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Landslides in the Sydney Basin - Geoscience Australia

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Seismic Hazard <strong>in</strong> <strong>Sydney</strong>Proceed<strong>in</strong>gs of <strong>the</strong> one day workshopapparently contradicted by untilted Miocene magnetisation at Lapstone (Bishop et al. 1979) but itdoes provide a plausible explanation for <strong>the</strong> problematic Rickabys Creek Gravel at Glenbrook (cf.Pickett & Bishop 1992).Given <strong>the</strong> great antiquity of much of <strong>the</strong> landscape <strong>in</strong> eastern <strong>Australia</strong>, <strong>the</strong> lack of evidence fornotable tectonic events <strong>in</strong> <strong>the</strong> latest Cretaceous to latest Palaeogene and recent evidence of LateNeogene deformation and uplift <strong>in</strong> sou<strong>the</strong>astern <strong>Australia</strong> (Sandiford 2003), it is important to reevaluate<strong>the</strong> role of reactivation and neotectonic activity on structures such as <strong>the</strong> Lake GeorgeFault, Mulwaree Fault and Lapstone Structural Complex. The present-day seismicity of sou<strong>the</strong>astern<strong>Australia</strong> <strong>in</strong>dicates that thrust fault<strong>in</strong>g is active and <strong>the</strong>refore west-dipp<strong>in</strong>g structures with potentialevidence for neotectonic activity should be carefully exam<strong>in</strong>ed. More cross sections drawn to depth<strong>in</strong>corporat<strong>in</strong>g seismic and borehole data are needed to determ<strong>in</strong>e if <strong>the</strong>se structural geometries areviable.ACKNOWLEDGEMENTSDr Dan Clark is thanked for organis<strong>in</strong>g <strong>the</strong> symposium on <strong>the</strong> Lapstone Structural Complex. DrDavid Branagan k<strong>in</strong>dly commented on a draft of this manuscript. Dr Hosse<strong>in</strong> Memarian is thankedfor many discussions on <strong>Sydney</strong> Bas<strong>in</strong> structure. I am most grateful to <strong>the</strong> late Professor PeterConey for show<strong>in</strong>g me <strong>the</strong> Colorado Plateau and it’s monocl<strong>in</strong>es <strong>in</strong> 1993.REFERENCESAbell, R. S., 1991. Geology of <strong>the</strong> Canberra 1:100 000 Sheet area, New South Wales and <strong>Australia</strong>nCapital Territory. Bureau of M<strong>in</strong>eral Resources, Geology & Geophysics, Bullet<strong>in</strong>, 233,116pp.Bishop, P., Hunt P. and Schmidt, P. W., 1982. Limits to <strong>the</strong> age of <strong>the</strong> Lapstone Monocl<strong>in</strong>e,N.S.W. a palaeomagnetic study. Journal of <strong>the</strong> Geological Society of <strong>Australia</strong>, 29, 319–326.Branagan, D. F. and Pedram, H., 1990. The Lapstone Structural Complex, New South Wales.<strong>Australia</strong>n Journal of Earth Sciences, 37, 23–36.Branagan, D. F. and Pedram, H., 1997. Eng<strong>in</strong>eer<strong>in</strong>g geology of a sandstone escarpment: <strong>the</strong> BlueMounta<strong>in</strong>s. <strong>Sydney</strong> Bas<strong>in</strong> NSW. In: McNally G. (Ed.) Collected Case Studies <strong>in</strong> Eng<strong>in</strong>eer<strong>in</strong>gGeology, Hydrogeology and Environmental Geology. Third Series. Environmental,Eng<strong>in</strong>eer<strong>in</strong>g and Hydrogeology Specialist Group, Geological Society of <strong>Australia</strong> andConference Publications, pp. 38–52.Brown, A. and Gibson, G., 2004. A multi-tiered earthquake hazard model for <strong>Australia</strong>.Tectonophysics, 390, 25–43.Bump, A. P. and Davis, G. H., 2003. Late Cretaceous–early Tertiary Laramide deformation of <strong>the</strong>nor<strong>the</strong>rn Colorado Plateau, Utah and Colorado. Journal of Structural Geology, 25, 421–440.Clarke, N. R. and Jones, D. C., (Eds.), 1991. Penrith 1:100 000 Geological Sheet 9030. New SouthWales Geological Survey, <strong>Sydney</strong>.Cooper, G. T., 1992. Early Carboniferous back-arc deformation <strong>in</strong> <strong>the</strong> Lachlan Fold Belt,Shoalhaven River–Ettrema Creek area, NSW. <strong>Australia</strong>n Journal of Earth Sciences, 39, 529–537.Fergusson, C. L., 1998. Thick-sk<strong>in</strong>ned fold<strong>in</strong>g <strong>in</strong> <strong>the</strong> eastern Lachlan Fold Belt: an example from <strong>the</strong>Shoalhaven River Gorge, New South Wales. <strong>Australia</strong>n Journal of Earth Sciences, 45, 677–686.Fergusson, C. L. and Frikken, P., 2003. Diapirism and structural thicken<strong>in</strong>g <strong>in</strong> an Early Palaeozoicsubduction complex, sou<strong>the</strong>astern New South Wales, <strong>Australia</strong>. Journal of StructuralGeology, 25, 43–58.17

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