C Sharples

University of Tasmania

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Paul M. Donaldson

Research Complex at Harwell

Michael Comfort

RTI International

Colin D. Woodroffe

University of Wollongong

I Houshold

RE Mount

Bureau of Meteorology

John R. Laurie

Geoscience Australia

David M. J. S. Bowman

University of Tasmania

Bryan Stait

Memorial University of Newfoundland

Michael Roach

University of Tasmania

Thomas S.N. Oliver

UNSW Sydney

Cooperative Institutions

University of Tasmania

Edith Cowan University

University of Queensland

Consejo Superior de Investigaciones Científicas

Commonwealth Scientific and Industrial Research Organisation

University of Western Australia

University of California, Berkeley

University of Adelaide

University of Wollongong

Australian National University

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National sediment compartment framework for Australian coastal management

Ocean & Coastal Management (2018)

B. G. Thom Ian Eliot Matt Eliot Nick Harvey David Rissik

Sedimentary budget

Landform

Coastal Management

Deposition

10.1016/j.ocecoaman.2018.01.001

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Citations (108)

The geology and landforms of Northeast Tasmania

C Sharples

The Northeast is a geologically distinctive region of Tasmania. The Northeast is founded on marine turbidite rocks (the Mathinna Group) intruded by granitic rocks. This assemblage is distinctly different from the contemporaneous shallow marine shelf carbonates and clastics found west of the Tamar. It was formed at some distance from the 'Western Tasmania Terrane' and was transported to its present location by movements along the Tamar Mobile Belt. Much of northeast Tasmania has been relatively uplifted during long periods of its subsequent history, with only thin sequences of younger Permian sedimentary rocks being deposited in the present highland areas. The Permian rocks were intruded by extensive sheets of dolerite magma in mid-Jurassic times at the start of the breakup of Gondwana. Landform evolution during the Tertiary Period followed the development of increased landscape relief due to block faulting in Cretaceous to Early Tertiary times. Fluvial processes have shaped the landscape during most of its subsequent development, although basaltic lavas tilled some valleys and altered drainage patterns during the Tertiary. An extensive area of the pre-Permian erosional surface has been exhumed and forms a prominent component of the present-day n01theast Tasmanian highlands. The higher peaks, capped by resistant remnants of the dolerite sheets, underwent accelerated erosion during glacial climatic stages. The arid climatic conditions of the last glacial stage allowed the formation of extensive dune fields on the Bass Strait plains, a portion of which are preserved on the north coastal platform. The heights of relict shorelines of last interglacial age suggest that northeast Tasmania has undergone greater Quaternary uplift than most of mainland Australia. Land use patterns in northeast Tasmania have been strongly influenced by distinctive topographies and soils on particular bedrock and landform systems. Since geology and landforms also influence the distributions of biological communities. the conservation of biodiversity in the Northeast faces the problem that, whilst those communities which are least disturbed and least endangered have the best statutory protection, those most endangered are likely to be those characteristic of the more heavily disturbed bedrock and Iandform assemblages which have been favoured for settlement and agriculture.

Marine transgression

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Identification and Management of Geoconservation Values in the Tasmanian Wilderness World Heritage Area

C Sharples

The development of geoconservation concepts and management practices in Tasmania, Australia, has been closely linked with the identification and protection of nature conservation values in the Tasmanian Wilderness World Heritage Area (TWWHA). The inundation of the outstanding glacio-fluvial landform of Lake Pedder for hydro-electric development in south-west Tasmania in 1972 was a major event in the history of environmental politics in Australia. In Tasmania it triggered the notion that landforms – and not just living things – should be a major focus of nature conservation. After two decades of political controversy the Tasmanian Wilderness World Heritage Area was inscribed on the UNESCO World Heritage List in 1989. Two of its key listed values were its possession of large areas in which geomorphic and soil processes (fluvial, karst, coastal and blanket bog) were ongoing in a way predominantly unmodified by contemporary human activities, and its possession of a range of relict glacial, glacio karstic, periglacial and uplifted coastal landforms and sediments providing the best southern hemisphere geomorphic record of the Late Cainozoic 'Ice Ages' phase of Earth history in a tectonically stable, temperate maritime environment. The significance of these values in the Tasmanian context has led to the development of geoconservation priorities focused on maintaining the natural geodiversity of landforms and soils, and on conserving natural rates and magnitudes of change in ongoing geomorphic and soil processes. This is in contrast to mainland Australia, where geological heritage work has historically had a much stronger emphasis on the preservation of bedrock features and exposures. However, landforms and ongoing geomorphic and soil processes are highly relevant to mainstream nature conservation since these underpin bioconservation, and this has made geoconservation easier for Tasmanian land managers to understand and perceive as relevant. Recognition of geoconservation values as key values underpinning the World Heritage listing of the TWWHA has made funding available for a variety of relevant research and management activities, including the following examples: – Monitoring and removal of incipient exotic dune grass infestations from TWWHA sandy coasts, since such infestations have significantly modified dune dynamics on other Tasmanian coasts and hence threaten natural coastal geomorphic processes in the TWWHA. – Innovative rehabilitation aimed at restoration of former natural hydrological processes associated with a quarry whose operation was degrading ongoing karst processes in the major Exit Cave system of the TWWHA. – Research into the effects of differing fire regimes on TWWHA blanket bog peat soils, which can be severely degraded by excessive firing yet are periodically burnt deliberately in some parts of the TWWHA for bioconservation management reasons. The TWWHA blanket bogs have World Heritage significance in their own right, and also play a major role in natural fluvial and hydrological processes in the TWWHA. – Monitoring of bank erosion caused by tourist boat wakes on the TWWHA Gordon River estuary, and development of techniques to minimise boat wake impacts. – Rehabilitation of mid-Holocene alpine lunette dunes damaged by former 'traditional' stock grazing and firing in the Central Plateau region of the TWWHA. Whilst much effort has been expended on researching and developing management practices aimed at protecting geoconservation values in the TWWHA, the same geomorphically focused conservation concerns have also led to significant measures to appropriately manage active karst systems, relict glacial landforms and other geoheritage in State forest and some other land tenures in Tasmania.

Landform

Glacial landform

Bedrock

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Relating shoreline behaviour histories to wave climate

C Sharples RE Mount

This paper describes a study funded by the Commonwealth Department of Climate Change and Energy Efficiency, and undertaken during 2010 – 2011 with the aim of improving capacity to assess coastal vulnerability to sea-level rise by building on existing tools including the Smartline national coastal geomorphic map dataset and the Coastal Vulnerability Index (CVI) previously developed in the USA. We assume that wave climate is most commonly the primary driver determining the physical behaviour of erodible shores, and further assume that past shoreline responses to wave climate will be a useful predictor of future response under conditions of rising mean sea level. We recognise that other factors such as tidal processes and regional variability in sea-level rise are also important factors governing shoreline response to sea-level rise, and seek to identify coastal environments in which these are equally or more important controls on shoreline response. Seventeen erodible shoreline study sites in both open and sheltered coastal environments were selected in Tasmania, the NSW coast, at Darwin, and in South Australia. Shoreline change histories on multi-decadal time scales at each site since the 1940s were mapped and quantified from time series ortho-rectified historic air photos. Swell and/or local fetch wave climates were modelled for each study site using SWAN and GREMO software respectively. The historic behaviour of each site was compared with wave climate modelling to determine the degree to which wave climate can explain observed shoreline behaviour at each site. Physically meaningful and statistically significant relationships between shoreline behaviour and modelled wave climate indices have been identified at some sites, whilst results from some other sites have demonstrated that factors other than wave climate appear to dominate shoreline behaviour in those cases. The outcomes of this study will contribute to the development of indices of physical coastal sensitivity that are conceptually similar to but more reflective of actual coastal processes than the CVI, and will identify further work needed to understand the behaviour of shores dominated by processes other than wave climate.

Fetch

Coastal erosion

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The durability of Tasmanian building sandstones

C Sharples

Tasmanian building sandstones have been almost entirely quarried from fluvial sandstones of the Early Triassic Quartz Sandstone Sequence and the Permian Lower Freshwater Sequence. These continue to be the only horizons considered prospective for new sources of high quality building sandstone. Technical data on all significant Tasmanian building sandstone sources is presented. There are three methods of assessing and predicting sandstone quality and durability in the built environment: 1) Inferring predicted stone behaviour from measurement of sandstone properties. 2) Accelerated decay tests. 3) Observed performance in existing buildings. Each method is subject to limitations. Optimum assessments are made by interpreting a combination of data from all three approaches, in the light of an understanding of the nature of sandstone properties and of the processes of sandstone decay. Investigation of the geological processes controlling the genesis of sandstone properties has led to the development of models to facilitate exploration for high quality building sandstones: Most jointing in Parmeener Supergroup sandstone is related to Mid-Mesozoic and Early Tertiary faulting. The areas most prospective for widely-jointed sandstones are predicted on the basis of known regional variations in fault densities. The bulk colour of sandstone is related to the content of iron-rich minerals in the sandstone, particularly vermiculite, smectite and chlorite, which oxidise to yield brown ferruginous coloring. Liesegang rings form in proximity to iron-rich basic igneous rocks, probably through weathering-related groundwater processes. For most building purposes, thick and massively-bedded sandstone is the ideal. There is no way of predicting the occurrence of such beds on a regional or local scale, except insofar as they are more prevalent in the stratigraphically lower parts of the Triassic Quartz Sandstone Sequence as a whole. Sandstone strength and porosity are functions of mineralogy and intergranular texture. The geological controls on these properties are discussed. The occurrence of superficial pachydermal fractures on natural outcrops is considered to be an indicator of sandstones having weak intergranular textures resulting in a high degree of dimensional instability. Smectite swelling clay is detrimental to sandstone durability. The proportion of smectite in sandstone varies markedly within individual outcrop areas, but on a larger scale there appear to be regional and possibly stratigraphic patterns in smectite occurrence. The smectite (together with vermiculite) is considered to have formed by alteration of volcanic dust deposited from ash clouds produced by contemporaneous volcanic sources to the southeast of the Tasmania Basin. Weathering of natural outcrops alters important sandstone properties, most importantly through near-surface kaolinisation. An exploration program for high quality building sandstones is proposed which takes account of this limitation, and of the exploration models developed in this work. The major contribution of this thesis is that an understanding has been achieved of the avenues of research which are necessary to further the development of models explaining the genesis of important quality and durability-related sandstone properties. These are listed.

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The Smartline - an effective coastal data mapping format

C Sharples RE Mount

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The tidal characteristics and shallow-marine seagrass sedimentology of Robbins Passage and Boullanger bay, far northwest Tasmania

Paul M. Donaldson C Sharples RJ Anders

This natural resource management research project was initiated by the Cradle Coast NRM, in response to the knowledge gaps identified by the Blue Wren Group in understanding elements of Robbins Passage-Boullanger Bay (RP-BB) coastal processes. The purpose of this study was to: • Improve the understanding of RP-BB tides, based on observational data, and • Investigate the carbon sequestration potential and palaeo-environmental evolution of RP-BB shallow seagrass beds, based on a set of shallow marine sediment cores. The key findings of this report are: • RP-BB receives strongly semi-diurnal meso-tides which vary in their range and time of arrival • Predicted mean spring tide ranges and total tide ranges were found to be 2.80 m and 3.15 m at Howie Island, 2.20 m and 2.63 m at Kangaroo Island, and 2.01 m and 2.42 at Welcome Inlet • The National Tide Centre’s modelled tide range was found to underestimate the tide range for eastern Boullanger Bay by approximately 30% • Three unique sedimentary deposits (i.e. facies) were identified in the sediment cores, interpreted as a Late Pleistocene alluvial/lacustrine deposit (SF1), Mid-Holocene intertidal or shallow subtidal sand flats (SF2), and Mid-Late Holocene seagrass associated deposits (SF3 • Large carbon rich sediment deposits exist beneath the subtidal seagrass meadows at RP-BB • RP-BB Posidonia australis dominated subtidal seagrass meadows are highly effective at sequestering carbon.

Tidal range

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Citations (4)

Potential Climate Change Impacts on Geodiversity in the Tasmanian Wilderness World Heritage Area: A Management Response Position Paper

C Sharples

Geodiversity

Position (finance)

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Citations (13)

Reply to: Punctuated transgression (?): Comment on Oliver, T.S.N., Donaldson, P., Sharples, C., Roach, M., and Woodroffe, C.D. “Punctuated progradation of the Seven Mile Beach Holocene barrier system, southeastern Tasmania”

Marine Geology (2018)

Thomas S.N. Oliver Paul M. Donaldson Michael Roach Colin D. Woodroffe C Sharples

Progradation

Marine transgression

Chronology

10.1016/j.margeo.2018.09.005

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Guidebook for the Australasian Cave and Karst Management Association Inc.

C Sharples

The north-west region of Tasmania encompasses a wide diversity of landscapes and karst environments. Along a broad coastal hinterland between Devonport and Smithton, rolling hills with extensive basalt soils comprises one of Tasmania's most richly productive agricultural regions. Within this region, Ordovician limestones exposed in some valley floors and flanks show extensive karst development at places such as Gunns Plains and Mole Creek, where three of Tasmania's four show caves are located. Further south towards Cradle Mountain, the same Ordovician limestones outcrop in the highland Vale of Belvoir whose unique moorland landscape is one of Tasmania's few alpine karsts. On the coast at Rocky Cape, another type of cave is exemplified by raised sea caves of Last Interglacial age that were excavated by wave action in quartzite coastal cliffs; these are significant for the evidence they contain of past Aboriginal occupation of this landscape.

Coastal plain

Geotourism

Outcrop

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