Geoheritage significance of three contiguous Holocene wetlands 161, 162, & 163 in the Becher Wetland Suite, south-western Australia

Semeniuk, Christine1, Semeniuk, Vic1,2

1V & C Semeniuk Research Group, , , 2Notre Dame University, Fremantle, Australia

The Becher Wetland Suite comprises a series of wetland basins located in inter-dune depressions on a Holocene prograded beach-ridge plain.  With progradation, the wetlands formed by the regional water table naturally rising into the inter-dune depressions.  As beach-ridge progradation is westerly, the inter-dune depressions (becoming wetland basins) generally young towards the west, with the oldest basins some 4500 years old, and the youngest < 900 years old.  Through the Becher region, the insertion of wetlands on the prograded beach-ridge plain, through generally younging westwards, in detail, is staggered because of the uneven topography of the depressions along their length.  For instance, wetlands 161, 162, & 163, the subject of this paper, all occur along an inter-dune depressions located on the 4500-year beach-ridge isochron (the oldest part of the beach-ridge plain) and, as such, ideally should be the same age and show the same history. However, they have a staggered history, with wetland 161 commencing accretion some 4350 years ago, wetland 162 commencing 4110 years ago, and wetland 163 commencing 2920 years ago.  All three basins filled with calcilutite.  However, with different ages and longevity of accretional history, and subject to differing small-scale temporal climate changes (in the order o 100 years of less) they exhibit different sedimentary history in terms of thickness of calcilutite, the relationship of calcilutite to underlying sand, diagenetic effects (such as dissolution of underlying carbonate sand, dissolution of Chara and sponge spicules, and patchy cementation of calcilutite), and the responses to fire.  This sequence of wetlands illustrates the complexities of wetland basin sedimentation.   As such, the contiguous wetlands 161, 162, & 163 are a system of international geoheritage significance.


Biography

Christine Semeniuk is a Director of VCSRG, a Research & Development Corporation.    Graduated from the University of Sydney in 1969, she was awarded a PhD from Murdoch University in 2003. Christine arrived in Western Australia 50 years ago, undertaking research into wetlands of Western Australia, and has over 30 peer-reviewed publications in wetland science and geoheritage, including the geoheritage values of wetlands of the Swan Coastal Plain. Christine is a founding member of the NGO the Wetlands Research Association inaugurated in 1999.

Patina: A microscopic feature of palaeo-environmental and geoheritage significance

Clifford, Penelope1, Semeniuk, Vic1,2

1Notre Dame University, Fremantle, Australia, 2V & C Semeniuk Research Group, ,

Patina is an ultra-thin crust of silica or silica and carbonate that is developed on glass and, while it best developed on anthropogenic glass, it provides important information on products and processes associated with weathering of glasses in general.  It is common in modern environments, though variable in expression dependent on environmental setting, and it has been recorded on pre-Mediaeval and Mediaeval artefacts.  Anthropogenic glass is geochemically unstable and, as such, it corrodes relatively rapidly (within years), generating a variety of weathering crusts of different thicknesses, and various internal structures.  The type of patina that is developed depends on the glass composition, the type of soil it is embedded in, the hydrochemistry of the soil water, climate setting, and whether the glass is located in an inland vadose zone or phreatic zone, a maritime coastal zone, or a submarine environment. The patina crusts are < 10 µm up to 100 µm, thickening with age. The solutional relationship of the patina to the glass varies from straight, undulating, irregular, to cuspate and, internally, shows structures of colloform to undulating lamination, parallel lamination, massive to mottled patterns, micro-brecciation, shrinkage cracks, and infiltrated dust-sized minerals, all reflecting and recording a history of solution and precipitation, and variation in climate. For vadose environments, the main agents in the patination is alternating wet and dry vadose conditions, and alternating acid and alkaline vadose conditions that result in precipitation of an amorphous silica ‘gel’ that forms silica laminae, its layer-parallel shrinkage, and the precipitation of calcite laminae.  While modern patina and historic patina have been documented from the various climate, hydrochemical, and pedogenic environments, the results are widely applicable to understanding and unravelling the weathering of natural materials such as obsidian, chert, and volcanic glasses – in this context, it conforms to the geoheritage category of ‘modern processes’ and provides a record of modern processes and products in the weathering of natural glass and glass-like materials.


Biography

Vic Semeniuk is a Director of VCSRG, a Research & Development Corporation. Awarded a PhD from the University of Sydney, a UWA Postdoctoral Fellowship, and the Queens Postdoctoral Fellowship in Marine Science, as a multi-disciplinary research scientist, Vic has over 160 peer-reviewed publications in the geology, geomorphology, and geoheritage, as well as in coastal science, environmental science, and conservation ecology (estuaries, mangrove, wetland, coastal dunes, soldier crabs). Vic arrived in Western Australia 50 years ago, initially with a position at The University of Western Australia, and continues to teach and supervise postgraduate students as an Adjunct Professor at the University of Notre Dame and Murdoch University. Vic is a founding member in 2019 of Geoheritage Australasia, and in 1999 of the Wetlands Research Association. Inc.

Recognising and preserving mineral diversity: An updated catalogue of type mineral specimens in Victoria’s State collections

Lindenmayer, Oskar1

1Museums Victoria, Melbourne, Australia

Type mineral specimens are designated by the International Mineralogical Association (IMA) as the physical standards by which newly discovered mineral species are defined. They represent the benchmarks against which the word’s mineral diversity can be recognised and studied. Each type mineral specimen is a globally significant element of movable natural heritage and forms an irreplaceable resource for researchers in the fields of mineralogy, crystallography and materials science. Despite their importance, the management of these specimens has historically lacked transparency.

Museums Victoria holds approximately half of the type mineral specimens in Australian institutions. The most recent edition of the global catalogue of type mineral specimens, prepared under the direction of the IMA Commission on Museums, lists 98 specimens as lodged with Museums Victoria, of which 45 are from Australian localities and 53 are from overseas localities. This catalogue also lists the whereabouts of 12 specimens from Australian localities as unknown. In contrast to the global catalogue, Museums Victoria’s internal catalogue includes 125 type mineral specimens, of which 59 are from Australian localities and 66 are from overseas localities. There are also a number of discrepancies between the two catalogues for specimens that appear on both, including type status (ie. whether the specimen is a holotype, cotype or neotype) and registration number.

To resolve these issues, a review of the information available in publications, Museums Victoria records and correspondence, and minutes from meetings of IMA Commissions has been undertaken for each specimen. Where necessary and practical, authors of new mineral descriptions have been contacted for further information. A methodology has been developed to identify legitimate type specimens and appropriately categorise them by their type status. In a departure from previous attempts to document type mineral specimens in Victoria’s State collections, areas of uncertainty or missing information for specimens are flagged and explicitly discussed.

The sources of the majority of the discrepancies between the global and internal catalogues were found to be either publically undocumented transfers from other institutions or incomplete information having been given in the original publications of new mineral descriptions. Amongst the discrepancies resolved was the identification of Museums Victoria as the lodging institution for five of the type specimens listed as having unknown whereabouts in the global type catalogue. In the absence of a formal mechanism for reviewing details or reporting transfers of type mineral specimens, periodical review and publication of catalogues by the institutions that hold them is necessary for the ongoing management of these most significant parts of mineral collections. It is hoped that by undertaking this review in a transparent manner, and making the results and methodology publically available, other institutions will be encouraged to do the same.


Biography

As Collection Manager, Geosciences, at Museums Victoria, Oskar is responsible for managing Victoria’s State collections of minerals, gemstones, rocks, meteorites, and tektites.

This involves preserving and organising the collection, maintaining and improving the digital collection database and facilitating access of the collections for the purposes of research, education, and exhibition.

A geoheritage treasure – a case study of the Hornsby Diatreme

Semeniuk T A1,2

1Western Sydney University, The College, Quakers Hill, Australia.  email: t.semeniuk@westernsydney.edu.au

The quarrying for bluestone at the Hornsby Quarry Site exposed a > 40 m-deep cross-section of a volcanic diatreme, showing a volcanic neck extruding through Sydney Basin sediments, complete with volcanic features visible at many scales, with post-volcanic features related to magma and gas extrusion at various depths, and with different host rocks. Globally, there are very few instances of such excellent exposure, revealing a full range of macroscale to microscale features in three dimensions. It is arguable that this exposure alone, makes it a site of international geoheritage significance.  Using the Geoheritage Tool-kit, applied at various scales shows that this diatreme is internationally to nationally significant.  For example, at the macroscale, there dish beds in all orientations of the quarry walls are visible, giving a three-dimensional picture of its structure, reflecting its volcanic accretion and later caldera collapse.  At the mesoscale, where breccia beds, bombs, and surge layers are visible, these show how the magma interacted with various host rocks and other post-volcanic processes that occurred prior to solidification.  Finally, at the microscale, lapilli (including accretionary lapilli), chilled margins and carbon-rich xenoliths are evident in hand specimen.  As such, this Quarry is a unique site worldwide. In fact, the Quarry, exposing the volcanic pipe of the Hornsby Diatreme, offers a snapshot in time of the Sydney Basin, preserving its volcanic and post-volcanic history on the quarry walls.


Biography

Trudi Semeniuk is a multidisciplinary scientist in the fields of general geology, metamorphic geology, geoheritage, wetland-, mangrove-, foraminiferal-, and tidal-flat sedimentology and ecology.  Her work experience is manifold ranging from fieldwork for VCSRG (a Research & Development Corporation), and a Research Officer for ANU, CSIRO, and Kings Park Botanical Gardens. More recently Trudi has focused on reviewing sites of geoheritage significance listed on, the now archived, Register of the National Estate (NSW) and work as a scientific editor.  Trudi was awarded a PhD from the Institute of Mineralogy and Petrography, ETH Zurich in 2003 in a study of Alpine mylonites, and completed a Postdoctoral Fellowship in 2004-2006 in aerosol chemistry at Arizona State University.  Trudi is active in Geoheritage, and is the co-convenor for the NSW Division for Geoheritage in the Geological Society of Australia.

The status of geoheritage and geoconservation in Australia

Creswell, Ian1

1University of Newcastle, Callaghan, Australia

The protection of Australia’s natural heritage has been ongoing since the 1870s in every state and territory, however, efforts to identify and conserve important sites of geoheritage significance have had limited success.  This presentation reviews the policies and legislation governing geoheritage and geoconservation in all Australian jurisdictions and shows that there are inconsistencies and inadequacies in the processes to identify and protect areas of geoheritage significance.  Each state and territory has differing emphases on geoconservation and different degrees of success in achieving geoconservation goals.  In 2015 the Australian Government released the Australian Heritage Strategy as the overarching framework for the identification, management, and protection of Australia’s heritage across all levels of government and community.  While in recent years there have been a few ad hoc successes related to national heritage or to state heritage, it is not clear the strategy is working.  There is an urgent need for a nation-wide systematic approach to identifying representative geoheritage sites, and to enact processes for their protection.


Biography

Dr Cresswell is the co-Chair of the national State of the Environment report, and Chair of the Western Australian Biodiversity Science Institute. He has extensive experience working in environmental science in biodiversity conservation and discovery, oceans governance, fisheries management, wildlife regulation, and protected areas, including geoheritage. He has led major programs in CSIRO both in marine science and terrestrial and freshwater ecology science. Previous to this Ian worked within the Australian Government leading oceans management, sustainable fisheries assessments, international wildlife management, and the Australian Biological Resources Study. In collaboration with the V & C Semeniuk Research Group, Ian has studied coastal systems, including coastal dunes, estuaries, mangroves systems, and tidal flats, towards their management and assessing their geoheritage values.  In relation to geoheritage, Ian has a strong interest in geoconservation, policy, and legislation, and maintains an ongoing research interest in multiple-use management and coastal systems.

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

As a broadly based professional society that aims to represent all Earth Science disciplines, the GSA attracts a wide diversity of members working in a similarly broad range of industries.

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