Category Archives: Geosciences education

The beach cliffs north of Stansbury

North of Stansbury on Yorke Peninsula (South Australia), towards Port Vincent, there is an interesting hike along the beach at low tide.  Prominent cliffs of yellowish fossiliferous limestone overlain by reddish sand and mottled clay are in places capped by white carbonate-rich silts and hard limestone called ‘calcrete’ (1).  The cliffs are up to 20m high except where broken in a few places by gullies that mark once active, short streams.  At high tide the sea laps at and erodes the base of the cliffs across a shore platform cut into the limestone. Version 2

The limestone beds (Port Vincent Limestone) were deposited in Oligocene to Miocene times, roughly 20-30 million years ago.  The overlying reddish sands and clays (Hindmarsh Clay) are probably around 700,000 years old (Pleistocene age) and the white carbonate (lime) capping is even younger.

At the Stansbury jetty, the cliffs are mostly of Port Vincent Limestone.  The original bedding in the limestone is outlined in places by thin rubbly layers and elsewhere by shell-rich beds.  The limestone was deposited in shallow seas that once occupied the St Vincent Basin. Conspicuous amongst the fossils are whole-shell sea-urchins (echinoderms), bivalves (clams and oysters) and bryozoa in a sandy matrix that is largely made of shell fragments (4).  The cliffs show spectacular evidence of former caves, sinkholes, pipes and other solution features: these are obvious because they are filled with mottled green, yellow and red sandy clays (2, 3).   Undercutting by the sea has progressively collapsed the limestone to expose these structures and in places wash out the clays.  The caves and pipes characteristically have smooth surfaces dating from a time when lime-rich solutions seeping over their walls precipitated calcite on evaporation. Version 2

Version 2

Version 2

In the section from Beach Point (Long Beach) northwards, the Port Vincent Limestone is overlain by Hindmarsh Clay, a thick band of mottled green-yellow clays and deep red sandy clays.  In contrast to the marine origin of the limestones, these were deposited during the Pleistocene in fluvial environments.  The boundary between the two formations is important as it represents a large time break of several million years, during which the seas retreated from St Vincent Gulf to well south of Kangaroo Island.  As this was happening, in the Late Tertiary period, the changing conditions exposed the limestones at the landsurface and subjected them to erosion, weathering and dissolution to generate a significant karst (caves, sinkholes, pipes, and the like) landscape.  Major riverine and lake environments later became established in the former gulf.  The river systems drained highlands to the north and generated widespread alluvial and lacustrine deposits of sand and clays over the karst limestone, filling the caves and sinkholes to produce the remnants we see in the cliffs today.

It’s interesting to speculate as to whether the remains of any fauna (including megafauna) occur within this cave and sinkhole landscape.  It did, after all, form at about the same time as the extensive cave systems in the limestones of the South East and the Nullarbor which contain abundant mammalian and other fossils.

A feature of the Hindmarsh Clay is the occurrence in places of white bands of the mineral alunite (potassium aluminium sulfate).  Towards the northern end of Long Beach it was sufficiently abundant for local entrepreneurs to begin to mine it to produce potassium sulfate fertilizer (according to a report by RL Jack, Assistant Government Geologist, in 1918),  which was in short supply during the First World War, but the venture failed.   Remnants of mining operations can still be seen at the base of the cliffs behind sand dunes (5).  The alunite was formed from a reaction between acid groundwater and potassic clays in the sediments.  The process in detail is unclear, but the occurrence of alunite in superposed near-horizonal seams suggests that appropriate conditions may have related to flow of local acid groundwater.Version 2

Above the Hindmarsh Clay in most of the cliff-line is a ‘blanket’ of younger Pleistocene lime deposits.  These consist of unconsolidated silts with interlayers of hardened calcrete.  The youngest calcrete is exposed as sheets over large areas of the landsurface on this part of Yorke Peninsula, and was exploited in earlier days for the local production of quicklime.  It remains an impediment to cropping but is progressively being crushed and disaggregated by farmers using heavyweight rollers hauled behind large tractors.  The unconsolidated carbonate silts are considered to be a loess-like aeolian deposits whereas the calcrete bands are likely to represent the remnants of ancient soils that formed at successively younger times.

What else can we note about the geology of the Stansbury cliffs?

Projecting the top of the cliffs seawards provides an indication of the former extent of the Pleistocene landscape that has now been disrupted and incised as the St Vincent ‘valley’ was drowned by rising seas.

Fallen blocks accumulated at the base of the cliffs is the result of mass collapse of limestone and calcrete in the cliffs caused by back-wasting under the attack of waves.  Some rock fragments are very large; others are small and part of a lag concentrated by tides at the back of beach.  Many are angular, which indicates that they have relatively recently fallen from the cliff; some are rounded and smoothed which indicates that they have been washed around in the surf zone for a long period of time.   It’s interesting to speculate about the time that it takes the cliff to retreat under the attack of the rising sea.  Only observations over the long-term (mapping of fallen blocks or reference to old photographs to compare with the present) might answer this question.  However, most cliff erosion is likely to take place at comparatively rare times of severe storms and powerful wave and wind attack, whereas little change occurs under usual weather conditions.

The cliffs in some places are coated with a ‘wash’ of sediment from higher in the sequence, and this sometimes obscures the geology and makes it difficult to pinpoint breaks in the rock sequence. This coating varies from a thin surface veneer to substantial talus deposits, and usually occurs in places where the cliff is less exposed to wind and waves.  As well, in places, the red sand and clay fill in the old caves and pipes has spilled out from the cliffs where erosion has exposed them.

Collapsing masses of rock, spilling of sands and clays from less coherent deposits, breaking apart and exposure of karst features, and wash over cliff surfaces, are all components of cliff retreat in this region.

It’s interesting that the cliffline can be traced from actively eroding beach cliffs north of the jetty at Stansbury to a subdued hillslope at the back of the town to beach cliffs again south of the cemetery. The townsite is actually an embayment that was filled by shallow water shelly limestones (deposited around 10,000 years ago in seas that were at a slightly higher level than today) and covered by more recent sand dunes.  It seems to have been a quirk of nature that preserved the embayment, in much the same way that winds, tides and seawater circulation on this eastern side of the gulf produced distinctive, recurved sand and mud spits that protect other bays like Stansbury.

Further reading.

RP Bourman, CV Murray-Wallace, N Harvey (2016)  Coastal Landscapes of South Australia.  (University of Adelaide Press: Adelaide).  423pp.

AR Crawford (1965)  The Geology of Yorke Peninsula.  Bulletin No. 39.  Department of Mines, Geological Survey of South Australia. 139pp.

RL Jack (1918)  Alunite deposits, Section A. Hundred of RamsayInSouth Australia Department of Mines, Mining Review No. 28 for the half-year ended June 30th, 1918.  pp51-53.

AR Milnes, JT Hutton (1983)  Calcretes in Australia – a Review.  In ‘Soils: an Australian Viewpoint’, Chapter 10, 119-162. (CSIRO, Melbourne/Academic Press, London).

WJ Stuart (1970)  The Cainozoic stratigraphy of the eastern coastal area of Yorke Peninsula, South Australia.  Transactions of the Royal Society of South Australia 94, 151-178.

Dr Tony Milnes – Earth Sciences, University of Adelaide

Sir Douglas Mawson, University of Adelaide

Overview

Douglas Mawson was born on May 5, 1882 at Shipley in Yorkshire and migrated in 1884 to Australia with his parents Robert and Margaret and older brother William.  From 1895 to 1898, William and Douglas attended Fort Street Model Public School in Sydney, one of the best public secondary schools in Australia.  From 1899 to 1901, Douglas Mawson studied Mining Engineering at the University of Sydney, graduating on April 19, 1902.  Mawson’s best results were in geology under the influence of TW Edgeworth David, the charismatic Professor of Geology at the time. This was the start of a lifelong friendship and professional association, which ended only on David’s death on August 28, 1934 (Corbett 1998, 2000).

In 1902 Mawson commenced a Bachelor of Science degree, majoring in geology.  This was interrupted by him spending several months (April to September 1903) studying the geology of the New Hebrides (modern Vanuatu) at the behest of Edgeworth David.  Mawson graduated with a Bachelor of Science in early 1905 and commenced an appointment as Lecturer in Mineralogy and Petrology at the University of Adelaide on March 1, 1905.  The only other geologist at Adelaide University at the time was 60 year old Walter Howchin.

After arrival in Adelaide, Mawson was very active and in particular studied the geology of the Broken Hill area and the neighbouring Olary area in South Australia.  Here Mawson found Precambrian rocks that he considered to have been deposited by glacial action.  He wished to see modern glacial activity and in late 1907 contacted Edgeworth David, and through him, Ernest Shackleton, the leader of the 1907-1909 British Antarctic Expedition (BAE).  As a result, he was appointed as physicist to the expedition.  The BAE was based on Ross Island.  Highlights of this expedition for Mawson were participation in the first ascent of Antarctica’s only active volcano, the 3794m high Mt Erebus, and membership of the first party (with Edgeworth David and Alistair Mackay) to reach the vicinity of the South Magnetic Pole.  David and Mawson returned to Australia as heroes.

Later in 1909, Mawson found time to continue his Broken Hill studies and completed his doctorate before the end of the year.  While working in Broken Hill, Mawson met Paquita Delprat, a daughter of Guillaume Delprat, the General Manager of BHP, whom he later married.  Mawson visited London in late 1909 and unsuccessfully tried to persuade Scott to land him at Cape Adare, in order to study the geology of the area.  He then organised the Australasian Antarctic Expedition (AAE), the story of which has been well documented by Mawson (1964), Ayres (1999), Hall (2000), Fitzsimons (2011) and particularly by Riffenburgh (2011) who gives the most comprehensive account.  The AAE was most notable for Mawson surviving and struggling back to the base at Commonwealth Bay after the deaths of Belgrave Ninnis and Xavier Mertz, his sledging companions on the Far Eastern Party.  The boat had already left and Mawson was obliged to stay in Antarctica for another twelve months with six members of his party, led by Cecil Madigan, who had stayed behind.  As part of the AAE, bases were also established on Macquarie Island and the Shackleton Ice Shelf.  The AAE saw the first use of radio communications with Antarctica.

Mawson was knighted in 1914. He was in the UK from 1916 as part of the war effort, returning to Adelaide in April 1919 where he was appointed Professor of Geology and Mineralogy at the University of Adelaide in 1921, a position he held until his retirement in 1952.  For the next few years Mawson was involved in raising funds to pay off the debts of the AAE and in organising the publication of the scientific reports resulting from the expedition.  He was an enthusiastic field geologist and did considerable field work in the Broken Hill/Olary and Flinders Ranges areas, usually accompanied by students.

In the summers of 1929-30 and 1930-31, Mawson led the ship-based British, Australian and New Zealand Antarctic Research Expedition (BANZARE) using the Discovery, the ship used by Scott in his first expedition in 1901-04.  This was a largely marine science, oceanography and biology expedition, but included landing on Heard Island and a visit to Mawson’s old headquarters at Commonwealth Bay.  On the second voyage, Mawson claimed formal possession of King George V Land on behalf of Britain.  This is the basis of the present Australian claim to what is termed the Australian Antarctic Territory, which represents about 40% of Antarctica.

Mawson continued his field work in the Flinders Ranges in the 1930s and 1940s.  He was a driving force in the establishment of ANARE (Australian National Antarctic Research Expeditions) that still runs the Australian Antarctic research activities.  He continued to publish research papers until his death on October 14, 1958.

Memorabilia

The University of Adelaide and the adjacent South Australian Museum have displays where Mawson memorabilia can be viewed.

The Tate Museum in the Mawson Laboratories in the University at the corner of Frome Road and Victoria Drive has a display showcasing Mawson’s Antarctic activities on its southern wall.  Some of the rocks collected on the Australasian Antarctic Expedition of 1911-14 are housed in the display cases and there is a substantial further collection in the basement crypt archive (where some sample boxes containing these specimens are as yet unopened).  One of the AAE sledges is on the north wall of the Tate Museum.

On North Terrace, at the entrance to the University just west of the Bonython Building, there is a bust of Mawson which was unveiled in 1982 on the occasion of the Fourth International Symposium on Antarctic Earth Sciences, held in Adelaide to commemorate the centenary of Mawson’s birth.  At the foot of the bust are two large boulders: one is charnockite from near Mawson Station in Antarctica and the other is pegmatite from Arkaroola in the northern Flinders Ranges.

A recently revamped Australian Polar Exhibit at the South Australian Museum, just to the west along North Terrace, deals with Mawson’s three visits to Antarctica, as well as his work in the Flinders Ranges.  There are numerous artifacts from this work as well as some general information on Antarctica.  There is also reference to the other two major Australian polar explorers from the pre-World War II era, namely Hubert Wilkins and John Rymill, both of whom were born in South Australia.

Selected references

  • Ayres, P, 1999. Mawson. A life. (The Miegunyah Press, Carlton South).
  • Cooper, BJ & Jago, JB, 2007. Mawson’s earliest (1906) report on the geology of the Flinders Ranges. Transactions of the Royal Society of South Australia, 132, 167-174.
  • Corbett, DWP, 1998. Douglas Mawson: The geologist as explorer. Records of the SouthAustralian Museum, 30,107-136.
  • Corbett, DWP, 2000. A staunch but testing friendship: Douglas Mawson and T.W.Edgeworth David. Records of the South Australian Museum, 33,49-70.
  • Fitzsimons, P, 2011. Mawson and the Ice Men of the Heroic Age: Scott, Shackleton andAmundsen. (William Heinemann, North Sydney).
  • Hall, L, 2000. Douglas Mawson: The life of an explorer. (New Holland, Sydney).
  • Jacka, FJ, 1986. Mawson, Sir Douglas (1882-1958). Australian Dictionary of Biography. (http://adb.anu.edu.au/biography/mawson-sir-douglas-7531).
  • Jago, JB & Pharaoh, MD, 2016. Pre-Antarctic Mawson in South Australia and western New South Wales. Transactions of the Royal Society of South Australia, 140, 107-128.
  • Jago, JB, Pharaoh, MD & Wilson-Roberts, CL, 2005. Douglas Mawson’s first major geological expedition: The New Hebrides, 1903. Earth Sciences History, 24,93-111.
  • Mawson, D, 1915. The Home of the Blizzard. 2 volumes.  (William Heinemann, London).
  • Mawson, P, 1964. Mawson of the Antarctic.  (Longmans, London).
  • Riffenburgh, B, 2011. Aurora. Douglas Mawson and the Australian Antarctic Expedition1911-14. (The Erskine Press, Norwich).
  • The Adelie Blizzard: Mawson’s Forgotten Newspaper, 1913, edited by Archie McLean. Reproduced by The Friends of the State Library of South Australia, 2010.

Author:  Professor Jim Jago, School of Natural and Built Environments, University of South Australia. jim.jago@unisa.edu.au

Gulf St Vincent & Adelaide beaches

Over the last million years in southern Australia, sea levels have fluctuated between about 120m below present sea level, during the Ice Ages, to about 2m above during the interglacials.  As humans first arrived in Australia more than 50,000 years ago, the sea level fluctuated between 60 and 40m below present, and vast coastal areas were exposed for settlement.  Gulf St Vincent has a maximum depth of 40m so, during those times, it had the form of a flat landscape of alluvial plains veneered with calcrete and covered by thin sandy soils and sporadic desert dunes gently sloping towards a central oblong saline swamp (Fig. 1).

Around 30,000 years ago the Earth plunged into a severe Ice Age that lasted until about 15,000 years ago, with sea levels dropping to 120m below present.  A warming climate then caused rising sea levels, so that by around 9,700 years ago the sea encroached into the land to form the Gulf (Fig. 2).  Continued climate warming and further sea level rise progressively filled the Gulf.  The warm shallow seas enabled prolific growth of algae and marine grasses that were nurseries to a rich ecology of fish, shellfish, starfish, sponges, calcareous algae and some corals.  Sand-sized foraminifera were abundant, especially in the nearshore and intertidal zones (corresponding to the mangrove-rich areas north of Adelaide).

By around 6,500 years ago the sea had reached its present level and the Gulf achieved its current shape.  Abundant shells and shell grit were deposited to form a meter-thick veneer of calcareous sediment covering the now drowned landscape.  Predominant south-southwesterly winds created waves that eroded these sediments, for example around Port Norlunga and Maslins Beach, and quartz sand winnowed from them mixed together with more recent shell grit to create the modern beaches (Figs 3, 4).  Some quartz sands came from more ancient deposits that are now exposed at Hallett Cove.

Frequent southwesterly storms drove coastal sands northward from Marino Rocks and Glenelg to form a coastal dune series that enclosed the Patawalunga and Westlake depression.  This wave-dominant dune system continued to grow northward creating the present Le Fevre Peninsula where around 10m of sand has accumulated (Fig. 5).

European settlement since 1836 has altered the coastal zone by building on or removing most sand dunes, thus allowing storms to attack roads and residences. Placement of rocky rip-rap with the aim of protecting the shoreline has in fact increased wave turbulence and lowered the beach profile by removing additional sand.  Replenishment of beach sands to maintain amenity is a continuing Government-funded activity.  Tennyson Dunes is one of a few tiny remnants that provide a glimpse of the original Adelaide metropolitan coastline.

References

Bourman RP, Murray-Wallace CV, Harvey N. 2016. Coastal Landscapes of South Australia.Available as a free ebook from www.adelaide.edu.au/press.

Fuller MK, Gostin VA. 2008. Recent coarse biogenic sediments of Gulf St Vincent.InSA Shepherd et al. (eds) Natural History of Gulf St Vincent.  Ch.3 , 29-37. (Royal Society of South Australia).

Harvey N, Belperio AP, Bourman RP. 2001.  Late Quaternary sea-levels, climate change and South Australian coastal geology.  InV Gostin (ed.) Gondwana to Greenhouse: Australian Environmental Geoscience. Geol. Soc. Aust. Spec. Publ. 21, 201-213.  (Geological Society of Australia: Sydney).

James NP, Bone Y. 2011. Neritic Carbonate Sediments in a Temperate Realm, (Springer Science+Business Media).

www.tennyson.org.au

Author: Dr VA Gostin

Paradigms in astronomy & Earth history are not absolute

Not a week passes that a new astronomical discovery is announced in the popular as well as the scientific press.  Our vision and appreciation of our living and cosmic environment is continually changing.  Old, long-held views – for example, that our solar system is the only example of planetary systems – continue to be replaced by new ideas and concepts.  During the 1960s and 1970s, we witnessed a similar paradigm shift from the notion of a very solid, relatively stable Earth, on which oceans and continents would periodically subside or emerge from beneath sea-level, to a vigorous Plate-Tectonic Earth, on which oceans are continually created and removed.  We now know that light and buoyant continents are essentially carried as ‘passengers’ on the ever-circulating, dense, underlying mantle.  It took decades before most (but not all) earth scientists were convinced by the evidence for this concept.

New astronomical techniques

Recent astronomical discoveries that challenge former theories are particularly fascinating.  Looking out into the far reaches of our Universe, researchers have now detected a radio signal from the first stars formed.  Because such distant red-shift signals fall in the FM radio electromagnetic spectrum, Judd Bowman, of the Arizona State University’s discovery team, had to use the Murchison Radio-astronomy Observatory in the ultra-quiet region of Western Australia, to detect the weak signal.  This discovery, as indeed most astronomical information, comes to us via exploration of the whole electromagnetic spectrum.

In contrast, a whole new way of exploring the universe by observing gravitational waves (first reported in April 2016) has recently been proved.  Andrew Grant has called this the beginning of multi-messenger astronomy (Physics Today, October 2017).  Seconds after the gravity wave recorders (LIGO and VIRGO) detected gravitational waves, the Fermi Gamma-Ray Space Telescope spotted a gamma-ray burst.  Many observatoriesconfirmed this event. The observations suggest that gamma-ray bursts result from colliding ultra-dense neutron stars, the enormous energy release from which is sufficient to create heavy elements like gold and uranium via the fusion of lighter elements.

Colliding-galaxies

This stunning image, taken by the Hubble Space Telescope, shows the individual galaxies UGC 1810 (right) and UGC 1813 (left) in the process of colliding. Together, this pair of interacting galaxies is known as Arp273. Image courtesy of NASA/ESA/HHT

In the past year, there have also been breakthroughs in the study of cosmic rays that continually bombard the earth.  While most are light protons, some are ultra-high energy cosmic rays made of iron nucleii that may originate from supermassive black holes in the centre of distant galaxies.  In addition to cosmic rays, our planet is immersed in charged particles emanating from the Sun in what is termed the solar wind.  This reacts with the Earth’s magnetic field and creates numerous transitory phenomena including the aurorae, sprites and lightning.  The solar wind controls spaceweather and climate.  On the other hand, retention of the Earth’s atmosphere is generally attributed to theplanet’s strong magnetic field which prevents widespread stripping of the volatile gasses by the solar wind.  A review of the Earth’s electromagnetic environment was published by Catherine Constable in 2016 (Surveys in Geophysics37, p27-45).

When some massive stars are at the end of their life cycle they become supernovae that violently explode, expelling gas at high speed into space.  These explosions are strong enough to hurl matter across vast distances into neighbouring galaxies.  Our own Milky Way galaxy has apparently grown significantly by capturing material from its satellite galaxies, namely the Small and Large Magellanic Clouds (A. Woodward, New Scientist, August 2017). We clearly live in a complex interactive universe, but the time scales are vast in comparison to the brevity of human experience.

Collapse of a single planetary paradigm

The old paradigm of planetary origins based on our Solar System has collapsed with the discovery of hundreds of other planets with very different orbits.  An article by Ann Finkbeiner (Planets in Chaos: Nature, July 2014) describes this astronomical puzzle.  Planets in their early years collided, interacted, migrated and grew in size, before ultimately settling into some relatively stable arrangement. This turbulent and chaotic impact history during the early assemblage of planets resulted in the expulsion of some planets into the cold emptiness of space, away from their parent stars.  Some stars, like our own Sun, have large families of planets.  As of December 2017, researchers have identified 3,567 exoplanets.  Two telescopes planned to be launched in 2018 will search for signs of other planets by observing their crossings in front of parent stars (J.N. Winn, Scientific American, March 2018, p26-33).

Meteors and impacts on Earth

Recent observations confirm that meteorite impact on Earth is a dynamic process that continues and directly influences our environment.  The planet is continually showered by meteors of various sizes from microscopic space dust and visible sand-sized meteorite grains, up to fragments, some kilometers in diameter, of rarer asteroids or comets.

Some asteroids with unusual fractured shapes and compositions have recently whizzed past our planet on hyperbolic (i.e. non-returning) orbits, and continued onto other stellar rendezvous (K. Cooper, New Scientist, February 2018).  The estimated number of such interstellar objects may be in the thousands.  More relevant of course, have been those visitors that have made direct hits on Earth. Much of Earth’s history since Proterozoic times has in fact been shaped by catastrophic meteorite impacts that have triggered mass extinctions of living creatures and other biological effects.  The immense impact some 63 million years ago that spelt the extinction of dinosaurs, as well as ammonites and other marine creatures, is well known, as perhaps is the atmospheric explosion at Tunguska, in central Siberia only a century ago (1908).  Recognition of the importance of major meteorite impacts on Earth history has been yet another paradigm shift in our understanding.

A cometary catastrophe

Less well known is the discovery that fragments of a disintegrating ~100km-diameter comet collided with the Earth some 12,800 years ago in what is known as the Younger Dryas period (named after a signature Arctic flower).  The collision triggered a rapid return to glacial conditions which lasted about 1,400 years, interrupting the gradual warming of the planet after the Last Glacial Maximum around 20,000 years ago.  In a two-part publication in 2018, Wendy Wolbach (and 31 co-authors) presented a detailed analysis of evidence of this most unusual climatic episode gathered over the last decade (W.S. Wolbach et al.,Journal of Geology126, p165-184 & p185-205).  Data was gathered from ice-cores in Greenland, Russia and Antarctica as well as from lake, marine and terrestrial sediments.  Contemporaneous layers of charcoal and dust in these geographically dispersed cores confirm this cosmic impact event.  These specific layers are enriched in platinum and other impact-related elements.  They also contain glassy spherules and nano-diamonds, and are anomalously high in ammonia, nitrate, and other compounds that represent a major period of extensive biomass burning.  Sea levels rose a few metres due to major melting of the North American Ice Cap and this surge of fresh water disturbed the oceanic circulation that began a period of cooling.

YDB field

YDB = Younger Dryas boundary field. graphic from C.R. Kinzie et al. The Journal of Geology, 2014, v122, p475–506.

Evidence points to numerous fragments of a disintegrating comet detonating above and/or colliding with ice-sheets, oceans, and land on at least four continents centred on North America.  The radiant and thermal energy from multiple explosions triggered extensive wildfires that are estimated to have burned about 10% of the planet’s biomass, considerably more than that accompanying the meteorite impact that caused the demise of the dinosaurs.  The burning created long-lived atmospheric soot, blocking most sunlight and creating an ‘impact winter’ and acid rain.  The reduced vegetation caused a major crisis in the ecosystem and may have contributed to many megafaunal extinctions including mammoths, mastodons, ground sloths and American horses, along with many birds and smaller mammals.  Human population declined for about a thousand years and the demise of the Clovis hunters ensued.  This synchronicity of multiple events makes the Younger Dryas interval one of the most unusual climatic/ecological episodes during the last two million years.  It also raises the importance of supporting the Near Earth Asteroid Survey in defence of future serious impacts on our planet.

Our changing paradigms

The rapid acquisition of new and exciting knowledge about astronomy and Earth history requires paradigm shifts in our thinking and interpretation.  We should always be prepared for new scientific observations and revelations and continue to adapt our ideas and concepts to better explain our cosmic and earthly environments.

Dr Vic Gostin

Tate Museum attracts young scientists

The Tate Museum, at the University of Adelaide, is considered to be the largest and best Australian university geology museum.  Although established in the 1880s by Professor Ralph Tate, the foundation Elder Professor of Natural Sciences at the University (1875 – 1901), the Museum was named in his honour in 1902, after his death.  It was moved into its current location in the Department of Earth Sciences’ Mawson Laboratories in the early 1950s.  The history of the Museum, which is an important part of University Collections, has been well documented by Dr Barbara Kidman.

The extensive assemblage of minerals, meteorites, Antarctic rocks and memorabilia relating to Sir Douglas Mawson’s expeditions, as well as rocks and fossils that record important aspects of Australian and South Australian geology, are presently being catalogued and recorded using digital tools not available in past decades.  New displays are also being designed.  Much of the work is being undertaken by volunteers in lieu of a Museum Curator, a position that has not existed in the Mawson Laboratories for many years.

DSCN2140

Tate Museum with specimens housed in cabinets  matching those made for the first-generation of the museum in the 1880s.

Visitors to the Museum, which occupies a ‘foyer’ to the Mawson Lecture Theatre, include University students attending lectures, attendees at Learned Society meetings, parties of school students and off-the-street visitors. All express delight that a historical Museum such as this exists.  Research students and staff from within the University, and also overseas, are surprised at the breadth of the mineral and meteorite collections, and occasionally request subsamples for specific research purposes.  In this manner, the Museum has an ongoing role in assisting new research and, at the same time, receiving new data and information about its specimens.

Visits by parties of school students are especially noteworthy.  On Tuesday 8th May, twenty enthusiastic young (7-12years) Science Club students from the Woodcroft State School visited the Museum.  Dr Vic Gostin, who often hosts visitors to the Museum, talked to them about the work of Professor Ralph Tate, who studied and maintained collections of Type Specimens of molluscs (including fossil forms) found in South Australia.  As well, his analysis of the ancient glacial features on Fleurieu Peninsula eventually led to a total paradigm shift to ‘Plate Tectonic’ theory.  The students were encouraged to visit the Hallett Cove Conservation Park to view the scientific evidence.  Dr Gostin also pointed out the pioneering exploratory work of Sir Douglas Mawson in Antarctica, as illustrated by displays of his Antarctic specimens and memorabilia.

A special display of hand-sized meteorites and Australites enabled the students to ask questions and become aware of the asteroid/space connection.  Finally, they were allowed to handle and be photographed with the Nakhla Martian meteorite and so, in great excitement, ‘got their hands on another planet’!

The 90-minute visit of this keen group of Science Club students was peppered with exclamations and insightful questions, including many about the variety of spectacular minerals on display.

The Tate Museum and its collections are recognised by many visitors as an important University asset and scientists like Dr Gostin, who know of its history, say that it generates great interest and provides encouragement for current and potential future earth scientists.

Additional reading:

Kidman, B P (2015).  Ralph Tate, his Natural History Museum at the University of Adelaide and the ‘Tate Museum’.  Historical Records of Australian Science, 2015, 101-121. (CSIRO Publishing).

Dr Tony Milnes, Dr Vic Gostin

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