From 1 - 10 / 140
  • Along the Aceh-Andaman subduction zone, there was no historical precedent for an event the size of the 2004 Sumatra-Andaman tsunami; therefore, neither the countries affected by the tsunami nor their neighbours were adequately prepared for the disaster. By studying the geological signatures of past tsunamis, the record may be extended by thousands of years, leading to a better understanding of tsunami frequency and magnitude. Sedimentary evidence for the 2004 Sumatra-Andaman tsunami and three predecessor great Holocene tsunamis is preserved on a beach ridge plain on Phra Thong Island, Thailand. Optically stimulated luminescence ages were obtained from tsunami-laid sediment sheets and surrounding morphostratigraphic units. Single-grain results from the 2004 sediment sheet show sizable proportions of near-zero grains, suggesting that the majority of sediment was well-bleached prior to tsunami entrainment or that the sediment was bleached during transport. However, a minimum-age model needed to be applied in order to obtain a near-zero luminescence age for the 2004 tsunami deposit as residual ages were found in a small population of grains. This demonstrates the importance of considering partial bleaching in water-transported sediments. The OSL results from the predecessor tsunami deposits and underlying tidal flat sands show good agreement with paired radiocarbon ages and constrain the average recurrence of large late Holocene tsunami on the western Thai coast to between 500 to 1000 years. This is the first large-scale application of luminescence dating to gain recurrence estimates for large Indian Ocean tsunami. These results increase confidence in the use of OSL to date tsunami-laid sediments, providing an additional tool to tsunami geologists when material for radiocarbon dating is unavailable. Through an understanding of the frequency of past tsunami, OSL dating of tsunami deposits can improve our understanding of tsunami hazard and provide a means of assessing fu

  • The ratio of benthic silicate (SiO4 or DSi1) vs carbon dioxide (CO2) fluxes at 299/341 (87%) sites in 10 Australian estuaries was 0.15 to 0.19 (r2=0.8), indicating diatoms 2,3 as the major type of organic material (OM) being degraded in the sediments . Diatoms contributed 33% of the degradable OM at the remaining 42 (13%) sites. Diatomaceous phytoplankton was thus central to nutrient cycling in these estuaries. Dam-induced DSi depletion in coastal waters, a cause of toxic non-silicious algal blooms is now a global problem1. Our investigation indicated that DSi has another and potentially important global role in nutrient cycling in coastal waterways, also prompting a new DSi-dependent nutrient cycling model. The Si-opal inclusion (frustule) in living diatoms confers a density that causes rapid settling to the sediments4 where denitrification recycles N2 to an atmospheric sink, in this way lowering internal N cycling and preventing eutrophication5. Also, DSi is recycled quantitatively to the water column, participating in repeated cycles of diatom productivity. The silicate-diatom-sediment nexus is thus sustained and the N-loss processes of denitrification and burial are sustained.

  • Australia has developed as a maritime nation, from the reliance on coastal seas for transport and trade to the present day where most of the nation's population, industry, tourism and recreation are located along its coasts. In `A Geology of Australia', we discuss how coastal geological features and processes have strongly influenced the pattern of post-colonial settlement and development of Australia, and how our experience of the coast varies radically depending on our location on the continental margin. Examples are provided of the influence of coastal geology on society as well as the impacts people have had on coastal systems.

  • Freshwater coastal aquifers provide an important resource for irrigated agriculture, human consumption and the natural environment. Approximately 18 million people live within 50 km of the coast in Australia, and many coastal communities are reliant on groundwater. These coastal aquifers are vulnerable to seawater intrusion (SWI) - the landward encroachment of seawater - due to their close proximity to the ocean. To assess the threat of SWI in Australia, a comprehensive literature review was undertaken with input from state/territory agencies. The literature review, in combination with contributions from stakeholders, identified sites within each of the states and the Northern Territory where SWI had been reported or where it was considered to be a serious threat. International Association of Hydrogeologists 2013 Congress poster

  • The coastal zone is arguably the most difficult geographical region to capture as data because of its dynamic nature. Yet, coastal geomorphology is fundamental data required in studies of the potential impacts of climate change. Anthropogenic and natural structural features are commonly mapped individually, with their inherent specific purposes and constraints, and subsequently overlain to provide map products. This coastal geomorphic mapping project centered on a major coastal metropolitan area between Lake Illawarra and Newcastle, NSW, has in contrast classified both anthropogenic and natural geomorphological features within the one dataset to improve inundation modelling. Desktop mapping was undertaken using the Australian National Coastal Geomorphic (Polygon) Classification being developed by Geoscience Australia and supported by the Department of Climate Change. Polygons were identified from 50cm and 1m aerial imagery. These data were utilized in parallel with previous maps including for example 1:25K Quaternary surface geology, acid sulphate soil risk maps as well as 1:100K bedrock geology polygon maps. Polygons were created to capture data from the inner shelf/subtidal zone to the 10 m contour and include fluvial environments because of the probability of marine inundation of freshwater zones. Field validation was done as each desktop mapping section was near completion. This map has innovatively incorporated anthropogenic structures as geomorphological features because we are concerned with the present and future geomorphic function rather than the past. Upon completion it will form part of the National Coastal Geomorphic Map of Australia, also being developed by Geoscience Australia and utilized in conjunction with Smartline.

  • No abstract available

  • A comprehensive black and white teachers' guide reviews the history and development of the United Nation's Convention on the Law of the Sea and its application to Australian marine jurisdiction. Case studies on the North West Shelf, Antarctica and Orange Roughy are included. 108 page booklet with student activities and suggested answers. Suitable for secondary geography and science students Years 8-12.

  • This record contains the raw Ground Penetrating Radar (GPR) data and scanned field notes collected on fieldwork at Old Bar and Boomerang Beaches, NSW for the Bushfire and Natural Hazards CRC Project, Resilience to Clustered Disaster Events on the Coast - Storm Surge. The data was collected from 3 - 5 March 2015 using a MALA ProEx GPR system with 250 MHz shielded and 100 MHz unshielded antennaes. The aim of the field work was to identify and define a minimum thickness for the beach and dune systems, and where possible depth to any identifiable competent substrate (e.g. bedrock) or pre-Holocene surface which may influence the erosion potential of incident wave energy. Surface elevation data was co-acquired and used to topographically correct the GPR profiles.

  • The Australian Coastal Sediment Compartments Web Service provide a hierarchical spatial classification relevant to the assessment of sediment movement in the Australian coastal zone, and represent a tool to assist coastal planning and management. Additional spatial data layers produced during the development of the compartments are provided for reference.

  • Australia's near-pristine estuaries are some of our most valuable natural assets, with many natural and cultural heritage values. They are important as undisturbed habitat for native plants and animals, for biodiversity conservation, as Indigenous lands and for tourism. They also support near-shore fisheries. In addition, by studying near-pristine estuaries, scientists can learn more about the way humans have changed natural systems. This information then feeds into natural resource management because it constitutes benchmark or baseline information against which similar information from more modified estuaries can be compared.