Geological Control of Physiography in Southeast Queensland
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Geological control of physiography in southeast Queensland: a multi-scale analysis using GIS Jane Helen Hodgkinson Bachelor of Science (Hons), Geology (Birkbeck University of London, UK) School of Natural Resource Sciences A thesis submitted for the degree of Doctor of Philosophy Queensland University of Technology 2009 ii STATEMENT OF ORIGINAL AUTHORSHIP The work contained in this thesis has not been previously submitted for a degree or diploma at any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made. Signed………………………………… Jane Helen Hodgkinson Date…………………………… iii iv ABSTRACT 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 v 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. vi Keywords Geomorphology, GIS, Drainage patterns, Stream-ordering, southeast Queensland, Passive margin, Earthquake distribution vii LIST OF PUBLICATIONS REFEREED INTERNATIONAL JOURNAL PAPERS PAPER 1 Title: The influence of geological fabric and scale on drainage pattern analysis in a catchment of metamorphic terrain: Laceys Creek, southeast Queensland, Australia Authors: Jane Helen Hodgkinson, Stephen McLoughlin, Malcolm Cox Status: Published November 2006 (available on-line from July 2006) Journal: Geomorphology, 81 394-407 PAPER 3 Title: Drainage patterns in southeast Queensland: the key to concealed geological structures? Authors: Jane Helen Hodgkinson, Stephen McLoughlin, Malcolm Cox Status: Published December 2007 Journal: Australian Journal of Earth Sciences, 54 1137-1150 REFEREED CONFERENCE PAPER PAPER 2 Title: The correlation between physiography and neotectonism in southeast Queensland Authors: Jane Helen Hodgkinson. Stephen McLoughlin, Malcolm Cox Status: Reviewed for DEST purposes, published in conference proceedings, presented with poster (Appendix 1) Conference: Australian Earthquake Engineering Society Conference, Canberra, ACT November 2006 viii ACKNOWLEDGEMENTS I wish to acknowledge the support and encouragement provided by my principle supervisor, Dr Stephen McLoughlin who gave invaluable advice and comments, who gave his time generously and whose ability and standards I will always strive to emulate. My associate supervisor, Associate Professor Malcolm Cox also provided constructive support, held many useful discussions, and contributed his valuable time for the review of manuscripts, for which I am very grateful. I am indebted to Dr Andrew Hammond for his help, support and valuable advice, and for our countless beneficial talks and debates. I am grateful to Dr Micaela Preda for sharing her wealth of GIS knowledge with me and for our constructive discussions with regard to local geology and geomorphological analysis. I also acknowledge the helpful and educational discussions and field trips with Mr Bill Ward whose interest in the subject of geomorphology is valuable and encouraging. Further, I wish to express my gratitude to Mr Nate Peterson who provided valuable assistance with GIS methodology. This research project would not have been possible without the datasets provided by various sources. Special thanks go to Dr Dion Weatherly and Mr Col Lynam at the Earth Systems Science Computational Centre (ESSCC), University of Queensland, for their enormous encouragement with my project, for their collaborative discussions and for providing their valuable earthquake database. Thanks also goes to Geoscience Australia for further earthquake data, and to Pine Rivers Shire Council and the Geological Survey of Queensland at the Department of Mines and Energy (Queensland Government) for providing geological, topographical and drainage data, which were required for GIS analysis. Datasets were also obtained from USGS/NASA via their on-line service, without which, the first paper could not have been written. I would like to thank all the staff and students in the School of Natural Resource Sciences at QUT, whose help and encouragement have been a great benefit to me in the course of this study. I also thank the staff at the School of Earth Sciences, Birkbeck University of London, among other things, for inspiring me in the ix wonderful subject of geology. I also thank all my friends and family both in Australia and the UK, who believed I could do this. I especially thank Jean and David Hodgkinson, Madonna O’Brien, Ben Henderson, Jennifer Baker, Caroline Cole, Jeanette Fleming, John Hodge and everyone from the ‘Whitton School Class of 1982’, whose humour and friendship has been invaluable. A particularly special thank you goes to Jonathan Hodgkinson, my husband, friend, field assistant, fellow student and room-mate at QUT, whose help and encouragement is beyond measure. I also express my gratitude to my late parents to whom I dedicate