Anthony R Milnes
The University of Adelaide, Department of Earth Sciences, Department Member
- PhD on Cambrian granites and metamorphics in 1973. Subsequent post-doc at Monash University on phosphate mineralogy.... morePhD on Cambrian granites and metamorphics in 1973. Subsequent post-doc at Monash University on phosphate mineralogy. Research with CSIRO Land & Water over many years since 1978 on mineralogy and geochemistry of weathering in soils and landscapes (silcretes, calcretes, ferricretes). Initiated CSIRO multi-Divisional research program on minewastes and mine landforms focussed on rehabilitation strategies from mid-1980’s. Joined ERA/Rio Tinto in 1996 until 2010 as General Manager Environmental Strategy, focussed on Ranger & Jabiluka. Visiting Research Fellow in Earth Sciences at the University of Adelaide since 2012. Current research interests are weathering and landscape evolution.edit
The excursion aims to show how the morphologies of silicified sands in the Sables de Fontainebleau (Oligocene, Paris Basin) reveal the hydrological conditions that prevailed at the time of their formation in the Quaternary. It is a... more
The excursion aims to show how the morphologies of silicified sands in the Sables de Fontainebleau (Oligocene, Paris Basin) reveal the hydrological conditions that prevailed at the time of their formation in the Quaternary. It is a completely new approach which ultimately makes possible a demonstration of the presence of thick frozen soils (permafrost) in the Paris Basin during Quaternary glacial periods and provides proxies for determining the minimum depth reached by the permafrost.
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A model for groundwater silicification within the Fontainebleau Sands in sub contemporary landscapes was first proposed 35 years ago but has now been substantially updated with reference to new research that explains silica precipitation... more
A model for groundwater silicification within the Fontainebleau Sands in sub contemporary landscapes was first proposed 35 years ago but has now been substantially updated with reference to new research that explains silica precipitation during periglacial climate conditions. Herein we focus on observations that point to a deep permafrost which controlled the hydrology of paleolandscapes in the Paris Basin during Quaternary glaciations.
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Coloured heavy mineral sands are a conspicuous yet somewhat ephemeral feature on the surface of many beaches around Gulf St Vincent and in Encounter Bay in South Australia. The ultimate origin of the minerals continues to be investigated,... more
Coloured heavy mineral sands are a conspicuous yet somewhat
ephemeral feature on the surface of many beaches around Gulf St
Vincent and in Encounter Bay in South Australia. The ultimate origin
of the minerals continues to be investigated, but they are known to
be important constituents of an extensive suite of Carboniferous to
Permian glacigene sediments deposited over most of the region.
They occur in Palaeogene palaeochannel sands as well as within
overlying Pleistocene alluvial sediments and soils. It is the continued
erosion of these sediments that has fed the heavy minerals into
modern terrestrial landscapes and concentrated them in small-scale
placer sands on the beaches around Gulf St Vincent.
ephemeral feature on the surface of many beaches around Gulf St
Vincent and in Encounter Bay in South Australia. The ultimate origin
of the minerals continues to be investigated, but they are known to
be important constituents of an extensive suite of Carboniferous to
Permian glacigene sediments deposited over most of the region.
They occur in Palaeogene palaeochannel sands as well as within
overlying Pleistocene alluvial sediments and soils. It is the continued
erosion of these sediments that has fed the heavy minerals into
modern terrestrial landscapes and concentrated them in small-scale
placer sands on the beaches around Gulf St Vincent.
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ABSTRACTConspicuous chert horizons occur as discontinuous bands and isolated nodules in dolostones in the Eocene Dammam Formation, which is exposed in the southeast of Kuwait. The Formation has never been deeply buried, and so chert... more
ABSTRACTConspicuous chert horizons occur as discontinuous bands and isolated nodules in dolostones in the Eocene Dammam Formation, which is exposed in the southeast of Kuwait. The Formation has never been deeply buried, and so chert formation is likely to have resulted from silicification processes at or near the land surface. Erosional reworking of the chert constrains its formation to a time period between the late Eocene and the Mio-Pliocene. As there is no significant source of silica in the dolostones, the chert was formed from silica imported from other sources. This process, together with the specificity of chert to particular non-bedding horizons, suggests that silicification is related to discrete locations of the groundwater table during landscape incision and resultant groundwater discharge in the region. Detailed petrographical studies demonstrate that “chertification” was initiated by precipitation of nanoglobules of silica (opal-A) from supersaturated groundwater solut...
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The Troubridge Basin in South Australia is a late Paleozoic sedimentary basin, extending from the Coorong area across Fleurieu Peninsula and Kangaroo Island to Yorke Peninsula (Alley and Bourman 1995; Fig. 1). The basin contains the Cape... more
The Troubridge Basin in South Australia is a late Paleozoic sedimentary basin, extending from the Coorong area across Fleurieu Peninsula and Kangaroo Island to Yorke Peninsula (Alley and Bourman 1995; Fig. 1). The basin contains the Cape Jervis Formation, which crops out extensively in these areas. The formation is also widely distributed in the subsurface below Yorke and Fleurieu peninsulas, Gulf St Vincent, Investigator Strait, Backstairs Passage, the Coorong area, Kangaroo Island and on the continental shelf to the east of Kangaroo Island (Alley and Bourman 1995). In some areas the formation forms a blanket of sediment and, in others, significant thicknesses are preserved in glacially eroded troughs or local tectonic depressions.
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ABSTRACT Interrelated themes within the tour are principally landsurfaces and landscape evolution; clays and other weathering and alteration minerals in sediments, saprolite and soil materials; and silicification phenomena, including... more
ABSTRACT Interrelated themes within the tour are principally landsurfaces and landscape evolution; clays and other weathering and alteration minerals in sediments, saprolite and soil materials; and silicification phenomena, including precious opal. The tour is written in such a way that it can be followed while travelling, and hopefully provides sufficient references to distances and landmarks to enable "tourists" to locate themselves readily. The distances to be travelled are vast and the time-frame is short, and so the opportunity for stopping at unscheduled sites is unfortunately limited. We hope you enjoy the highlights we have selected. Features of particular interest include: clay minerals; palaeosurfaces; salinas; dunes; desertic soils and stone pavements; gjlgai; carbonates and salts; Andamooka precious opal, pedogenic and groundwater silcretes, deep bleaching and weathering Lake Eye; mound springs; treeless pains of cracking clays, with gypsum and epsomite; Coober Pedy precious opal, pedogenic and groundwater silcretes, deep bleaching and weathering, termite burrows, alunite, and red-brown hardpans; Stuart Range scarp and breakaway country, and maghemite gravel lags. Palaeosurfaces: the Mesozoic Arcoona Surface developed on Proterozoic and Cambrian sediments, and covered by non-marine and marginal marine Cretaceous sediments; a Late Cretaceous to Early Tertiary landsurface; a later Tertiary landsurface characterised by pedogenic silcrete, the dissection of which may be related to a series of groundwater silcretes; a complex of younger landsurfaces approaching regional baselevel. Landscape processes: rolling stony downs, with carbonate and salts, gilgai and swamps; sand dunes and eolian processes; landsurface remnants like mesas and plateaux, with breakaways and other forms of landsurface dissection and degradation; pedogenic silcretes and collapse structures; weathering processes and the deep bleached profile, groundwater silcretes, and the influence of biological processes including termite activity; hardpans (duripans), silica, gypsum and carbonates; mound springs; salinas and the regional watertable. Clays: character of clays in the contemporary soil mantle, carbonates and salts; minerals of the deep bleached and weathered profile, including opal and alunite.
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Studies of iron-rich crusts, commonly called 'laterite' in Australia, but here termed 'ferricrete', have identified different forms and various modes of iron enrichment. In outcrop and in hand specimen, these ferricretes are massive to... more
Studies of iron-rich crusts, commonly called 'laterite' in Australia, but here termed 'ferricrete', have identified different forms and various modes of iron enrichment. In outcrop and in hand specimen, these ferricretes are massive to vesicular, pisolitic, nodular, slabby or vermiform in character. Some have inherited fabrics from pre-existing sediments or bedrock metasediments; others are cemented lags of ferruginous clasts or pisoliths, probably formed by physical reworking in terrestrial, sedimentary and pedogenic environments. The different forms of ferricrete exhibit differences in micromorphological characteristics, mineralogy and chemical composition that reflect the nature of the parent material, the environmental conditions during iron impregnation, and subsequent transformations during landscape evolution. Most profiles are stratigraphic sequences recording a succession of sedimentary deposits of different ages subjected to long periods of continuous weath...
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This field excursion was developed from a more comprehensive Field Workshop on Silcretes held in August, 1985. In planning that venture, it was considered that significant benefits could be gained by having people from many disciplines... more
This field excursion was developed from a more comprehensive Field Workshop on Silcretes held in August, 1985. In planning that venture, it was considered that significant benefits could be gained by having people from many disciplines look at silcretes in the arid zone of Australia where there are good exposures of these materials. The same concept applies to arid zone soils and landscapes, once the preserve of several eminent soil scientists in Division of Soils but a much neglected field of study in latter years. Hence the present excursion. The opportunity to undertake new work in the arid northern lands of South Australia is now presented largely because of the current geological mapping programme of the South Australian Department of Mines & Energy. The maps being produced at 1:250 000 scale incorporate many observations on the regolith, particularly the nature of landforms, the character of soils and palaeosols, the distribution of gilgai, and the composition of materials for...
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The notion of surficial silicifications, due to specific morpho-climatic conditions, was understood by geologists at the beginning of the XXth century, by study of the wide arid areas of South Africa and Australia. There are the studies... more
The notion of surficial silicifications, due to specific morpho-climatic conditions, was understood by geologists at the beginning of the XXth century, by study of the wide arid areas of South Africa and Australia. There are the studies of Kalkowsky (1901) and Stortz (1928) on the Kalahary Desert, of Lamplugh (1907) in Rhodesia, which created the name silcrete for these formations, and Woolnough (1927) in central Australia. In these countries, siliceous duricrusts constitute the capping of plateaus and mesas and affect every type of rocks. The relationship of these duricrusts with the landscapes led these authors to consider them as modern. The notion of surficial silicifications linked to arid climates then appeared obvious. Subsequently, numerous occurrences of silcretes have been described, either capping arid landforms or interbedded in the geological formations. All these occurrences however are ancient, geological ones. Until recently no modem actively developing profile was k...
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A lateritic profile developed on sands in South Australia shows strong similarities to a Ferric Podzol in profile development, and the yellow kaolinitic cements of its lower B horizons form strongly birefringent layered coatings, closely... more
A lateritic profile developed on sands in South Australia shows strong similarities to a Ferric Podzol in profile development, and the yellow kaolinitic cements of its lower B horizons form strongly birefringent layered coatings, closely matching the allophanic cements of a contemporary podzol. It is proposed that this lateritic profile is a fossil podzol, in which the original allophanic deposits have transformed to kaolinite. The profile is perhaps unique in that the weathering products (dominantly kaolinite and goethite, with a trace of gibbsite) are all illuvial, and not residual. In the light of these observations and published evidence, the role of mobile aluminium in lateritic landscapes is discussed, and the likely forms of its precipitates assessed.
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The transformation of Fe, Mn and Al during 28 weeks of oxidation in an acid sulfate soil from the Northern Territory, Australia, were determined in a laboratory incubation experiment. Chemical and magnetic analyses showed that iron in... more
The transformation of Fe, Mn and Al during 28 weeks of oxidation in an acid sulfate soil from the Northern Territory, Australia, were determined in a laboratory incubation experiment. Chemical and magnetic analyses showed that iron in pyrite was transformed to an Fe(III) oxyhydroxide phase with fine magnetic grain size, and water-soluble Fe(II) and Fe(III). The iron became resistant to extraction with citrate-dithionite-bicarbonate (CDB) and oxalate after 20 weeks of oxidation. Mn and Al compounds also underwent changes. Both elements showed transformation from forms not extracted by CDB and oxalate to extractable forms. This showed that silicate clay minerals were dissolved by acidic decomposition. Scanning electron microscope-X-ray dispersive studies showed that regions of clay minerals surrounding oxidizing pyrite framboids were subjected to dissolution. -from Authors
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Deep bleached weathering profiles are common facies in the regoliths, and are frequently associated with paleosurfaces. These profiles possess characteristics of acidic alteration in groundwater environments, and have developed in some... more
Deep bleached weathering profiles are common facies in the regoliths, and are frequently associated with paleosurfaces. These profiles possess characteristics of acidic alteration in groundwater environments, and have developed in some places to considerable depth. Deep bleached profiles are well developed beneath siliceous and ferruginous-aluminous duricrusts of Australia, and bleached facies are also widely distributed in several Tertiary formations in France. The characteristics of these materials provide an opportunity to postulate mechanisms which have led to their development, and also to establish their significance regarding paleoclimate and paleolandscape reconstructions
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Interrelated themes within the tour are principally landsurfaces and landscape evolution; clays and other weathering and alteration minerals in sediments, saprolite and soil materials; and silicification phenomena, including precious... more
Interrelated themes within the tour are principally landsurfaces and landscape evolution; clays and other weathering and alteration minerals in sediments, saprolite and soil materials; and silicification phenomena, including precious opal. The tour is written in such a way that it can be followed while travelling, and hopefully provides sufficient references to distances and landmarks to enable 'tourists'; to locate themselves readily. The distances to be travelled are vast and the time-frame is short, and so the opportunity for stopping at unscheduled sites is unfortunately limited. We hope you enjoy the highlights we have selected. Features of particular interest include: clay minerals; palaeosurfaces; salinas; dunes; desertic soils and stone pavements; gjlgai; carbonates and salts; Andamooka precious opal, pedogenic and groundwater silcretes, deep bleaching and weathering Lake Eye; mound springs; treeless pains of cracking clays, with gypsum and epsomite; Coober Pedy pre...
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The Ranger Uranium Mine in the Northern Territory, Australia has been depositing tailings into its 170 m deep No 1 pit since 1996. Potential slow consolidation of tailings deposited in such a deep pit has been a primary concern in terms... more
The Ranger Uranium Mine in the Northern Territory, Australia has been depositing tailings into its 170 m deep No 1 pit since 1996. Potential slow consolidation of tailings deposited in such a deep pit has been a primary concern in terms of tailings management at the mine. In order to develop an optimum management plan for the operation, a program involving in situ instrumentation and monitoring was implemented to investigate the behaviour of tailings deposited in the pit. The present paper reports on the behaviour of tailings deposited in the pit based on the monitoring data at the early stage of the operation.
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Comprehensive surveys and mapping of the vegetation on a number of areas selected for possible future mining of phosphate on Christmas Island, Indian Ocean, in concert with an evaluation of its ecology, enabled an assessment of potential... more
Comprehensive surveys and mapping of the vegetation on a number of areas selected for possible future mining of phosphate on Christmas Island, Indian Ocean, in concert with an evaluation of its ecology, enabled an assessment of potential impacts of disturbance. The research targeted the possible impacts on forest types as well as on the occurrence and distribution of EPBC-listed and other significant flora. Mining has not proceeded but the unique dataset provides new information on the floral ecology on this isolated seamount, demonstrates the effectiveness of a rigorous strategy for establishing baseline conditions, and informs practical approaches for both protecting significant flora and re-establishing key revegetation types in areas of significant land disturbance.
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Effective and sustainable restoration of significantly disturbed landscapes, particularly mined landscapes, is technically difficult and almost never achieved. However, it is possible to sustainably revegetate mined lands if there is a... more
Effective and sustainable restoration of significantly disturbed landscapes, particularly mined landscapes, is technically difficult and almost never achieved. However, it is possible to sustainably revegetate mined lands if there is a suitable understanding of the key attributes of the post-mining environment and of the vegetation composition and ecology of appropriate analogue areas. On Christmas Island, the mined phosphate is actually the substrate for natural vegetation establishment and growth. Post-mining karst landscapes provide completely different environmental conditions for plant growth. A detailed review and analysis of the floristics, ecology and structure of vegetation on Christmas Island, together with data on secondary and natural successional pathways following mining and other disturbances, has been undertaken over several years and provides the basis for a self-sustaining rehabilitation strategy based on six guiding principles.