b'AEGC 2023Short abstractsClimatic Optimum (MMCO), which saw the onset of isolatedupper crust, often referred to as the Tasman Line. The South carbonate build-ups and carbonate platform development, (2) aAustralian part of this continental margin has been interpreted, rise in sea level amplitude and decreasing frequency during thebased on sparse extrapolated constraints, to have sat in various Mid Pleistocene Transition (MPT) between ca.0.8-0.6Ma and thegeodynamic settings associated with a Cambrian subduction associated change in regional climate from wet to dry, and (3)system. We use newly acquired multi-disciplinary datasets glacial-interglacial variability throughout the Pleistocene untiland the results of the MinEx CRC Delamerian National Drilling present day. North and South Scott Reefs are isolated carbonateInitiative programme to elucidate the architecture of this reefs separated by an inter-reef channel on the NWS thathidden Cambrian margin, and reveal unrecognised potential for evolved from a carbonate platform - part of the largest barriera spectrum of mineral systems.reef system in the Neogene. However, the timings of coral reef turn on and off are insufficiently understood with respect toWhilst it has been accepted for a number of years that the global climatic changes in this region. Availability of 3D seismicStavely Zone in western Victoria represents a volcanic arc in the data provides a unique opportunity to investigate the evolutionmid-Cambrian, continent-ward belts to the west (beneath the of these reefs using seismic stratigraphy (SS) and seismicMurray Basin), have had uncertain affinities. With the results geomorphology. SS reveals that despite rapid accommodationof recent drilling, we show that both regional, and highly rate changes as a result of global (e.g., climate, eustasy) andpartitioned back-arc extension were present in the period 514-regional (e.g., tectonics) forcing parameters, the unique500 Ma, and speculate that inherited structure in pre-Cambrian oceanographic setting, antecedent topography and rapidbasement rocks are responsible for the variation in deformation vertical reef accretion played a key role in their survival. Thestyles present in drill core.Indonesian throughflow, Leeuwin current, tides, swells and wind regimes were likely major influences on the NWS climate, whilst the inter-reef channel probably bypassed terrigenous sedimentUnveiling the seismic image beneath volcanics in the influx away from the reefs basinward via canyons, avoidingBass Basin.periods of inundation during wet climates in the Pliocene. Shiping Wu , Xiang Li , Jianfeng Yao , Jon Cockerand James 1 1 1 2Martindale2Shear-Wave seismic reflection case study for use in the1 CGG provision of shallow seismic profiles for geotechnical2 Beach Energy Ltdinvestigations. Volcanic and intrusive igneous rocks are common throughout Taylor Willick and Simon Williams the offshore Bass Basin, Southeast Australia, due to multiple episodes of magmatism. These igneous bodies have very GBG Group complex internal structures that cause distorted seismic images and poor illumination beneath them. This paper demonstrates Shear-Wave seismic reflection was utilised to delineate thean application of Time-Lag Full Wave-form Inversion (TLFWI), bedrock within a palaeo valley system along with otherand an integrated de-multiple workflow to greatly improve the reflectors within the sediment profile that may be pertinentseismic image beneath volcanic bodies.to a road viaduct construction. The road viaduct construction had planned to socket piles in the bedrock. However,The legacy seismic data is from a narrow-azimuth short shallower sediment lenses of adequate stiffness within thestreamer (3000 m) dataset and results in a poor image at the sediment profile may have utility for friction pile design andreservoir level due to two primary reasons: 1) inaccurate velocity provide a design and construction cost advantage. Priormodel within and beneath the complex volcanics; and 2) to commencement of the primary field campaign, a trialstrong residual surface and inter-bed multiples generated by comparison between compressional-wave seismic reflectionthe volcanic anomalies and shallow seabed that dominate the utilising explosives and shear-wave reflection utilising shear- weaker primary signals.wave vibration sources was made. Based on the trial testTo improve the model accuracy, high-frequency TLFWI up to results and subsequent refinement of collection parameters30 Hz using both diving waves and reflection energy is applied the primary campaign was carried out using the Shear-waveto obtain a high-resolution velocity model inside and beneath reflection source. The method was successful in resolving thethe shallow volcanic bodies. To resolve the strong multiple general bedrock trend in the palaeo channel system alongissue, a comprehensive de-multiple workflow, including with lenses within the sediment profile and distinct variationsshallow water de-multiple, iterative 3D SRME and inter-bed in sediment Shear-wave velocities. The approximately 1800de-multiple, combined with 3D curvelet domain subtraction, m of total survey profiles increased the confidence in theis employed.shallow subsurface geological model and provided improved information on the geotechnical parameters. Finally, Least-Squares Q Migration is applied on the significantly improved pre-processed data and velocity to achieve: 1) well-defined volcanic bodies that enable the unveiling of the The Delamerian NDI: Linking South and easternunderlying events and hence suitability for interpretation; 2) Australia. an excellent synthetic well-tie and overall small depth mis-ties; and 3) a seismic volume with improved confidence for attribute Tom Wise inversion. The uplift in imaging allowed confident mapping of Geological Survey of South Australia a previously unidentified upthrown fault-bound closure that could lead to further development of the Yolla field, which is The western Murray Basin obscures the interpreted transitionimportant to meet the raising demand for natural gas on the between Proterozoic and Phanerozoic rocks of Australia in theEast Coast of Australia.153 PREVIEW FEBRUARY 2023'