NUMBER 80 | JUNE 2015

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In this issue...• ‘Small, individually nondescript and

easily overlooked’: Contact beads from northwest Arnhem Land in an Indigenous-Macassan-European hybrid economy | Daryl Wesley and Mirani Litster

• The palaeo-environmental history of Big Willum Swamp, Weipa: An environmental context for the archaeological record | Janelle Stevenson, Sally Brockwell, Cassandra Rowe, Ulrike Proske and Justin Shiner

• A multidisciplinary investigation of a rock coating at Ngaut Ngaut (Devon Downs), South Australia | Amy Roberts, Isobelle Campbell, Allan Pring, Graham Bell, Alan Watchman, Rachel S. Popelka-Filcoff, Claire E. Lenehan, Christopher T. Gibson, Natalie Franklin and the Mannum Aboriginal Community Association Inc. (MACAI)

• Thy Thylacoleo is a thylacine | David M. Welch

• A fine-grained analysis of the macropod motif in the rock art of the Sydney region, Australia | Alandra K. Tasire and Iain Davidson

• Investigating standardisation in the form of backed artefacts at two sites in the Hunter River valley, NSW, Australia | Marika A. Low

• Mapping a millstone: The dynamics of use-wear and residues on a Central Australian seed-grinding implement | Mike Smith, Elspeth Hayes and Birgitta Stephenson

• Compliance-based archaeological heritage management and place-based participatory mapping for negotiated outcomes | David R. Guilfoyle and Myles B. Mitchell

• Attributes, preservation and management of dendroglyphs from the Wet Tropics rainforest of northeast Australia | Alice Buhrich, Åsa Ferrier and Gordon Grimwade

• Mid-Holocene exploitation of marine molluscs in the lower Mid West, Western Australia | Carly Monks, Bob Sheppard and Joe Dortch

• The archaeology of Bindjarran rockshelter in Manilikarr Country, Kakadu National Park, Northern Territory | Denis Shine, Melissa Marshall, Duncan Wright, Tim Denham, Peter Hiscock, Geraldine Jacobsen and Sean-Paul Stephens

• The Brremangurey pearl: A 2000 year old archaeological find from the coastal Kimberley, Western Australia | Katherine Szabo, Brent Koppel, Mark W. Moore, Iain Young, Matthew Tighe and Michael J. Morwood

Position Name Address

Executive

President Fiona HookArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Vice PresidentPeter Veth Archaeology, Social Sciences, The University of Western Australia,

35 Stirling Highway, Crawley WA 6009Jo McDonald

Secretary Martin PorrArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Treasurer Benjamin SmithArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Assistant Treasurer Sven OuzmanArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Membership Secretaries

Tom WhitleyArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Leslie Zubieta

Jamie Hampson

Public Officer Sally BrockwellArchaeology and Natural History, School of Culture, History and Language, College of Asia and the Pacific, The Australian National University, Canberra ACT 0200

Webmaster Sam HarperArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Indigenous Liaison Officers

Christopher WilsonYunggorendi First Nations Centre for Higher Education and Research, Flinders University, GPO Box 2100, Adelaide SA 5001

Kellie Pollard Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001

Media Liaison Officer Elspeth Hayes Centre for Archaeological Science, University of Wollongong, Wollongong NSW 2533

Student Representatives

Georgia Roberts Archaeology Program, La Trobe University, Bundoora Vic. 3086

Lucia Clayton-Martinez

Archaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Australian Archaeology Editorial Committee

EditorsHeather Burke Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001

Lynley Wallis Wallis Heritage Consulting, 1B Swan St, Brighton SA 5048

Editorial Assistant Susan Arthure Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001

Short Report Editor Sean WinterArchaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009

Book Review EditorsClaire St George Ochre Imprints, 6/7 Mayfield Street, Abbotsford Vic. 3067

Alice Gorman Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001

Thesis Abstract Editor Tiina Manne School of Social Science, The University of Queensland, St Lucia Qld 4072

Commissioned Bloggers

Jacqueline Matthews Archaeology, Social Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009Carly Monks

Michelle LangleySchool of Archaeology and Natural History, College of Asia and the Pacific, The Australian National University, Canberra ACT 0200

Jordan Ralph Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001

State Representatives

Australian Capital Territory

Michelle LangleySchool of Archaeology and Natural History, College of Asia and the Pacific, The Australian National University, Canberra ACT 0200

New South Wales Alan WilliamsArchaeological and Heritage Management Solutions, 349 Annandale Street, Annandale NSW 2038

Northern Territory Malcolm Connolly PO Box 843, Alice Springs NT 0871

Queensland Dee Gorring School of Social Science, The University of Queensland, St Lucia Qld 4072

South Australia Belinda Liebelt B G L Heritage Consulting, 3 Sheringa Avenue, Ingle Farm SA 5098

Tasmania Anne McConnell GPO Box 234, Hobart Tas. 7001

Victoria John Tunn Archaeological and Heritage Management Solutions, 2/35 Hope Street, Vic. 3056

Western AustraliaJane Skippington Archaeology, Social Sciences, The University of Western Australia,

35 Stirling Highway, Crawley WA 6009Cheng Yen Loo

Australian Archaeology, the official publication of the Australian Archaeological Association Inc., is a refereed journal published since 1974. It accepts original articles in all fields of archaeology and other subjects relevant to archaeological research and practice in Australia and nearby areas. Contributions are accepted in eight sections: Articles (5000–8000 words), Short Reports (1000–3000), Obituaries (500–2000), Thesis Abstracts (200–500), Book Reviews (500–2000), Forum (5000), Comment (1000) and Backfill (which includes letters, conference details, announcements and other material of interest to members). Australian Archaeology is published twice a year, in June and December. Notes to Contributors are available at: <www.australianarchaeologicalassociation.com.au>.

Australian Archaeology is indexed in the Arts and Humanities, Social and Behavioural Sciences, and Social Sciences Citation Indices of the Thomson Reuters Web of Knowledge, SCOPUS, Australian Public Affairs Information Service (APAIS), and Anthropological Literature and Anthropological Index Online.

Australian Archaeology is ranked as a tier A journal by the European Reference Index for the Humanities and French Agence d’Evaluation de la Recherche et de l’Enseignement Supérieur.

Subscriptions are available to individuals through membership of the Australian Archaeological Association Inc. or to organisations through institutional subscription. Subscription application/renewal forms are available at <www.australianarchaeologicalassociation.com.au>. Australian Archaeology is available through Informit and JSTOR.

Design and Print: Openbook Howden

Front Cover: Studying a Nautilus shell during midden sorting (Annette Oertle, entered in the AAA 2014 Photography Competition).

All correspondence and submissions should be addressed to:

Australian Archaeology

PO Box 10, Flinders University LPO

Flinders University SA 5048

Email: journal@australianarchaeology.com

<http://www.australianarchaeologicalassociation.com.au>

The views expressed in this journal are not necessarily those of the Australian Archaeological Association Inc. or the Editors.

© Australian Archaeological Association Inc., 2015

ISSN 0312-2417

Editors

Heather Burke Flinders UniversityLynley Wallis Wallis Heritage Consulting

Editorial Advisory Board

Brit Asmussen Queensland MuseumHuw Barton Leicester UniversityNoelene Cole James Cook UniversityPenny Crook La Trobe UniversityInes Domingo Sanz University of BarcelonaJudith Field University of New South WalesJoe Flatman University College LondonRichard Fullagar University of WollongongTracy Ireland University of CanberraMarlize Lombard University of JohannesburgAlex Mackay University of Wollongong Scott L’Oste-Brown Central Queensland Cultural Heritage ManagementJo McDonald The University of Western AustraliaPatrick Moss The University of QueenslandTim Murray La Trobe UniversityJim O’Connell University of UtahSven Ouzman The University of Western AustraliaFiona Petchey University of WaikatoAmy Roberts Flinders UniversityKatherine Szabo University of WollongongNancy Tayles University of OtagoRobin Torrence Australian MuseumPeter Veth The University of Western AustraliaAlan Watchman Flinders UniversityDavid Whitley ASM Affiliates Inc.Nathan Woolford Nathan Woolford Consultants

Short Report Editor

Sean Winter The University of Western Australia

Book Review Editors

Alice Gorman Flinders UniversityClaire St George Ochre Imprints

Thesis Abstract Editor

Tiina Manne The University of Queensland

Editorial Assistant

Susan Arthure Flinders University

Commissioned Bloggers

Jacqueline Matthews The University of Western AustraliaCarly Monks The University of Western AustraliaMichelle Langley The Australian National UniversityJordan Ralph Flinders University

Australian Archaeological Association Inc.Office Bearers for 2015

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June 2015, Volume 80

Editorial | Heather Burke and Lynley A. Wallis iii

Articles

‘Small, individually nondescript and easily overlooked’: Contact beads from northwest Arnhem Land in an Indigenous-Macassan-European hybrid economy | Daryl Wesley and Mirani Litster 1

The palaeo-environmental history of Big Willum Swamp, Weipa: An environmental context for the archaeological record | Janelle Stevenson, Sally Brockwell, Cassandra Rowe, Ulrike Proske and Justin Shiner 17

A multidisciplinary investigation of a rock coating at Ngaut Ngaut (Devon Downs), South Australia | Amy Roberts, Isobelle Campbell, Allan Pring, Graham Bell, Alan Watchman, Rachel S. Popelka-Filcoff, Claire E. Lenehan, Christopher T. Gibson, Natalie Franklin and the Mannum Aboriginal Community Association Inc. (MACAI) 32

Thy Thylacoleo is a thylacine | David M. Welch 40

A fine-grained analysis of the macropod motif in the rock art of the Sydney region, Australia | Alandra K. Tasire and Iain Davidson 48

Investigating standardisation in the form of backed artefacts at two sites in the Hunter River valley, NSW, Australia | Marika A. Low 60

Mapping a millstone: The dynamics of use-wear and residues on a Central Australian seed-grinding implement | Mike Smith, Elspeth Hayes and Birgitta Stephenson 70

Compliance-based archaeological heritage management and place-based participatory mapping for negotiated outcomes | David R. Guilfoyle and Myles B. Mitchell 80

Attributes, preservation and management of dendroglyphs from the Wet Tropics rainforest of northeast Australia | Alice Buhrich, Åsa Ferrier and Gordon Grimwade 91

Short Reports

Mid-Holocene exploitation of marine molluscs in the lower Mid West, Western Australia | Carly Monks, Bob Sheppard and Joe Dortch 99

The archaeology of Bindjarran rockshelter in Manilikarr Country, Kakadu National Park, Northern Territory | Denis Shine, Melissa Marshall, Duncan Wright, Tim Denham, Peter Hiscock, Geraldine Jacobsen and Sean-Paul Stephens 104

The Brremangurey pearl: A 2000 year old archaeological find from the coastal Kimberley, Western Australia | Katherine Szabo, Brent Koppel, Mark W. Moore, Iain Young, Matthew Tighe and Michael J. Morwood 112

Backfill

Obituary: James Semple Kerr (1932–2014) | Richard Mackay, AM 116

Thesis Abstracts - Available online

Rich Pickings: Abandoned Vessel Material Reuse on Rangitoto Island, New Zealand | Kurt Bennett

The Law of the Sea: How Ratifying the UNESCO Convention Will Affect Underwater Cultural Heritage Management in Australia | Thomas Body

Undressing the Past: A Study of the Correlation between Waistcoat Design and Broad Sociocultural Trends of Nineteenth and Early Twentieth Century Australia | Jessica Megan Boman

Socioeconomic Status in Nineteenth Century Diet at The Rocks, Sydney, Australia: The Effects of Government Regulation and Institutionalisation | Annabelle Brealey

Table of Contents

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‘Inland’ Versus ‘Coastal’: An Analysis of Archaeological Shell Remains to Determine Habitat Exploitation Patterns at Edubu 2, South Coast of Papua New Guinea | Anna Garamszegi

Who Were the People of Ancient Vilabouly? Exploring Origins and Relationships through the Study of Ge | Catherine Livingston

Understanding Australia’s Cultural History through Archaeological Geophysics | Kelsey M. Lowe

Communicating Cultural Complexity: The Interpretation of a Physically Impacted Aboriginal Shell Midden at Point Lookout, North Stradbroke Island, Queensland | Anna Nelson

What You Lookin’ At?: An Archaeological Analysis of Graffiti and Inscription at Fremantle Prison, Western Australia | B’geella Romano

A Woman’s Place … : An Historical Archaeological Investigation of Identity and Power on the Nineteenth Century Pastoral Landscape of Southeast Queensland | Linda Terry

Understanding a Contested Heritage Place | Anna Weisse

Assessing Mid- to Late Holocene Predation of Conomurex luhuanus and Tectus niloticus at Lizard Island, Northeastern Australia | Samantha Aird

An Archaeobotanical Analysis of Macrobotanical Remains at Riwi Cave in the South-Central Kimberley Region, WA | India Ella Dilkes-Hall

The Economic Impact of Convict Transportation on the WA Economy 1850–1900: An Archaeological Investigation | Alyce Haast

An Analysis of the Risk Hypothesis and its Application to Hunter-Gatherer Toolkits Using an Australian Dataset | Emma Rehn

Cultural Competition: A Darwinian View of Cultural Evolution as it Applies to the Early Development and Interaction Between Rome and Etruria | Matilda Vanessa Stevens

Disembodied and Displaced: An Archaeological Enquiry into the Historical Colonial South Trade of Indigenous Human Remains and Artefacts, and the Contemporary Repatriation and Rehumanisation of Indigenous Australians from South Africa | Tahlia Stewart

Book Reviews - Available online

First Footprints: The Epic Story of the First Australians by Scott Cane | Douglas Bird

Historical Archaeologies of Cognition: Explorations into Faith, Hope and Charity edited by James Symonds, Anna Badcock and Jeff Oliver | Edwina Kay

The Science of Human Origins by Claudio Tuniz, Giorgio Manzi and David Caramelli | Iain Davidson

Australia’s Fossil Heritage: A Catalogue of Important Australian Fossil Sites by the Australian Heritage Council | Judith Field

Art and Archaeology: Collaborations, Conversations, Criticisms edited by Ian Alden Russell and Andrew Cochrane | June Ross

A Companion to Rock Art edited by Jo McDonald and Peter Veth | Ken Mulvaney

Working With Rock Art: Recording, Presenting and Understanding Rock Art Using Indigenous Knowledge edited by Benjamin Smith, Knut Helskog and David Morris | Sven Ouzman

The Death of Prehistory edited by Peter Schmidt and Stephen Mrozowski | John Giblin

Archaeological Dimensions of World Heritage: From Prevention to Social Implications edited by Alicia Castillo | Ian Lilley

An Archaeology of Institutional Confinement. The Hyde Park Barracks, 1848–1886 by Peter Davies, Penny Crook and Tim Murray | Susan Piddock104

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A multidisciplinary investigation of a rock coating at Ngaut Ngaut (Devon Downs), South AustraliaAmy Roberts1, Isobelle Campbell2, Allan Pring3,5, Graham Bell4, Alan Watchman1, Rachel S. Popelka-Filcoff 5, Claire E. Lenehan5, Christopher T. Gibson6, Natalie Franklin1, 7 and the Mannum Aboriginal Community Association Inc. (MACAI)1. Department of Archaeology, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia <amy.roberts@flinders.edu.au>2. Mannum Aboriginal Community Association Inc., Nildottie SA 5238, Australia3. South Australian Museum, North Terrace, Adelaide SA 5000, Australia <Allan.Pring@samuseum.sa.gov.au>4. Department of Environment, Water and Natural Resources, State Herbarium, North Terrace, Adelaide SA 5000, Australia

<Graham.Bell@sa.gov.au>5. School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia

<rachel.popelkafilcoff@flinders.edu.au> <allan.pring@flinders.edu.au> <claire.lenehan@flinders.edu.au>6. Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100,

Adelaide SA 5001, Australia <christopher.gibson@flinders.edu.au>7. School of Social Science, The University of Queensland, St Lucia Qld 4072, Australia <n.franklin@uq.edu.au>

Abstract

This paper presents the results of a multidisciplinary investigation into a dark rock coating at the Ngaut Ngaut heritage complex in South Australia (SA) using geological and botanical examination, Raman microscopy, x-ray powder diffraction, scanning electron microscopy and infrared analyses. The coating analysed contains a mixture of calcite, quartz, gypsum and weddellite. The presence of calcite and quartz can be explained by the underlying clastic fossiliferous limestone, while the most probable explanation for the origin of the gypsum is via ground water. The weddellite was likely formed from solutions derived from the reaction of calcite with oxalic acid through the intervention of surface microflora, such as algae. This article provides the first record of weddellite in any context in SA. These findings have a number of implications—one being that the oxalate mineral in the rock coating could potentially be used to conduct accelerator mass spectrometry radiocarbon analysis and thereby refine our understanding of the rock art chronology at Ngaut Ngaut. A greater understanding of the rates of accumulation may also be useful for management purposes, as the nature of the rock coating may be contributing to long-term exfoliation. Indeed, it is argued that algal colonisation of the limestone (together with other probable microfloral activities) is likely involved in the production of a film over the porous surface, leading to salt weathering.

Introduction

Ngaut Ngaut (formerly Devon Downs) is primarily known in the archaeological literature as the first stratified rockshelter deposit to be scientifically excavated in Australia (e.g. Horton 1991:153; Mulvaney and Kamminga 1999:11). Prior to Hale and Tindale’s (1930) work at this site little systematic research had been conducted in the field of Australian archaeology. In fact, the thinking of the day was that Indigenous Australians were recent arrivals to Australia and that their material culture had not changed through time (Mulvaney and Kamminga 1999:12). Thus, the research at Ngaut Ngaut was a turning point in the way that the Australian archaeological record and Indigenous history were viewed by non-Indigenous people (Roberts and MACAI 2012). The Aboriginal community,

however, would like this significant heritage complex also to be acknowledged for the range of other important cultural values that are attached to it (e.g. Roberts and Campbell 2012; Roberts and MACAI 2012).

Investigations into a thin, dark rock coating on the rockshelter ceiling and adjacent surfaces at Ngaut Ngaut began with the realisation that a significant section of petroglyphs engraved into this coating had sheared off the limestone surface at some time post-1929 (Roberts et al. 2014). The rock art typology/chronology put forward by Hale and Tindale (1930), as well as syntheses published by subsequent researchers, has recently been reconsidered (Roberts et al. 2014) and a detailed discussion of these issues is not reiterated here. However, in general terms Roberts et

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al. (2014) concluded that there were some issues with Hale and Tindale’s (1930) typology (e.g. in relation to their ‘Type A’ abraded grooves), and agreed that the figurative motifs were likely to predate the non-figurative motifs (at least in the western section of the rockshelter). The figurative and non-figurative motifs are arguably less than 3000 years old based on the associated dating of rock falls at the site, whilst the occupation of the rockshelter began more than 5000 years ago (Roberts and MACAI 2012:19–20).

Background

Location and Geological Setting

Ngaut Ngaut is located between the towns of Nildottie and Mannum on the Murray River in South Australia (SA) (Figure 1). The rockshelter, which forms part of a larger heritage complex, is one of several located within the gorge that are significant to traditional owners. The primary occupation area at Ngaut Ngaut occurs close to the river, where the cliff is fronted by a short debris slope and above the usual high river flows. Several floods have been recorded in historical times, the highest being in 1956, when the Murray River rose some 6–7 m above average river level. Remnants of a deposit of angular and ill-sorted quartz sand, corresponding to the height of the river at that time, are plastered on strata exposed in the 1929 excavation and adjacent cliff faces. A flood of roughly equal height occurred about 3000 years ago and is recorded in the strata exposed in an excavation at nearby Tungawa (Fromms Landing) in 1961 (Lawton et al. 1963; Mulvaney et al. 1964; Twidale 1964).

In its lower reaches the River Murray flows in a gorge some 20–50 m deep and between 750 m and 1.5 km wide, extending between Overland Corner (approximately 35 km east of Waikerie) and the vicinity of Wellington (approximately 60 km south of Mannum) (Twidale and Bourne 2009). In forming the gorge, the river has cut through the Mannum Limestone, of marine origin and Miocene age (ca 20 million years old), to form the orange-brown cliffs for which the feature is well known. The river first eroded a relatively shallow and

wide valley in the riverine Loxton Sand and Mannum Limestone some 3–4 million years ago. A rise in sea level caused it to be inundated and become an estuary in which the sand and oyster beds of the Norwest Bend Formation were deposited.

The succeeding Pleistocene period saw the fall and rise of sea levels. The present gorge was excavated by the Murray at times of low sea level, when the river extended far to the south to the edge of the continental shelf, and deep canyons were eroded in the continental slope. The gorge then was deeper than it is now, for the rise in sea level following the most recent glaciation caused the river to deposit up to 20 m of alluvium.

The river winds across the broad floor of the gorge, forming a series of loops or meanders. Where the outside of the loops impinge on the valley sides, a steep cliff occupies the whole of the slope, while on the inside there are gentle debris or slip-off slopes and lagoons. The pattern of meanders moves downstream as a result of the undermining of cliffs and the concomitant deposition of debris on the inside curve of the channel. Thus, and as noted by Sturt (1833) and Tate (1884), there are alternations of slope form in the walls of the gorge. Even though there are a series of locks controlling the river’s flow, it experiences periods of higher and lower flow, as well as occasional floods.

Ngaut Ngaut Petroglyphs

Petroglyphs at Ngaut Ngaut and on adjacent cliff faces are engraved into the Mannum Limestone and, as noted above, comprise both figurative (including ‘tortoise’ and ‘sun’ motifs) and non-figurative motifs (including lines, dots and tracks) (see Roberts et al. 2014 for more detail). Some of the Ngaut Ngaut motifs are engraved through the dark rock coating, whilst others are infilled or partially infilled with it (Figures 2 and 3); yet others are engraved into surfaces that have no coating. Such observations reveal the potential for the coating to be used to refine the dating of the petroglyphs.

The condition of the petroglyphs became a cause for concern subsequent to observations made in 2012. As can be noted in the before (Figure 4) and after (Figure 5) images, it appears that the rock coating area that contained Tindale’s Type B motifs in the top left of the photograph has sheared off the limestone surface (a close-up photograph of the motifs in this area was also taken by Sheard [1927:Plate IV, Fig. 1]); however, the petroglyphs at the right of the image appear similar in preservation to the 1929 recordings.

This discovery led to questions about the composition of the rock coating, whether it provided any datable material and management issues. Previous commentary on the rock coating has largely argued that it is a ‘thick carbonaceous deposit resulting from fires lit in the shelter’ (Hale and Tindale 1930:210; see also Sheard 1927:18). Hale and Tindale (1930:210) also contended that the ‘deposit’ served to protect the petroglyphs from ‘atmospheric weathering’. Other researchers have also drawn correlations between the blackened cliff face and habitation by Aboriginal people (Lawton et al. 1963; Mulvaney et al. 1964), as do community understandings and oral histories. Research conducted by Roberts (1998:19) in collaboration with MACAI in relation to the engravings at nearby Tungawa (Fromms Landing), postulated that a similar (although more developed) rock coating appeared also to contain lichen growth that seemed to be filling in drilled holes at Shelter 3 (Figure 6) (see Maynard [1997:291] and Roberts et al. [2014:40] for further information on the drilling technique as used in this region).

Figure 1 Location of Ngaut Ngaut and other well-known archaeological sites (including Tungawa [Fromms Landing], Tartanga and Roonka), as well as major townships and additional places of Aboriginal significance in the region. The grey line indicates the Murray River. Map adapted from Roberts and MACAI (2012).

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Given these questions, and particularly due to the fact that there were potential management issues, MACAI approved follow-up research to investigate the rock coating. It was decided early on that a multidisciplinary approach would be employed, with specialists engaged who used the following methods to analyse the rock coating: geological and botanical examination; Raman microscopy (a technique used to provide mineralogical analysis by measuring the wavelength and intensity of inelastically scattered light from molecules, e.g. Colthup et al. 1990); x-ray powder diffraction (used to provide mineralogical analysis via ‘a rapid analytical technique primarily used for phase identification of a crystalline material’ and which can ‘provide information

on unit cell dimensions’ [Dutrow and Clark 2013]); scanning electron microscopy; and infrared analyses (conducted to investigate the infrared region of the electromagnetic spectrum, e.g. Colthup et al. 1990). These methods are further detailed below.

Methods

Geological and Botanical Examination

The rock coating at Ngaut Ngaut was visually examined with the aid of x10 magnification on 11 July 2013. It was determined that no immediate geological explanation could be given for its formation and, as with Roberts’ (1998) assessment of the Tungawa rock coating, it was speculated that the coating may be, at least partly, the result of microfloral activities. Approval for sampling had been pre-arranged with MACAI and two small samples were taken under the direction of MACAI representatives from the eastern end of the Ngaut Ngaut cliff face where there were no engravings present (Samples 1 and 2 [Figure 7 shows an example]). These samples were taken from locations where the rock coating was clearly in the process of shearing away from the limestone surface. Both samples were then subjected to a more detailed examination under x400 magnification.

Raman Microscopy

Raman microscopy was the first mineralogical analysis to be trialled on both the blackened particles and the light brown particles from the underlying Mannum Limestone

Figure 2 An example of a ‘tortoise’ motif at Ngaut Ngaut engraved into the dark rock coating covering the Mannum Limestone (photograph by Tegan Burton).

Figure 3 Example of drilled holes partly infilled with dark rock coating at Ngaut Ngaut (photograph by Tegan Burton).

Figures 4 and 5 The left image (4) is a photograph of the art panel at the western end of Ngaut Ngaut rockshelter in 1929. The dotted line indicates a rock fall line according to Hale and Tindale (1930) (image courtesy of the South Australian Museum Archives, AA338/50/26, Tindale Collection). The right image (5) is a photograph of the same panel in 2012 (photograph by Isabel Wheeler). Note the missing petroglyphs in the top left of the image in comparison to the 1929 photograph.

Figure 6 Drilled holes with partial rock coating infill at Tungawa (Fromms Landing) (photograph by Amy Roberts).

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from Sample 1. A small amount of each group of the coloured particles (<1 mg) was placed on a standard microscope slide and examined with a Witec Alpha 300RS confocal Raman microscope. A 40x objective (Numerical Aperture 0.6) was used, with an approximate laser spot size of 1 µm. Raman data collected by the WiTEC Control software with the surface perpendicular to the excitation source. Excitation wavelengths of 532, 633 and 785 nm were used to analyse the blackened particle samples. The maximum laser power possible for each wavelength is approximately 30, 10 and 70 mW, respectively, although it should be noted that the effective power levels used to collect Raman spectra were a fraction of the maximum laser power levels. Approximately 20–30 single spectra were collected on the sample surface per laser excitation wavelength. Typical integration times for the single spectra were approximately 10–30 seconds, with 3–30 accumulations.

Powder X-Ray Diffraction

Room-temperature powder x-ray diffraction (XRD) patterns of Sample 1 were collected using a Huber Guinier Image Plate G670 with CoKα

1 radiation (λ = 1.78892 Å). The specimens

were ground under acetone in an agate mortar and spread on mylar film. Powder diffraction data was collected for 30 minutes and the mineralogy determined using powder diffraction files standard patterns.

Scanning Electron Microscopy

Subsequent to the collection of XRD patterns of Sample 1, initial attempts were made to obtain scanning electron microscope (SEM) images from the same sample; however, the sample dehydrated in the vacuum. A subsequent attempt using a FEI Quanta 450 High Resolution Field Emission Environmental SEM at Adelaide Microscopy, University of Adelaide, fitted with an energy dispersive x-ray spectrometer, was used for semiquantitative chemical analysis and characterisation of the morphological and textural features of Sample 1 grains. Several millimetre-sized fragments of the black coating from Sample 1 were mounted on a standard SEM stub using a conductive carbon tape. The sample was analysed and imaged in low vacuum mode to prevent dehydration.

Infrared Analyses

Infrared (IR) analyses were also conducted on Sample 1. Samples were prepared by grinding <1 mg with approximately 200 mg of potassium bromide in a mortar and pestle. The resultant mixture was transferred to a hydraulic dye press and a pressure of 10 ton applied for 5 minutes whilst under vacuum. The resulting disc was presented to the IR spectrometer. IR spectra were recorded using a Perkin Elmer Frontier FTIR Spectrometer. Mid-infrared spectra were acquired over the range 4000–650 cm-1 using a resolution of 4 cm-1 and a scan speed of 0.2 cm-1s-1, with 100 scans per spectrum.

Results

Botanical Examination

No biological material was observed in Sample 1; however, microscopic material was observed within the rock coating layer of Sample 2. The material consisted of a variety of unicellular organisms with a cell size of <2.5 µm, apparently including cyanobacteria (‘blue-green algae’) and probably a suite of other bacterial forms. Further identification of the observed micro-organisms is not possible at present, as little research has been carried out at this level on soil cyanobacteria in Australia, and there are currently no known experts in this field. It must also be noted that few general conclusions can be drawn from the single sample available. It can readily be observed that the crust is more highly developed at the Tungawa site (Figure 6), where it may also contain lichens. It is therefore most likely, from first principles and from international literature comparisons, that the precise composition of the soil crust microflora could vary substantially from site to site; as such, more research in this area is warranted.

Raman Microscopy

The Raman analysis of the blackened particles from Sample 1 did not produce any diagnostic peaks due to fluorescence at each of the laser wavelengths; however, approximately 30 single spectra with obvious peaks were obtained on the light brown particles from the same sample with the 785 nm laser, which matched the Raman spectra for calcite (see Wopenka et al. 2002). This was expected given the known underlying geology. The integration times for single spectra were between 2–20 seconds, with 2–3 accumulations. Figure 8 shows a typical example of Raman spectra on the light brown particles from Sample 1. The data is unprocessed and shows not only the diagnostic Raman peaks for calcite, but also the typical background fluorescence present on all Raman spectra collected.

Powder XRD

As the Raman analysis of the blackened particles from Sample 1 did not produce any diagnostic peaks due to fluorescence, it was necessary to proceed with a powder XRD study. The powder XRD study of Sample 1 revealed that the rock coating consisted of a mixture of quartz (SiO

2),

calcite (CaCO3) gypsum (CaSO

4.2H

2O) and the rare oxalate

mineral weddellite (Ca(C2O

4).2H

2O) (see Figure 9). This

deposit is the first recorded occurrence of weddellite in SA, although the mineral has been reported in caves from the Western Australian side of the Nullarbor Plain (Anthony et al. 2003).

Figure 7 Close-up of one of the samples taken for study (Sample 1, fragment measures 3 x 2 cm) (photograph by Amy Roberts).

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SEM

As the powder XRD study revealed the presence of weddellite, SEM was utilised to determine the form of weddellite present in Sample 1. Some weddellite occurred as corroded tabular to prismatic crystals up to 5 µm in length, sometimes as small clusters of crystals, but more generally

are botryoidal crusts—this is the type that may be observed in the Ngaut Ngaut rock coating (see Figures 10 and 11).

Infrared Analyses

The IR results were consistent with the rock coating being predominantly calcium oxalate (see Figure 12). However, as has been previously noted (see Echigo et al. 2005), calcium oxalate minerals are not very distinctive in their IR patterns, with whewellite, caoxite and weddellite all exhibiting very similar spectra. As such, this analysis, whilst not confirming the XRD results specifically, can be considered to be in keeping with the finding that the rock coating contains weddellite.

Discussion

Microscopic analysis indicates the presence of minute unicellular types, probably including cyanobacteria, in the rock coating in at least one sample from Ngaut Ngaut. This supports other studies (e.g. Del Monte and Sabbioni 1987; Del Monte et al. 1987; Lazzarini and Salvadori 1989; Pinna 1993; Wadsten and Moberg 1985) relating to the biodeteriogens acting on stone monuments, where the blackening of limestone building materials has been attributed to algal growths (see also Miller et al. 2011; Smith and McGreevy

Figure 8 Raman peaks obtained on the light brown particles from Sample 1 with the 785 nm laser. The peaks match the Raman spectra for calcite (see Wopenka et al. 2002).

Figure 9 XRD trace showing peaks of the rock coating from Ngaut Ngaut Sample 1. The main peaks of the principal minerals are labelled.

Figures 10 and 11 SEM images of the rock coating from Ngaut Ngaut Sample 1 showing botryoidal crusts of weddellite and gypsum with tabular to prismatic crystals of weddellite.

Figure 12 FT IR spectra of Ngaut Ngaut Sample 1 overlaid with a reference calcium oxalate specimen.

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2013; Tomaselli et al. 2000). This finding is of concern in relation to the rock art in the mid-Murray region, as algal colonisation of limestone can be associated with a ‘pitting of the surface’ (by exogenetic algae) and can contribute to the ‘disaggregation of the stone from within’ (by endogenetic algae) (Smith and McGreevy 2013). In addition, any impermeable layer deposited as a film over a porous surface will inhibit the ability of the stone to ‘breathe’, so that dissolved salts will crystallise behind the coating, leading to ‘salt weathering’ (Smith and McGreevy 2013). Consequences of this process include granular disintegration and sheet spalling. It would seem that the latter process is at play at Ngaut Ngaut, with the ultimate effect resulting in a continual expansion and contraction of the surface, leading to physical breakdown.

The discovery through XRD analysis that the rock coating contained a mixture of calcite, quartz, gypsum and weddellite was both an expected and unexpected result. The presence of calcite and quartz was expected given that the underlying geology is clastic limestone and the most probable origin of gypsum can be explained as resulting from groundwater. However, the presence of the oxalate mineral weddellite was surprising, as this mineral has not previously been recorded in SA.

Weddellite, a dihydrate calcium oxalate salt, is commonly associated with whewellite, a monohydrated calcium oxalate (see below). Weddellite is a major component of oxalate type urinary calculi in mammals (e.g. Tazzoli and Domeneghetti 1980). It can be formed from bat guano (Frost 2004; Ralph and Chau 2014; Snow et al. in press), occurs in some soils/sediments (e.g. Graustein et al. 1977) and can be formed by the reaction of calcite with oxalic acids derived from microorganisms, such as lichens, fungi and algae (e.g. Beazley et al. 2002; Pinna 1993; Russ et al. 1995). If the oxalate anion comes into solution with even low calcium concentrations then it will be precipitated as either the mono or the dihydrate salt. The phase that forms depends on whether the Ca+2 ion or the oxalate-2 ion is in excess (Frey-Wyssling 1981). Diffusion of Ca+2 into an oxalate environment forms the monohydrate (whewellite), while C

2O

42- diffusing into a calcium-rich environment forms

the dihydrate (weddellite). Given this, we argue that the weddellite formation at Ngaut Ngaut occurred when oxalic acid secreted by micro-organisms reacted with the calcite on the surface of the limestone to precipitate calcium oxalate before the oxalate could be broken down further by enzymes. Whewellite (Ca(C

2O

4)H

2O) is a thermodynamically

stable form and any weddellite formed will transform in time to whewellite if it remains in the presence of water, since it needs to recrystallise to transform from the dihydrate to the monohydrate (Snow et al. 2014). Given that the latter process has not occurred at Ngaut Ngaut, this indicates that the rockshelter has been dry for the vast majority of the time since the weddellite was deposited.

Whilst bat (and bird) guano has been observed by the authors at Ngaut Ngaut, we do not attribute it as the most likely source of the weddellite. Guano is usually high in phosphorus, nitrogen and potassium, and consists of ammonium oxalate, urate and phosphates, none of which were detected in the Ngaut Ngaut samples. The weddellite in the dark coating thus derives from a micro-organic source and the carbon contained in the mineral structure is undoubtedly from the contemporary environment and therefore may be suitable for radiocarbon analysis (see Beazley et al. 2002).

Mineralised skins or rock surface accretions at rock art sites that include carbon-bearing oxalate salts, such as whewellite and weddellite, may be removed in layers and subjected to AMS radiocarbon analysis (Cole and Watchman 2005; Mazel and Watchman 2003; Smith et al. 2009; Watchman 2001; Watchman et al. 2000, 2004). The latter investigations have demonstrated that the systematic removal of the dark coating in a micro-excavation will generate a series of microstratigraphic powders containing the datable oxalate mineral and therefore can be used to determine when the coating started forming over an engraving, providing a minimum limiting age for the petroglyph. Thus, sampling of the coating above and around rock engravings at Ngaut Ngaut (and potentially elsewhere in the mid-Murray), and subsequent AMS analysis, has the potential to refine rock art age estimates, particularly given that some motifs have been engraved through the rock coating and others are infilled with it. Such an analysis may also enable an understanding of rates of rock coating formation that can be linked to management issues. More research, including the production of cross-sections of the rock coating, would also be valuable in this regard.

As argued above, some weddellite occurs as corroded tabular to prismatic crystals up to 5 µm in length, sometimes as small clusters of crystals, but more generally as botryoidal crusts—this is the type present at Ngaut Ngaut. No formations resembling flakes of soot were identified in the SEM analysis of Sample 1, which was examined down to <2 microns. The brown-black color of the rock coating, in this sample at least, is therefore due to inclusions of organic carbon, probably from the decomposition of the microflora. Whilst this finding is not in keeping with Hale and Tindale’s (1930:210) hypothesis—i.e. that the rock coating was a ‘thick carbonaceous deposit resulting from fires lit in the shelter’ (see also the observations of Sheard [1927:18]) and more particularly due to community understandings (via oral histories) that the deposit relates to occupation—we recommend further testing of additional samples to examine this issue in more detail.

Conclusions

Given the analyses outlined above, it can be argued that the Ngaut Ngaut rock coating samples analysed in this research (and, by extrapolation, possibly other rock art sites in the mid-Murray, such as Tungawa) contain a mixture of calcite, quartz, gypsum and weddellite. The presence of calcite and quartz can be explained given the underlying geology, whereas gypsum crystallisation has probably resulted from ground water. Weddellite was likely formed from solutions derived from the reaction of calcite with oxalic acid derived from the metabolic activities of surface microflora, such as cyanobacteria. This paper provides the first record of weddellite in SA. The discovery of weddellite has a number of implications, the first being that the rock coating could potentially be used to conduct AMS analysis and thereby refine our understanding of the rock art chronology at Ngaut Ngaut and possibly at other similar heritage complexes in the mid-Murray region. A greater understanding of the potential rates of accumulation may also be useful for management purposes in terms of providing possible timeframes for the progressive deterioration of rock art at this and related sites.

In relation to management issues this research has also outlined areas of concern in relation to petroglyphs engraved

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into limestone in the mid-Murray that are covered with dark rock coatings. Minute unicellular organisms, apparently including cyanobacteria, were identified in one of the Ngaut Ngaut samples—a finding which is cause for concern because algal colonisation of limestone can contribute to exfoliation in the long-term by sheet spalling (an effect which appears to be occurring at Ngaut Ngaut). This finding poses a challenge to Hale and Tindale’s (1930:210) argument that the rock coating protects the art. Indeed, whilst a surface film may bind loose grains together and cement the rock art in the short-term, the longer-term effect of salt weathering and contraction and expansion seems to lead to exfoliation. Further, on the topic of crust microflora identification, it must be noted that much more research is required in the mid-Murray region. However, whilst potentially many specific taxa may be involved in such rock coatings, generalisations can be made about the consequent interaction of such microflora with the geological chemistry of the region.

Finally, whilst the Raman analysis conducted on particles from the dark rock coating in this study failed to produce any diagnostic peaks, Frost (2004) has observed more generally that oxalates can be readily determined by Raman microscopy. As such, despite our lack of success in this area, other researchers should still consider this method in their suite of analyses.

Acknowledgements

Rowl Twidale and Jennifer Bourne deserve significant acknowledgement for their assistance in this project. Their contribution to field trips, our geological understanding of the area and their encouragement to keep investigating the rock coating issues were vital to the project. A big thank you to all of the staff and students who have worked on the field school seasons during which some of the observations noted in this paper were made. Thank you also to staff at the Aboriginal Affairs and Reconciliation Division for advice on permit and permission issues. Thank you also to the South Australian Museum Archives’ staff for their assistance with archival images and documents. Acknowledgements are also due to Flinders University for providing some of the funds for this project through AR’s Re-Entry Fellowship. The Australian Institute of Nuclear Science and Engineering is acknowledged for RPF’s AINSE Research Fellowship. The authors also thank the Australian Microscopy and Microanalysis Research Facility at Flinders University. We are also appreciative of the comments made by the reviewers (Maxime Aubert, Noelene Cole and Jillian Huntley) as well as the Editors, which have served to improve this article.

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