculture & pastoral pursuits generally ‘subsume’ land after mining ceases, even though there are on-going environmental legacies
  • Different forms of community development attach to mining & agriculture – community attitudes/perspectives change (and will continue to do so)
  • Legislation drives environmental regulation – community attitudes & perspectives can help to change legislation
  • Knowledge is key – monitoring & acceptance (or not) of impacts of any enterprise on local & regional landscapes ultimately falls to the community
  • Change is inevitable – alertness, communication, regulation, adaptability, science all help

Some mining operations currently on southern Yorke Peninsula

Ardrossan dolomite quarry & port facility  Ardrossan

 

 

 

  

Klein Point limestone quarry & port operations  Klein Point

 

 

 

 

Stenhouse Bay gypsum operations  Stenhouse Bay

 

 

 

 

Price salt pans  Price saltpans

 

 

 

 

Dr A R Milnes