Overview: Pictures of Time Beneath examines three celebrated heritage landscapes: Adelaide’s Hallett Cove, Lake Callabonna in the far north of South Australia, and the World Heritage listed Willandra Lakes Region of New South Wales. It offers philosophical insights into significant issues of heritage management, our relationship with Australian landscapes, and an original perspective on our understanding of place, time, nation and science.
Glaciers in Adelaide, cow-sized wombats, monster kangaroos, desert dunes littered with freshwater mussels, ancient oases and inland seas: a diverse group of deep-time imaginings is the subject of this ground-breaking book. Ideas about a deep past in Australia are central to broader issues of identity, belonging, uniqueness, legitimacy and intellectual community. This journey through Australia’s natural histories examines the way landscapes and landforms are interpreted to realise certain visions of the land, the nation and the past in the context of contemporary notions of geological heritage, cultural property, cultural identity and antiquity.
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| Pictures of Time Beneath Science, Heritage and the Uses of the Deep Past by Kirsty Douglas Book |
Pictures of Time Beneath Science, Heritage and the Uses of the Deep Past by Kirsty Douglas Book Read Online Chapter One
PRESERVATION AND CHANGE IN AN ‘OUTDOOR MUSEUM’: A MODERN DIORAMA
Geological exegesis lends itself to scene-by-scene presentation. These can be visual or verbal representations, but importantly, they impose a narrative structure on the incomplete and fractured material remains of the deep past. This sleight of hand invests broken sequences of fragmented and twisted earth and rock with a determinism that simplifies and obscures both the degree of sophisticated supposition and practical science which produce geological narrative. It is a useful cognitive tool.
The present landscape at Hallett Cove is old. It has been forming and changing for more than 600 million years. But in one small section south of Waterfall Creek is represented all of the events in the following diorama summarised visually in Figure 7, and described in the following panels.1
Panel 1
The first panel represents the oldest rocks exposed in the park: the red mauve siltstones of the Brachina Formation at Black Cliff. These are vestiges of the formerly flat-lying sands and silts of a tidal flat on a continental shelf about 550 million years ago. Australia was then part of what is called the Gondwanan supercontinent along with the lands that now make up Antarctica, South America, Africa, Madagascar, New Zealand and India. For millions of years previously sediments eroded from the low land to the west into a series of shallow seas – the large sedimentary basin now known as the Adelaide Geosyncline – which might have extended from the present position of Kangaroo Island, beyond Lake Eyre, into Central Australia. In the process of filling the depressions, these sediments subsided under their own weight. As their water content reduced, sands in shallower water became the sandstones and in deeper water silts and muds became the siltstones and shales of the tidal flat. Eventually over the next 100 million years, the deeply buried sediments were altered by heat and pressure into the hard rock exposed at the cliff line today. Life had not yet colonised the rocky land, but algae and multicelled organisms like jellyfish appeared in the sea.
Panel 2
The Black Cliff sediments are also the modern expression of my second panel (see Figure 8). They are the eroded remnant of a colossal mountain range, similar to the modern Himalayas, which formed in the Ordovician period, some 480 million years ago. The land that would become South Australia was north of the equator. Large-scale crustal movements buckled the sediments of the Adelaide Geosyncline (Panel 1) in a north-westerly direction. They were folded and uplifted into a massive chain sometimes referred to as the Delamerian Mountains after the Delamerian Orogeny that formed them (Figure 8). This chain stretched south into Antarctica and north into central Australia. Life continued to diversify during the preceding Cambrian period and, although there was no life on land yet, the oceans contained trilobites, jellyfish, molluscs and sponges.
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Figure 7: Geological section, Hallett Cove Conservation Park. Solid white lines represent major unconformable boundaries, dashed lines in the lower half of the image outline folds of the Delamerian Orogeny. (Photograph K. Douglas)
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Figure 8: Shore platforms at Black Cliff showing folding. (Photograph K. Douglas)
Panel 3
My third panel – a diorama in itself – is represented at Hallett Cove by an absence. While grounded very literally in the evidence provided in the earth and rocks, geological exegesis also relies on concepts as esoteric as unconformities. An unconformity functions rather like parentheses. It is a contact between sediments of different ages that delimits a period of non-deposition or erosion. It is Charles Darwin’s ‘history of the world imperfectly kept’. This particular unconformity defines the base of a palaeovalley and represents more than 200 million years of landscape evolution. The Delamerian Mountains were intensely eroded, leaving no hint of these changes as they affected the cove. But elsewhere in Gondwana, central Australia was covered by shallow sea. Fossils of bivalves, crinoids, graptolites and the first jawless fish appear in mid to late Ordovician sediments. Vascular plants colonised the land. There was volcanic activity on the ‘east coast’, as eastern Australia formed during the Silurian. The first jawed fish appeared and diversified in Devonian seas, as did tree-sized club mosses on land. Forests appeared in swampy areas. Early amphibians and insects inhabited the land. Australia moved south of the equator. The Carboniferous began warmly, but cooled as Gondwana moved across the South Pole. Conifers evolved and insects took to the air. Glaciers began to develop.
Panel 4
The fourth panel is once more represented in the rocks at Hallett Cove in the wide band of glacial sediments which fill the palaeovalley from Panel 3. By 280 million years ago, change in the configuration of the Gondwanan lands and the sea had influenced global weather patterns. Lower temperatures and expansion of the polar ice caps ensued. Gondwana was gradually covered by a wet-based continental ice sheet, which in Australia blanketed much of the southeast. This is now known as the Permian, or Gondwanan, glaciation. The flattened view might have looked something like the Antarctic ice sheet today, had there been anyone to see it (Figure 4). As it flowed, the glacier tore rock and sediment from the land surface beneath. The resulting debris, frozen into its base, gouged, scratched and polished the denuded bedrock (see Figure 9; Figure 13).
Ten million years later, during the middle Permian, the climate was warming and the ice thinned. Melt-water flowed from the surface and from under the ice depositing fine rock flour and coarser material. This accumulated in layers on the floors of melt-water lakes, as at Hallett Cove, as the glacier moved westward and north-westward. Floating icebergs, calved from the ice sheet, shed debris and rocks, or ‘dropstones’, into the sediments of the lake floor (see Figure 9).
The vocabulary of glaciers affirms John McPhee’s declaration that geology is indeed a fountain of imagery.2 Hallett Cove is no exception. Since the Permian period it has been a premier site for dropstones, erratics, lunate fractures, crescentic gouges, chatter marks, striated bedrock, roches moutonnées (named for their resemblance to recumbent sheep), lodgement till, flow till, rock flour and tenacious clay. Verbal deposits aside, the presence of these features at the cove provides evidence of the passage of a glacier and its direction. The Proterozoic rocks of Panel 1 were grooved and gouged by the ice sheet and friction marks – lunate fractures, crescentic gouges, chatter marks, striations – remained after the ice retreated. Larger rocks trapped in the glacier or in icebergs could be transported a long way, before being dumped when the ice melted. These include the glacial erratics that rest on the beach at Hallett Cove, that erode from the glacigene cliff sediments to the south, and rest on the cliff tops above (see Figure 10, Figure 12).
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Figure 9: The formation of striated pavements, glacial tills and erratics in a glacial lake. As the glacier moved west, the bedrock beneath was abraded, leaving striated pavements like Tate’s Rock. Icebergs calving into a lake at the retreating end dropped boulders and gravel as they melted, which today form part of the beach at Hallett Cove and are part of the erosion from the cliffs. (Adapted from Giesecke, 1999)
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Figure 10: Erratic boulders eroding from cliffs above Hallett Cove. (Photograph K. Douglas)
Panel 5
Above this, another unconformity marks another filled palaeovalley, a contact between the glacigene sediments and Pliocene sediments above. This contact represents another 200 million years of erosion or non-deposition. As Hallett Cove eroded during the Triassic, dinosaurs appeared. Inland Australia was covered by seas inhabited by fish and plesiosaurs. Conifers, cycads and fern prairies were common on the land. Australia and Antarctica started to separate during the Jurassic. New coastlines formed as the rifting which had begun to split Gondwana apart at the end of the Permian separated Australia and Antarctica completely by about 45 million years ago during the middle Eocene. Flowering plants, mammals and birds diversified after the decline of the dinosaurs. Many modern groups of Australian biota had appeared by the Oligocene. At the close of the Miocene, about five million years ago, the climate was warm and wet.
Panel 6
My sixth panel is set four million years ago, in the Pliocene. A warm shallow sea briefly covered low-lying land to the east of the modern Gulf St Vincent. Sediments and seashells accumulated on the sea floor, together with shellfish and the many-chambered, calcium carbonate ‘shells’ of single-celled marine organisms called foraminifera. These hardened to a fossiliferous sandstone, exposed two million years later, when the present Mount Lofty Ranges were uplifted. The sandstone is exposed in the Amphitheatre and also forms a bluff along the north-western part of the park and is the modern embodiment of this panel. The next two million years or so are again not represented by the Hallett Cove rocks. Australia became warmer and drier as its northward drift continued. Abundant rainforests were replaced by grasslands and eucalypt woodland. Grazing mammals diversified.
Panel 7
In the Pleistocene epoch, dry periods in Australia were interspersed with wet ones. During the latter, high ground eroded. As the Mount Lofty Ranges rose, sand, silt and clay washed down to the coast in streams. These thick alluvial sediments were deposited above the exposed fossiliferous sandstone. Where the land had remained above water during the Pliocene, they blanketed glacigene Permian sediments. The unconformity between is represented by Panel 5. Seasonal changes in precipitation leached calcium carbonate from the soil, which was redeposited near the ground surface in a hard layer of calcrete.
Sea level fluctuated as the Pleistocene glaciations of Europe and North America swelled and declined according to oscillations of the polar ice caps. Glacial advances correlated with sea level retreat and interglacials with marine incursions over the continental shelf. Only small areas of greater Australia – parts of Tasmania, the highlands of New Guinea and the Kosciuszko Plateau – were glaciated even at the height of the Pleistocene ice age. In fact, Pleistocene Australia could instead be said to have experienced ‘dirt ages’.
Reduced precipitation and spring run-off from the highlands made a dust bowl of the interior. Plains of ‘drift’ – formerly attributed to great floods or glaciers3 – blew across the continent, forming characteristic dune systems.4 Sea level changes sculpted the coastlines. Upstream of their drowned deltas, rivers became coastal estuaries as the sea invaded. Coastal plain became shallow sea and plain again. The inland deltas of the Riverine Plains and the Lake Eyre basin dried out. Giant marsupials browsed the forests, grazed the plains and died horribly of thirst, trapped in the mud of drying lakes. Towards the end of the Pleistocene, the ancestors of modern Aboriginal people witnessed and adapted to these changes.
Panel 8
With the retreat of the ice caps around 11 500 years ago, the sea again began to encroach on the coastal plain of Gulf St Vincent. During the Holocene it rose more than 130 metres. Kangaroo Island and Tasmania became islands once more. The Pacific Ocean flooded the Parramatta River delta to form Sydney Harbour. Waves cut cliffs into the stumps of the Delamerian Ranges, left a rocky platform at their base and removed quantities of soft glacial sediment from the beach, to expose Permian erratics at Hallett Cove. Uplift of the land surface enhanced erosion of Permian and Pliocene sediments by the creeks which washed down from the Mount Lofty Ranges and carved the badlands features of the Hallett Cove Amphitheatre. Low dunes formed on the beach. People of the Adelaide Plains occupied sunny sites along the cliffs, in the lee of the prevailing winds. These cycles of erosion, deposition and uplift continue today (see Figure 11).
The Hallett Cove Conservation Park comprises 50.48 hectares on the eastern side of Gulf St Vincent, about 20 kilometres south of the city of Adelaide, in the Hundred of Noarlunga. It is partly bounded to the south by the 3.93 hectare Sandison Reserve and partly by the low-water mark along the beach at Hallett Cove. The remainder of the park and the reserve are bordered by residential development which makes the site unusual in South Australia’s extensive system of metropolitan conservation parks. No visible boundaries separate the park from the Sandison Reserve, but a plaque marks the spot where the reserve was dedicated to the National Trust of South Australia in 1960. The trust still owns the reserve and the park is managed by the South Australian National Parks and Wildlife Service. The reserve was opened to the public in 1965 and the present boundaries of the park were dedicated a decade later. The park consists of low hills above variably rugged coastal cliffs, a grassy foreshore area near the southern boundary, an extensive rocky shore platform and sandy cove area, with deeply eroded gullies, together with westward-trending watercourses. Much of the native vegetation was cleared during the late nineteenth and early twentieth centuries and is retained in dwarfed form only in pockets of the less-accessible steep areas and in the gullies, although extensive replanting of locally indigenous flora has proceeded in recent years. Large boulders, often as big as cars, lie on the beach (see Figure 12).
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Figure 11: The Sugarloaf and Amphitheatre, Hallett Cove Conservation Park. (Photograph K. Douglas)
The area was acquired primarily to protect vulnerable geological, archaeological, botanical and historical features that would otherwise have been destroyed during urban expansion in the 1960s. These include the ‘internationally recognised’ glacial pavements and erratic boulders identified in the 1870s and ‘unique’ geology which bears ‘witness to six geological periods, each differing in climate due to Australia’s changing position on the Earth’s surface’.5 From the time of Hallett Cove’s scientific discovery in 1877, this refrain of uniqueness, international renown and significance has been regularly replayed by naturalists, scientists, journalists, residents and activists. Almost a century later an advertisement on behalf of the Save Hallett Cove Committee in September 1971 exhorted readers to ‘Save Hallett Cove’ as the ‘World famous geological treasures of this unique cove are threatened!’ Journalist Stuart Cockburn, a strong advocate for preservation of the cove’s geological wealth and a reporter with the main Adelaide newspaper, the Advertiser, explained that ‘Hallett Cove has, of course, long been known throughout Australia and overseas as a geological treasure house.’6
A field guide to Hallett Cove, published by the South Australian Museum in 1970, reiterated that the ‘unique locality, acknowledged by experts to be the best of its kind, is visited by scientists from all over the world’. The South Australian Science Teachers’ Association (SASTA) wrote in 1971 that ‘Hallett Cove is unique … Because of its Permian glacial deposits the region has worldwide significance’, restating later that ‘It is unique. It is of world renown.’ The South Australian Town and Country Planning Association described the cove as ‘one of South Australia’s most valuable resources of this type – a unique landscape unveiled by erosion to give almost unbelievable glimpses of the past’. The same authors explained in the Sunday Mail that ‘overseas geologists visit the area because of its uniqueness and international importance as a link in the theory of continental drift’ and the ‘glacial areas are quoted in many overseas texts’. The Friends of Hallett Cove, along with members of the South Australian Museum and the University of Adelaide Geology Department provided guided tours during the 1960s and 1970s, provoking such superlatives as ‘unique features’ and ‘world famous’ from reporters.7
An updated field guide to Hallett Cove, published in 1999 by the Field Geology Club of South Australia in the spirit of the museum’s 1970 edition, claimed that ‘The Cove is recognised world-wide for being one of the most important and visibly interesting records’ of the Permian ice age. In 2001 the National Trust of South Australia’s journal, Heritage Living, described the area as ‘a Mecca for geologists and naturalists since 1877’. But Ralph Tate’s last word on the matter at the fifth meeting for the Australasian Association for the Advancement of Science, held more than a century ago in Adelaide in 1893, still encapsulates the celebratory nature of South Australian geologists’ reactions to Hallett Cove: ‘Hallett’s Cove remains unique in respect of the magnitude and completeness of the glacial features which are there preserved … we may congratulate ourselves.’8
Hallett Cove’s colourful municipal history has left a residue of names, remembered events and heritage sites that invest the landscapes with local meaning beyond the essentially scientific and aesthetic significance of the conservation park. The cove itself was named for John Hallett, a prominent South Australian pastoralist and early Parliamentarian, who reportedly first saw the feature in 1837 while searching for missing stock. Hallett arrived in the new colony on the Africaine in 1836, aged 32. Land Grant records show the first sale of land to him on 14 March 1840. Alfred Hallett, his brother, joined him in 1841. John Hallett gave evidence at a court held at Kingscote, Kangaroo Island, in the late 1830s, that the cove witnessed smuggling as, to escape excise, traders put spirits and other goods ashore there and at Brighton at night by boat from Kangaroo Island, then took them north to Adelaide by bullock dray.9
Prospecting was carried out in the 1840s on behalf of investors anxious to partake of the colony’s new mineral wealth. In 1847, prospectors discovered copper ore at Worthing Farm, a property owned by the Hallett brothers, in the valley of the Field River, 800 metres south-east of Hallett Cove proper. Samples sent to London were deemed promising and the Worthing Mining Company was incorporated on 2 July 1849. The venture remained something of a family affair: ten men, including two Halletts, each contributed £1000 to purchase the land from Alfred and John, who retained a considerable vendor interest. Alfred managed the mine. The company appointed a colonial committee, which included John Hallett, and the directors in England included several other Halletts. Mining operations commenced in 1849 when Captain John Richards and a team of five working miners arrived from Cornwall to sink the first shaft. A steam engine, boiler and other machinery arrived from England late in the year and the team erected the engine early in 1850.10
During the 1850s, a community of about 100 people rapidly became dependent on the mine. The village comprised a blacksmith’s shop, ten miners’ cottages, a powder magazine, storehouse and offices and a large manager’s house, inhabited for a while by Alfred Hallett and his family. By 1855 the settlement supported a schoolmistress. The company sank three shafts half a mile apart, but the mine was never very successful. Contributing factors included low-grade ore and the hardness of the ground which made digging shafts more difficult than anticipated. The mine’s proximity to the Field River and the sea made it vulnerable to underground water, which poured in from fissures at 156 feet (48 metres), the depth of the main shaft. These agents were abetted by the exodus of miners to the lucrative Victorian goldfields in 1852 which precipitated a chronic labour shortage and inflated wages for several years. Notwithstanding its importance to the small community, the Worthing Mine closed in 1857. By 1861, the cottages were described as dilapidated and continued in increasingly derelict state until demolished over a century later. Some of the miners purchased land from the company and set up small farms. Alfred Hallett died in 1877, the year Ralph Tate announced the discovery of glacial features at Hallett Cove. The first subdivision inland of Hallett Cove was laid out in June 1913 and known as Hallett’s Cove Estate. In August 1914 another subdivision was laid out at Hallett’s Cove proper and the Hallett’s Cove Model Estate was laid out in November of that year.11 The ‘Worthing or Hallett Mine, Enginehouse and Chimney and Environs’ were nominated to the South Australian Register of State Heritage Items in September 1978 and registered on 24 July 1980, a remnant of South Australia’s industrial and geological history. The site is National Trust classified. Although the mine never contributed significantly to South Australia’s economy, its structures include the oldest surviving engine house and associated stack in Australia. It is a relic of the earliest period of base-metal mining in Australia and the most intact disused mine in metropolitan Adelaide.12
These events, trivial or momentous depending on individual or collective experience, actively shape meaning at Hallett Cove as surely as the abrasion of glaciers, the swelling of mountains, the tearing of continents and the curiosity and ambition of scientific men. And the success of the ‘Save Hallett Cove’ campaign of the 1960s and 1970s was as dependent upon the actions, experiences and dedication of communities, garage operators, mothers of four, schoolchildren and the scientifically illiterate as it was upon any meaning or value inherent in the rocks and sediments of cove landscapes as deciphered by the geological community. Experience shapes interpretation.
This is deep time and ordinary time at Hallett Cove in broad brushstrokes. But it is not just the story in the sediments or its commonplace colonial history that makes the site iconic to South Australian geologists. Hallett Cove is what the Geological Society of Australia terms a classical site – a canonical location associated with the development and articulation of geological concepts – in this case, nineteenth-century glacial studies in Australia.
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