Margaret Brocx

The Boronia Ridge palusmont, Walpole, in southern Western Australia, is situated in the most humid part of the State. It was a unique hilltop wetland complex and the only one of its type in the State. On its margins, the area also supports the ancient sedge Reedia spathacea, a Gondwanan relict endemic to humid southern Western Australia and the Walpole region and a plant that was ultimately recognised as being of national significance and protected under Australia’s strongest conservation law, the Environment Protection and Biodiversity Act (1999). However, prior to the geoheritage and biodiversity values of the area being known, in the late 1980s, a pristine scenic area west of Walpole, adjacent to the Walpole River and Walpole Inlet, classified as a Class A national park, was earmarked for urban development, in spite of there being “very little demonstrated requirement for land in Walpole”. This appeared to be as a result of poor land-use planning, since the urbanisation proposed was to be located on the Walpole River delta and wetlands. Urban infrastructures would also impact on adjoining wetlands and the Walpole Inlet System. With new information available in relation to the soils, wetlands, and environmental values of the area, in 1993, community groups and scientists combined, at a public Local Government meeting, to demonstrate that the proposed urban development, referred to as Lot 650, and later Boronia Ridge, with its above-land surface wastewater treatment, was inappropriate, both from an engineering perspective and due to the high conservation values of the area. With the support of the local government of the day and expert scientists who confirmed local concerns, the community engaged in a 7-year conflict with the development proponent, government agencies involved in decision making, and politicians of the day. Ultimately, the use of state-of-the-art science and traditional geomorphic, stratigraphic, hydrological, and geoheritage principles failed to prevent the urbanisation of the area in favour of preserving the whole area as a wetland complex. The following three reasons for this failure are identified: 1. political, rather than science-based decision making, 2. government agencies staffed without the necessary training in biological or earth sciences to make informed decisions, and 3. little attention to environmental concerns due to a bias towards development. Walpole, with its population of 400, moved from a low priority on the wastewater treatment priority list in Western Australia to a high priority on the deep sewerage priority list to accommodate a proposed residential development.

Located in south-western Australia in a distinctive setting sedimentologically, oceanographically, climatically, biologically, and sea-level history context, the Becher Point Cuspate Foreland is globally unique, and is a site of International Geoheritage Significance that has the potential to be developed as a Geopark. The cuspate foreland is part of an extensive shore-parallel Holocene coastal sand system that forms the seaward edge of the Swan Coastal Plain and eastern border of the Rottnest Shelf. It is the largest cuspate foreland complex in Western Australia and one of the largest in the World. Sedimentary accretion in the region began some 7000 years BP with a sea level + 2 m AHD. Since then, attended by a progressive climate change, sea level has steadily fallen to its present position, and sedimentation has built a coastal plain of low beach ridges with wetlands in the swales. Sedimentologically and stratigraphically, the cuspate foreland developed by seagrass bank accretion shoaling to the strand to form beach and beach-ridge/dune deposits capped in the swales by wetland deposits. Key features of the Cuspate Foreland are (1) the accreted Holocene beach-ridge plain, (2) the evolution of Holocene swale wetlands, (3) the Holocene sea level history, (4) Holocene climate history as recorded in the wetlands, and (5) a host of small-scale geological phenomena. The complex of beach ridges and swale wetlands is the basis of a geopark in which coastal plain evolution, wetland evolution, Holocene sea level history, and Holocene climate changes can be explored and explained essentially in an outdoor Museum. To illustrate the richness of the natural history information, from macroscale to microscale, embedded in the Becher Point Cuspate Foreland, we choose, as case studies, two aspects of the area and describe them in a holistic and multi-scalar manner for education and research, and potential thematic geotours.

Unlike other estuaries Nationally in Australia, the Walpole-Nornalup Inlets is unique complex twin-basin ria estuary in the most humid part of Western Australia. The estuary fronts the oceanographically-dynamic Southern Ocean and, with the high annual rainfall, it provides a range of estuarine landforms, estuarine peripheral wetlands, a dynamic sand barrier that records climate changes and, with its microtidal setting, it provides examples of complex riverine-to-marine dynamics such as intra-basinal gyring. A range of geological to estuarine features that are of geoheritage significance and available for exploration and explanation as geotrails include: (1) the Precambrian geology, (2) the stratigraphy of the Cainozoic Werillup Formation, (3) Cainozoic weathering, sedimentation, and climate history, with a very wet climate to produce erosionally-resistant quartz grain lags, (4) Cainozoic to Quaternary formation of a rock tombolo, (5) the complex estuarine shorelines and history, and (6) complex estuarine processes and history. As an ensemble of geological and other natural history features, Walpole-Nornalup Inlets system also provides a case study of a systematic approach, using the Geoheritage Tool-kit, of identifying and evaluating different natural values. This forms the foundation for to baseline monitoring (for environmental management) and tourism to explore through geological time the natural history of this geologically and biologically rich location.

This issue on Geoheritage and Geoconservation derives from presentations at the Australian Earth Science Convention held at the Adelaide Convention Centre, Adelaide South Australia (June 2016), the Linnaean Society of New South Wales Belubula Conference in Bathurst, New South Wales (September 2015), and an invited keynote contribution that brings together a diversity of papers capturing the breadth and scope of Geoheritage and Geoconservation in Australia...

The Ordovician Daylesford Limestone at Bowan Park and the Fossil Hill Limestone at Cliefden Caves have diagenetic and pedogenic features of microkarst, paleosols and calcrete associated with subaerial disconformities in their stratigraphic sequences, all of which, as an ensemble, have global geoheritage significance. The original shelly limestones, lime mudstones, and coralline limestones have selectively dissolved to form vugular limestone whose cavities have filled with sparry calcite and/or crystal silt. The limestones also have been calcretised to develop massive and laminar calcrete and calcrete ooids. Below disconformity surfaces are bleached limestone, crystal-silt and spar-filled fossil moulds and enlarged moulds, micro-breccia-filled moulds and fissures filled with crystal silt, calcrete pellets and calcrete ooids. The disconformity surfaces are irregular or undulating interfaces between lithologies, fissures and fissure-fills, and calcrete. Above disconformities there are limestone lithoclasts, remanié fossils, calcreted limestone, veined limestone, calcrete ooids, laminated calcrete, lithoclast grainstone, or calcrete-ooid grainstone, and lithoclasts with fossils moulds filled with crystal silt and/or spar. The lithological, stratigraphic and possibly landscape differences, make the subaerial diagenesis/pedogenesis in the Daylesford Limestone subtly different to that of the Fossil Hill Limestone. Subaerial disconformities and associated diagenesis/pedogenesis, as recorded in these formations, are not widely reported globally nor well represented in Ordovician limestones. The microkarst features provide insights into the types of subaerial diagenesis/pedogenesis during the Ordovician and into climate, landscape setting, paleohydrology, and groundwater/rainwater alkalinity. Consequently, the story of the Ordovician microkarst, paleosols and calcrete ooids is unique and globally of geoheritage significance as examples of subaerial alteration in an ancient high-rainfall, tropical climate volcanic island environment in a tectonically active region.

Equivalent in principle to type localities and type specimens in biology and paleontology, geological type sections and type localities, whether for sedimentary, metamorphic or igneous units, are critically important sites as long-term reference and research localities and for geo-education of students. Unlike type specimens that are housed in museums or established institutions of learning, most geological type sections and localities are in field settings and, if they are not located in National Parks or other reserves with some legislated protection, run the risk of being destroyed, inundated, buried by earthworks or otherwise modified. The history of the geological sciences in Australia is such that a number of type localities, or stratigraphic type sections, have been destroyed by local government actions, or developers through lack of knowledge of their importance, or lack of knowledge of their existence. Examples of the severe modification or loss of type sections include those of the Maxicar beds, the Tims Thicket Limestone and the Eaton Sand. The UK, a leader in the field of Geoconservation and with a number of global stratotype section and point locations as well as many other type sections identified within its borders, provides models for preserving and managing important geological sites and type sections. Whole-of-government and local governments are involved in the registering and protection of important geological sites. Aspects of the UK model may be adapted to help secure geological type sections and localities in Australia. While some type sections and heritage localities are already protected, to improve the level of protection for more sites we propose a long-term, multi-pronged approach: creation of an inventory of all nominated locations; registration of appropriate sites at Local, State or Federal government levels, where current legislation allows; education of landowners and land managers, both government and non-government to highlight the importance of type sections to science; and securing more geological type sections and localities in some form of reserve.

In identifying sites of geoheritage significance, commonly there has been an emphasis on the larger-scale features. However, the story of geology and the significant features that are critical to unravel geological processes and geological history are commonly small in scale. This contribution focuses on bubble sand and bubble-sand structures as features that are small-scale but nonetheless important to geology, and hence are of geoheritage significance. Bubble sand and bubble-sand structures are ubiquitous on modern beaches and tidal flats, occurring in the uppermost tidal zone of sandy beaches, as a distinct layer in a shoaling beach-to-dune stratigraphy, and are a diagnostic indicator of upper-tidal conditions where a rising tide and a concomitantly rising water-table interacts with the upper swash-zone wave processes. On sandy tidal flats, bubble sand and bubble-sand structures may occur in the mid- to upper-tidal zones; here they are also diagnostic indicators of tidal conditions, forming during a rising tide where a rising water-table forces air upwards to be trapped in moist sand. If found in ancient sequences, bubble-sand structures are a powerful environmental indicator of tidal conditions and, for beach sequences, an indicator of the high-tide level and sea level. Bubble-sand structures have been found in a number of ancient sequences throughout the geological record as far back as the Neoproterozoic, e.g. within beach-to-dune stratigraphy in Pleistocene limestones of the Perth Basin and in southeastern USA, and in tidal-flat sands of the Mesozoic Broome Sandstone of the Canning Basin. The bubble-sand structure is a significant geological tool for use in paleo-environmental and paleo-oceanographic reconstructions, and determination of the position of a paleo-water-table. Given the rarity of their preservation, these occurrences of bubble-sand structures are of geoheritage significance in their own right and, depending on age of sequence and how common they are in the region, they may be nationally significant or globally significant.

The Pilbara region of Western Australia, covering some 500 km × 500 km, provides a diversity of Archaean to Proterozoic igneous rocks in a relatively compact area that records a younging southward crustal history of igneous activity, sedimentation, early life, tectonics, and metamorphism from the Archaean (3.6–2.7 Ga) to Proterozoic (2.5–1.8 Ga). The igneous rocks are variable in age, types of rocks, and mode of occurrence and, throughout the Precambrian, record varying igneous rock activity that appear related to several age-related geological settings: to north, the Archaean Pilbara Craton consists of a granitoid-and-greenstone complex; in the central region, there are Proterozoic sequences of volcanic rock, volcaniclastic rock, ironstone, chert, dolomite, shale, and intrusive dolerite sills and cross-cutting dolerite dykes; to the south, there are Proterozoic shale, dolomite, and chert with isolated granitic batholiths. Igneous activity begins in the Archaean with mafic and ultramafic volcanism alternating with sedimentation, and then granitoid cratonisation. This was followed by Proterozoic volcanic crustal accretion with mafic volcanic and volcaniclastic rocks, and by dolerite and gabbro sill and dyke intrusions, ending with isolated granite batholithic intrusions. Igneous rocks in the Pilbara region are diverse: komatiite; mafic volcanic/volcaniclastic rocks; basalt; tuff/volcanic breccia/accretionary lapilli; dolerite, gabbro, leucogabbro, pegmatitic gabbro, granite, and adamellite; xenolithic dolerite/gabbro; andesite, dacite, rhyodacite, rhyolite; granitoids: adamellite, monzogranite, syenogranite, granodiorite, tonalite, granite; granophyre; felsic dykes; and felsic porphyry. They are expressed as granitoid batholiths, komatiite and basalt sheets/lenses, mafic volcanic/volcaniclastic rocks in sheets, sills of dolerite, gabbro, ultramafic rocks, and diorite, dykes of dolerite, gabbro, and felsic rocks, structurally-oriented dolerite dyke swarms, tuff/volcanic breccia/accretionary lapilli in sheets/lenses, sheets of dacite, rhyodacite, rhyolite, and andesite, gabbroic plugs, apophyses, and a variety of host-rock to xenolith relationships. Today, the Pilbara region is arid, hence outcrop is excellent and many of these geological features are well exposed. The diversity of Archaean to Proterozoic igneous rocks in a relatively compact and well-exposed area and qualifies it as a globally unique potential Precambrian igneous-rock geopark.

In the growing field of Geoheritage, Geoconservation, Geo-education and Geotourism, there is a need to manage sites of geoheritage significance. While there is some great geology in nature available to appreciate for scenic value, education, tourism and research, many locations need to be protected from people and commercialism (e.g. the Iridium layer at the K/T boundary in Gubbio, Italy, the Ediacaran fauna in South Australia, the Burgess Shale in Canada or the zircon crystals at Jack Hills, among many others), and some locations need hazard management to protect people (e.g. continuously collapsing cliffs that have potential to be hazardous via rock falls, or slippery slopes, or high cliffs that are treacherous, or ‘king waves’ on rocky shores). The concept of the ‘8Gs’ is intended as a policy-style guidance that logically and progressively links Geology and Geoheritage through a series of steps to Geo-education and Geotourism. There is a logical progression from Geology the Science, through to Geoheritage and the identification of sites of geoheritage significance, to the establishment of Geosites/Geoparks, Geoconservation, leading to Geomanagement, Geo-education and Geotourism. Geomanagement needs to be undertaken prior to the use of sites for Geo-education and Geotourism. In relation to Geomanagement, sites need to be investigated for safety issues, and for the protection of their geological features. Geodiversity, the eighth ‘G’, is outside the progression but plays an important part in underpinning biodiversity. There is also a need to address and manage geodiversity in a given region or specific site to help understand and manage biodiversity.