1. Blevin et al.:Hydrocarbon prospectivity of the Bight Basin - petroleum systems analysis in a frontier basin 2. Boreham et al : Geochemical Comparisons Between Asphaltites on the Southern Australian Margin and Cretaceous Source Rock Analogues 3. Brown et al: Anomalous Tectonic Subsidence of the Southern Australian Passive Margin: Response to Cretaceous Dynamic Topography or Differential Lithospheric Stretching? 4. Krassay and Totterdell : Seismic stratigraphy of a large, Cretaceous shelf-margin delta complex, offshore southern Australia 5. Ruble et al : Geochemistry and Charge History of a Palaeo-Oil Column: Jerboa-1, Eyre Sub-Basin, Great Australian Bight 6. Struckmeyer et al : Character, Maturity and Distribution of Potential Cretaceous Oil Source Rocks in the Ceduna Sub-Basin, Bight Basin, Great Australian Bight 7. Struckmeyer et al: The role of shale deformation and growth faulting in the Late Cretaceous evolution of the Bight Basin, offshore southern Australia 8. Totterdell et al : A new sequence framework for the Great Australian Bight: starting with a clean slate 9. Totterdell and Bradshaw : The structural framework and tectonic evolution of the Bight Basin 10. Totterdell and Krassay : The role of shale deformation and growth faulting in the Late Cretaceous evolution of the Bight Basin, offshore southern Australia

Palynological studies of Triassic-Jurassic well sections in the Offshore North Perth Basin have helped to reveal a more complicated geological history than previously recognised. This work is part of a major Geoscience Australia project studying the geological history and petroleum prospectivity of the basin. Seismic and well log interpretations have been combined with the sedimentological data to develop a high resolution sequence stratigraphic framework. This work is heavily reliant on the palynological data to provide the necessary age control, palaeoenvironmental interpretations and well correlations. Abstract continues (no space in field).

The Early Cretaceous Gage Sandstone and South Perth Shale formations are a prospective reservoir-seal pair in the Vlaming Sub-basin. Plays include post-breakup pinch-outs in the Gage Sandstone with the South Perth Shale forming top seal. The Gage reservoir has porosities of 18-25% and permeabilities of 1-1340 mD. It was deposited in palaeotopographic lows of the Valanginian breakup unconformity and is the lowstand component of the thick deltaic South Perth (SP) Supersequence. To characterise the reservoir-seal pair, a detailed sequence stratigraphic analysis was conducted by integrating 2D seismic interpretation, well log analysis and new biostratigraphic data. Palaeogeographic reconstructions for the SP Supersequence were derived from mapping higher-order prograding packages and establishing changes in sea level and sediment supply. Higher resolution Gage reservoir reconstructions were based on seismic facies mapping. The Gage reservoir forms part of a sand-rich submarine fan system similar to model proposed by Richards et al (1998). It ranges from canyon confined inner fan deposits to middle fan deposits on a basin plain. Directions of sediment supply are complex, with major sediment contributions from a northern and southern canyon adjacent to the Badaminna Fault Zone. The characteristics of the SP Supersequence differ markedly between the northern and southern parts of the sub-basin due to variations in palaeotopography and sediment supply. Palaeogeographic reconstructions reveal a series of regressions and transgressions leading to infilling of the palaeo-depression. Palaeogeographic reconstructions for the SP Supersequence portray a complex early post-rift depositional history in the central Vlaming Sub-basin. The developed approach is applicable for detailed studies of other sedimentary basins. APPEA

The Darling Basin is a Late Silurian to Early Carboniferous feature occupying approximately 100 000 km2 of western New South Wales. In the area of the Pondie Range Trough, near the town of Wilcannia, it comprises up to 12 000 m of sediments, interpreted to have been deposited as syn-rift, thermal sag, and foreland basin phases of basin development, overlain by a veneer of Murray Basin and underlying infrabasin sediments.

As interpretations of sequence stratigraphy are published in increasing numbers in the petroleum exploration literature, the potential for confusion also increases because there are no rules for the classification or naming of the identified sequences. At present it is difficult to apply databases and geographic information systems to sequence stratigraphy, particularly when organisations with different outlooks and approaches attempt to collaborate and merge their databases. Despite sequence stratigraphic concepts having been in the literature for over two decades, no scheme for standardisation has achieved consensus in the geoscientific community, either within Australia or internationally. Three areas in particular need to be agreed on: (1) how sequence units should be defined; (2) the hierarchy of those units, and on what basis; and (3) a standard scheme for naming units. The two basic ways of subdividing a succession into sequence units, the Vail-Exxon and Galloway methods, both rely on the enclosing boundaries being defined first. Various hierarchies of units have been proposed, in which there is often a clear desire to link the scale of sequence units to phases of geological evolution or stratal boundaries of different orders. In addition, most workers use informal names, but formal names are becoming more common. Consequently, it is essential that workable national guidelines be developed to ensure that communication and computer compatibility are not impeded.

The Perth Basin formed as part of an obliquely-oriented extensional rift system on Australia's southwestern margin during the Paleozoic to Mesozoic breakup of eastern Gondwana. The Houtman Sub-basin is situated in the offshore portion of the northern Perth Basin, located about 200 km northwest of Perth. It is an elongate, northwest-southeast trending depocentre containing up to 14 km of Early Triassic to Late Jurassic sedimentary strata. A detailed sequence stratigraphic study has been undertaken on the three wells in the Houtman Sub-basin: Gun Island 1, Houtman 1 and Charon 1. The purpose of this study was to investigate facies variations between the wells to gain a better understanding of potential source, reservoir and seal distribution and to assist regional palaeogeographic reconstructions of the Perth Basin. The study focussed on the Early-Late Jurassic succession comprising the Cattamarra Coal Measures, Cadda Formation and Yarragadee Formation. Wireline log character, cuttings, sidewall core and conventional core lithologies and palynological data were used to identify facies and paleoenvironments. Palynology for all wells has been reviewed, including new data collected by Geoscience Australia for Gun Island 1 and Charon 1. Facies stacking patterns were used to define systems tracts and subsequently ten third-order depositional sequences. Collectively these sequences define a larger scale, second-order (supersequence) transgressive-regressive cycle. The Cattamarra Sequence Set forms a regional transgression which culminates in an extensive marine maximum flooding event within the Cadda Sequence Set. These sequence sets are followed by the regressive highstand Yarragadee Sequence Set. The third-order sequences characterised in this study overprint this supersequence and control the local distribution of facies. The combined influence of these third- and second-order sequences on facies distribution has significant implications for the distribution of potential reservoirs and seals, particularly in the northern Houtman Sub-basin where well and seismic data are relatively sparse.

The conjugate margins of Wilkes Land, Antarctica, and the Great Australian Bight (GAB) are amongst the least understood continental margins. Break up along the GAB-Wilkes Land part of the Australian-Antarctic margin commenced at approximately 83 Ma. Using recent stratigraphic interpretations developed for the GAB, we have established a sequence stratigraphy for the Wilkes Land margin that will, for the first time, allow for a unified study of the conjugate margins. By reconstructing the two margins to their positions prior to break up we were able to identify comparable packages on the Wilkes Land margin to those recognised on the GAB margin. Excluding the glacial sediments on the Antarctic margin, the sedimentary sequence along the Wilkes Land margin is very thin compared to the GAB margin, which has substantially more syn- and post-rift sediments. Despite the differences in thickness, the syn-rift sedimentary package on the Wilkes Land margin exhibits a similar style of extensional faulting and seismic character to its GAB margin counterpart. In comparison, post-rift sequences on the Wilkes Land margin are markedly different in geometry and seismic character from those found on the GAB margin. Isopach mapping shows substantial differences in the thickness of the post-breakup sediments, suggesting different sediment sources for the two margins. The Late Cretaceous Hammerhead Supersequence provides much of the post-rift thickness for the GAB margin as a result of large sediment influx into the basin. This supersequence is characterised by a thick progradational succession and was deposited in fluvio-deltaic and marine environments. The equivalent succession on the Wilkes Land margin has a different seismic character. It is thinner and aggradational, suggesting a distal marine environment of deposition.

Geoscience Australia is currently conducting a study under the National CO2 Infrastructure Plan (NCIP) to assess suitability of the Vlaming Sub-basin for CO2 storage. It involves characterisation of the potential seal, the Early Cretaceous South Perth Shale (SPS), by integrating seismic and well log interpretation into a sequence stratigraphic framework. The SPS, conventionally described as a regional seal deposited during a post-rift thermal subsidence phase, consists of a series of prograding units deposited in a deltaic to shallow marine setting. Mapping of the SPS has revealed differences in the geometries of progradational sequences between the northern and southern areas, related to the type and distance to the sediment source as well as the seafloor morphology. In the northern area, deltaic progradation and aggradation occurred over a flat topography between the two uplifted blocks. The succession is composed of prograding sequences commonly exhibiting sigmoidal to oblique geometries, prograding from the north-east to south-west. In the southern area the topography is more complex due to the presence of several paleotopographic highs associated with pre-existing structures. These sequences are sigmoidal to oblique in cross section. They were deposited in fan shaped lobes, successively infilling paleotopographic lows. Direction of the progradation is from southwest to northeast. The thickness of the SPS varies from 200 m between topographic highs to 700 m in the lows. Sedimentary facies are interpreted to vary from sandy delta front to muddy slope and prodelta deposits. These findings will be used in a 3D geological model for assessing CO2 storage potential.

The well folio package contains the combined data of 23 offshore wells in the northern Perth Basin, including the first published synthesis of data from fourteen new field wildcat wells drilled in this part of the basin since the Cliff Head 1 discovery (2001). Completed as part of the Australian Government's Offshore Energy Security Program, the well folio package will improve the assessment of petroleum prospectivity in the offshore Perth Basin. The well folio package consists of 23 composite well log plots, six well to well correlations and a new chronostratigraphic sequence framework and includes Geoscience Australia's revised Offshore Perth Basin Biozonation and Stratigraphy 2011 Chart 38 (Jones et al., 2011a). The well folio package summarises key stratigraphic, biostratigraphic and geochemical data and sequence interpretations for wells in the offshore northern Perth Basin from the Beagle and Turtle Dove ridges, Houtman and central Abrolhos sub-basins and the Wittecarra Terrace. Composite well log plots at 1:5000 scale summarise, in graphic form, the main stratigraphic features and hydrocarbon occurrences. The composite well logs also graphically summarise results from 120 new palynological samples and 244 new Rock-Eval pyrolysis/Total Organic Carbon (TOC), 85 new Vitrinite Reflectance (VR), 14 new FAMM maturity and compiled Grains with Oil Inclusions (GOITM) measurements. Compilations of new and open-file biostratigraphic and geochemical data are also included in digital spreadsheet formats. Data from the 23 offshore wells show that the main sedimentary succession in the offshore northern Perth Basin is Permian to Late Jurassic in age: two wells intersected a sandstone section of Late Cambrian to Early Ordovician age. Reviewed open-file biostratigraphic data, new biostratigraphic data and interpretations from these samples have been used in conjunction with well logs and lithological interpretations of cuttings, cores and side wall cores to define a new chronostratigraphic sequence framework for this part of the basin. Sequences and major maximum flooding surfaces are correlated between wells to show the spatial and temporal distribution of these sequences through the offshore northern Perth Basin.

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