Geological control of physiography in Southeast Queensland: A multi-scale analysis using GIS

The study reported here, constitutes a full review of the major geological events that have influenced the morphological development of the southeast Queensland region. Most importantly, it provides evidence that the region’s physiography continues to be geologically ‘active’ and although earthquakes are presently few and of low magnitude, many past events and tectonic regimes continue to be strongly influential over drainage, morphology and topography. Southeast Queensland is typified by highland terrain of metasedimentary and igneous rocks that are parallel and close to younger, lowland coastal terrain. The region is currently situated in a passive margin tectonic setting that is now under compressive stress, although in the past, the region was subject to alternating extensional and compressive regimes. As part of the investigation, the effects of many past geological events upon landscape morphology have been assessed at multiple scales using features such as the location and orientation of drainage channels, topography, faults, fractures, scarps, cleavage, volcanic centres and deposits, and recent earthquake activity. A number of hypotheses for local geological evolution are proposed and discussed. This study has also utilised a geographic information system (GIS) approach that successfully amalgamates the various types and scales of datasets used. A new method of stream ordination has been developed and is used to compare the orientation of channels of similar orders with rock fabric, in a topologically controlled approach that other ordering systems are unable to achieve. Stream pattern analysis has been performed and the results provide evidence that many drainage systems in southeast Queensland are controlled by known geological structures and by past geological events. The results conclude that drainage at a fine scale is controlled by cleavage, joints and faults, and at a broader scale, large river valleys, such as those of the Brisbane River and North Pine River, closely follow the location of faults. These rivers appear to have become entrenched by differential weathering along these planes of weakness. Significantly, stream pattern analysis has also identified some ‘anomalous’ drainage that suggests the orientations of these watercourses are geologically controlled, but by unknown causes. To the north of Brisbane, a ‘coastal drainage divide’ has been recognized and is described here. The divide crosses several lithological units of different age, continues parallel to the coast and prevents drainage from the highlands flowing directly to the coast for its entire length. Diversion of low order streams away from the divide may be evidence that a more recent process may be the driving force. Although there is no conclusive evidence for this at present, it is postulated that the divide may have been generated by uplift or doming associated with mid-Cenozoic volcanism or a blind thrust at depth. Also north of Brisbane, on the D’Aguilar Range, an elevated valley (the ‘Kilcoy Gap’) has been identified that may have once drained towards the coast and now displays reversed drainage that may have resulted from uplift along the coastal drainage divide and of the D’Aguilar blocks. An assessment of the distribution and intensity of recent earthquakes in the region indicates that activity may be associated with ancient faults. However, recent movement on these faults during these events would have been unlikely, given that earthquakes in the region are characteristically of low magnitude. There is, however, evidence that compressive stress is building and being released periodically and ancient faults may be a likely place for this stress to be released. The relationship between ancient fault systems and the Tweed Shield Volcano has also been discussed and it is suggested here that the volcanic activity was associated with renewed faulting on the Great Moreton Fault System during the Cenozoic. The geomorphology and drainage patterns of southeast Queensland have been compared with expected morphological characteristics found at passive and other tectonic settings, both in Australia and globally. Of note are the comparisons with the East Brazilian Highlands, the Gulf of Mexico and the Blue Ridge Escarpment, for example. In conclusion, the results of the study clearly show that, although the region is described as a passive margin, its complex, past geological history and present compressive stress regime provide a more intricate and varied landscape than would be expected along typical passive continental margins. The literature review provides background to the subject and discusses previous work and methods, whilst the findings are presented in three peer-reviewed, published papers. The methods, hypotheses, suggestions and evidence are discussed at length in the final chapter.

Surveying the Wide Bay Burnett : changing lifestyles and the implications for regional transport planning

Significant lifestyle and demographic changes in Queensland are beginning to alter the landscape of regional transport planning. In 2006, Queensland Transport undertook a study to understand the implications of these changes on the transport planning task in regional Queensland. The study focused on the current travel characteristics of three Local Government Areas in the Wide Bay Burnett Region. Hervey Bay City represented the ‘sea change’ phenomenon; Wondai Shire represented the growing ‘tree change’ lifestyle; and Monto Shire represented communities which were either experiencing limited change or a decrease in population. The results of this research will be used to inform long term integrated regional transport planning in the region.

Understanding past climate variation and environmental change for the future of an iconic landscape – K'gari Fraser Island, Queensland, Australia

The unique combination of landscapes and processes that are present and operate on Fraser Island (K'gari) create a dynamic setting that is capable of recording past environmental events, climate variations and former landscapes. Likewise, its geographic position makes Fraser Island sensitive to those events and processes. Based on optically stimulated luminescence dating, the records archived within the world's largest sand island span a period that has the potential to exceed 750 ka and contain specific records that are of extremely high resolution over the past 40,000 years. This is due to the geographic position of Fraser Island, which lies in the coastal subtropical region of Queensland Australia. Fraser Island is exposed to the open ocean currents of the Coral Sea on the east coast and the waters of Hervey Bay on its western margin and is positioned to receive moisture from the Indo-Australian monsoon, southeast trade winds and experiences occasional tropical and ex-tropical cyclones. We review literature that presents the current level of understanding of sea level change, ecological variation and environmental change on Fraser Island. The previous works illustrate the importance of Fraser Island and may link processes, environments and climates on Fraser Island with global records.

Relationships between major ions in coal seam gas groundwaters: Examples from the Surat and Clarence-Moreton basins

Using a combination of multivariate statistical techniques and the graphical assessment of major ion ratios, the influences on hydrochemical variability of coal seam gas (or coal bed methane) groundwaters from several sites in the Surat and Clarence-Moreton basins in Queensland, Australia, were investigated. Several characteristic relationships between major ions were observed: 1) strong positive linear correlation between the Na/Cl and alkalinity/Cl ratios; 2) an exponentially decaying trend between the Na/Cl and Na/alkalinity ratios; 3) inverse linear relationships between increasing chloride concentrations and decreasing pH for high salinity groundwaters, and; 4) high residual alkalinity for lower salinity waters, and an inverse relationship between decreasing residual alkalinity and increasing chloride concentrations for more saline waters. The interpretation of the hydrochemical data provides invaluable insights into the hydrochemical evolution of coal seam gas (CSG) groundwaters that considers both the source of major ions in coals and the influence of microbial activity. Elevated chloride and sodium concentrations in more saline groundwaters appear to be influenced by organic-bound chlorine held in the coal matrix; a sodium and chloride ion source that has largely been neglected in previous CSG groundwater studies. However, contrastingly high concentrations of bicarbonate in low salinity waters could not be explained, and are possibly associated with a number of different factors such as coal degradation, methanogenic processes, the evolution of high-bicarbonate NaHCO3 water types earlier on in the evolutionary pathway, and variability in gas reservoir characteristics. Using recently published data for CSG groundwaters in different basins, the characteristic major ion relationships identified for new data presented in this study were also observed in other CSG groundwaters from Australia, as well as for those in the Illinois Basin in the USA. This observation suggests that where coal maceral content and the dominant methanogenic pathway are similar, and where organic-bound chlorine is relatively abundant, distinct hydrochemical responses may be observed. Comparisons with published data of other NaHCO3 water types in non-CSG environments suggest that these characteristic major ion relationships described here can: i) serve as an indicator of potential CSG groundwaters in certain coal-bearing aquifers that contain methane; and ii) help in the development of strategic sampling programmes for CSG exploration and to monitor potential impacts of CSG activities on groundwater resources.