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 study focussed on the Early-Late Jurassic Cattamarra Coal Measures, Cadda Formation and Yarragadee Formation succession. 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. Facies stacking patterns were used to define systems tracts and subsequently ten third-order depositional sequences. At the second-order (supersequence) level, the Cattamarra Coal Measures record a transgression culminating in maximum flooding in the Cadda Formation followed by highstand aggradation and regression in the Yarragadee Formation. The third-order sequences characterised in this study overprint this supersequence and control the local distribution of facies. The relative dominance of a facies may be either enhanced or diminished depending upon its position within the larger second-order supersequence. For example, a number of transgressive systems tracts within the dominantly non-marine Yarragadee Formation and Cattamarra Coal Measures record multiple, dinocyst-bearing, minor marine incursions into the Houtman Sub-basin. These marine incursions are not evident in the Yarragadee Formation in Charon 1, indicating a lack of accommodation space or proximal sediment input in the north during the mid-late Jurassic. The combined influence of these third-order and second-order sequences on facies distribution has significant implications for the distribution of potential reservoirs and seals in the Houtman Sub-basin and for regional palaeogeographic reconstructions of the Perth Basin.

Two facies models are proposed to explain siliciclastic and carbonate depositional systems of 1800 Ma to 1640 Ma age in the Western Fold Belt of the Mt Isa Inlier. Both models record the response of depositional systems to storm-driven processes of sediment transport, dispersal and deposition on a shallow water shelf. The same suite of facies belts can also be identified in sedimentary successions of the Eastern Fold Belt. Slope driven processes of sediment transport and dispersal characterise turbidite and debrite deposits of the Soldiers Cap Group and Kuridala Formation and provide evidence for significantly greater water depths in this part of the basin from ~1685 Ma. Through the recognition of unconformity surfaces, their correlative conformities, maximum flooding and ravinement surfaces the facies belts are packaged into 7 supersequences for the interval 1800-1640 Ma. The new correlations are shown in an Event Chart that correlates linked depositional systems across the entire Mt Isa Inlier. Thick successions of turbidite and debrite deposits are restricted to the eastern parts of the Mt Isa Inlier and do not occur in the Western Fold Belt. A major phase of extension and rifting commenced at ~1740 Ma and by ~1690 Ma led to significant crustal thinning and increased rates of accommodation over an area east of the Selwyn Fault and Burke River Structural Belt. In the Mitakoodi and Selwyn Blocks the rapid transition from shallow water shelf depositional systems of the Prize Supersequence to significantly deeper water slope environments of the Gun Supersequence coincided with the development of a platform margin, the deposition of turbidite and debrite deposits in deep water on the continental slope and the intrusion of mafic sills and dykes. Turbidite and debrite depositional systems of the Soldiers Cap Group and Kuridala Formations are restricted to a lowstand wedge of siliciclastic facies deposited basinward of a platform margin. Basin geometries and sediment architectures associated with this extensional event and recorded in the Gun Supersequence (~1685 Ma to 1650 Ma) provide an explanation for the geographic separation and fluid evolution pathways responsible for the Mt Isa Type and Broken Hill Type Zn-Pb-Ag deposits.

No abstract available

No abstract available

Techtonostratigraphic synthesis - Compilation and analysis of Geoscience Australia's studies of basins along Australia's southern margin over the last 10 years.

Poorly exposed Paleoproterozoic sandstones and siltstones of the Killi Killi Formation record developement of a large turbidite complex. Killi Killi Formation sediments were eroded from the uplifted ~1860 Ma Nimbuwah and Hooper Orogens as indicated by detrital zircons with sediment deposition at ~1840 Ma. Facies analysis, isopach maps and detrital zircon populations, combined with Sm-Nd data from the Tanami region and Halls Creek Orogen, confirm the previously suggested correlation of the Paleoproterozoic successions in the Eastern zone of the Halls Creek Orogen and the Tanami region. Detrital zircons from the Aileron Province suggest the turbidite complex extends into the Arunta region, however, high metamorphic grade precludes direct facies comparisons in the Arunta region. Portions of the turbidite complex in the Tanami region are dominated by mudstones, consisting of low-density turbidites and associated hemipelagites, that potentially acted as a redox boundary to gold-bearing fluid. Gold prospectivity in turbiditic systems is increased within these mudstone sequences with the potential for further gold discoveries.

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.

The following abstract was written in order to facilitate the compilation of the Queensland four-mile geological sheets and the explanatory notes accompanying them. The area described covers the Springsure, Emerald, Jericho and partly the Tambo and Baralaba four-mile sheets.

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.

Sequence biostratigraphic analyses from five industry wells in the Northern Carnarvon Basin (NCB) are tied to seismic stratigraphic interpretations from an exceptional set of 3D and 2D seismic data. We document distribution patterns of ~286 benthic and 73 planktonic foraminiferal taxa in sidewall cores and ditch cuttings from Eocene to Pliocene intervals and supplement this with observations of other fossil groups, e.g., ostracods, bryozoa, coral and mollusc fragments, and lithological components, such as, authigenic calcite and quartz sands. Preservation of foraminiferal assemblages is extremely variable in Oligocene to latest Miocene stratigraphy, depending upon location of wells and interval investigated. Nonetheless, consistent, detectable faunal signals correlate between wells, and with prominent seismic horizons and sequences. The late Oligocene to middle Miocene is characterized by deeper-water benthic assemblages dominated by infaunal taxa and higher planktonic to benthic ratios. A cluster of stratigraphic events in the middle Miocene, including turnover in benthic foraminifera, is interpreted to record a regional flooding event (equivalent to TB2.3) at the beginning of the mid Miocene climatic optimum (~16-14.5 Ma). Following this event, seismically-defined geomorphic features include intensive karstification and incision on the clinoform front. All wells show a major transition to shallow-water, warm conditions on the shelf in the middle and late Miocene, with benthic assemblages dominated by larger foraminifera. This transition occurs progressively later in more basinward wells and appears to be a result of progradation. Geomorphic features in the late middle Miocene (~12 Ma), identified from 3D seismic analyses, show an intensification of earlier gully formation, resulting in submarine canyons. Detailed analyses of faunal patterns also provide evidence of higher-frequency sea-level fluctuations (0.5-3 Ma), not detected in seismic stratigraphic patterns.