1 map showing the Acreage Release Title AC15-3 in the area of Overlapping Jurisdiction in the Perth Treaty. Requested by RET August 2014. LOSAMBA register 707

The Coompana Province is one of the most poorly understood pieces of crystalline basement geology in the Australian continent. It lies entirely concealed beneath a variable thickness of Neoproterozoic to Cenozoic sedimentary rocks, and is situated between the Gawler Craton to the east, the Musgrave Province to the north, and the Madura and Albany-Fraser Provinces to the west. A recently-acquired reflection seismic transect (13GA-EG1) provides an east-west cross-section through the southern part of the Coompana Province, and yields new insights into the thickness, seismic character and gross structural geometry within the Coompana Province. To assist geological interpretation of the 13GA-EG1 seismic line, new SHRIMP U-Pb zircon ages have been acquired from samples from the limited drill-holes that intersect the Coompana Province. New results from several granitic and gneissic rocks from the Coompana Province yield magmatic and/or high-grade metamorphic ages in the interval 1100 1200 Ma. Magmatic or high-grade metamorphic ages in this interval have not been identified in the Gawler Craton, in which the last major magmatic and metamorphic event took place at ~1590 1570 Ma. The Gawler Craton was largely unaffected by ~1100 1200 Ma events, as evidenced by the preservation of pre-1400 Ma 40Ar/39Ar cooling ages. In contrast, magmatic and metamorphic ages of 1100 1200 Ma are characteristic of the Musgrave Province (Pitjantjatjara Supersuite) and Madura Province (Moodini Supersuite). The new results from the Coompana Province have also yielded magmatic or inherited zircon ages at ~1500 Ma and ~1640 Ma. Once again, these ages are not characteristic of the Gawler Craton and no pre-1700 Ma inherited zircon has been identified in Coompana Province magmatic rocks, as might be expected if the province was underlain by older, Gawler Craton-like crust. The emerging picture from this study and recent work from the Madura Province and the Forrest Zone of the western Coompana Province is that the Coompana Province has a geological history that is quite distinct from, and generally younger than, the Gawler Craton to its east, but that is very similar to the Musgrave and Madura Provinces to the north and west. The contact between the Coompana Province and the Gawler Craton is interpreted in the 13GA-EG1 seismic line as a prominent west-dipping crustal-scale structure, termed the Jindarnga Shear Zone. The nature and timing of this boundary remain relatively poorly constrained, but the seismic and geochronological evidence suggests that it represents the western edge of the Gawler Craton, marking the western limit of an older, more isotopically evolved and multiply re-worked craton to the east, from a younger, more isotopically primitive crust that separates the South Australian Craton from the West Australian Craton.

1 map showing the Acreage Release Title W15-3 in the area of Overlapping Jurisdiction in the Perth Treaty. Requested by RET August 2014. LOSAMBA register 707

The Early Cretaceous Gage Sandstone and South Perth Shale are a prospective reservoir-seal pair in the Warnbro Group of offshore Vlaming Sub-basin, Western Australia. Gage Sandstone reservoir plays include post-breakup pinch-outs against the Valanginian Unconformity, and 4-way dip closures with the South Perth Shale forming the top seal. Deposited as a lowstand component of the deltaic South Perth Supersequence, the Gage Lowstand Fan (previously referred to as the Gage Sandstone) infilled palaeotopographic lows of the Valanginian breakup unconformity. Sequence stratigraphic analysis was used to characterise the reservoir-seal pair by integrating 2D seismic interpretation, well log analysis and new biostratigraphic data. Palaeogeographic mapping of the South Perth Supersequence reveal a series of regressions and transgressions that lead to the infilling of the central palaeodepression. The Gage reservoir is a sand-rich submarine fan system and ranges from canyon-confined inner fan deposits to middle fan deposits on a basin plain. Major sediment contributions were from north-south trending canyons adjacent to the Mandurah Terrace. More detailed seismic facies mapping and well log analysis of the Gage Lowstand Fan determined that the sand sheets in the distal middle fan and stacked channelized sands in the inner fan may provide an extensive reservoir of good to excellent quality. Seal quality varies greatly and may explain the lack of exploration success at some structural closures. A re-evaluation of the regional seal determined the extent of the pro-delta shale facies within the South Perth Supersequence that provides an effective seal for the underlying Gage reservoir. 3D geological modelling confirms that the Gage reservoir exhibits properties suitable for hydrocarbon entrapment and CO2 storage. Migration path analysis identified the presence of multiple structural and stratigraphic closures at the top of the Gage reservoir, with the most favourable located in the Rottnest Trough. Previous petroleum systems modelling concluded that the maturity of some source rocks in the sub-basin likely occurred after the deposition of the effective seal. Deep-seated faults, penetrating the syn-rift section, are in direct contact with the Gage reservoir and it could be actively receiving hydrocarbon charge.

Interpretative report from the GA0340/SOL5754 marine survey of the Leveque Shelf

This study demonstrates that seabed topography and geodiversity play key roles in controlling the spatial dynamics of large fish predators over macro-ecological scales. We compiled ten years of commercial fishing records from the Sea Around Us Project and developed continental-scale catch models for an assemblage of large open-water fish (e.g. tuna, marlins, mackerels) for Western Australia. We standardised catch rates to account for the confounding effects of year, gear type and species body mass using generalised linear models, from which relative indices of abundance were extracted. We combined these with an extensive array of geophysical, oceanographic, biological, and anthropogenic data to (1) map the location of pelagic hotspots and (2) determine their most likely mechanistic drivers. We tested whether submarine canyons promote the aggregation of pelagic fish, and whether geomorphometrics (measures of seafloor complexity) represent useful surrogate indicators of their numbers. We also compared predicted fish distributions with the Australian network of Commonwealth Marine Reserves to assess its potential to provide conservation benefits for highly mobile predators. Both static and dynamic habitat features explained the observed patterns in relative abundance of pelagic fish. Geomorphometrics alone captured more than 50% of the variance, and submarine canyon presence ranked as the most influential variable in the North bioregion. Seafloor rugosity and fractal dimension, salinity, ocean energy, current strength, and human use were also identified as important predictors. The spatial overlap between fish hotspots and marine reserves was very limited in most parts of the EEZ, with high-abundance areas being primarily found in multiple use zones where human activities are subject to few restrictions.

Large geochronological and geochemical data sets for the Paleo- to Mesoarchean Pilbara and Meso- to Neoarchean Yilgarn cratons, Western Australia, show that both cratons exhibit similar evolutionary trends in felsic magmatism, providing important constraints on Archean tectonics. The most obvious trend is a transition from sodic magmatismthe ubiquitous tonalite-trondhjemite-granodiorite (TTG) series with their high pressure (high-Al) signatureto potassic magmatism. In the Pilbara craton this transition is marked by two periods of potassic magmatism separated by 50 Myr. In the Yilgarn, the transition is mostly diachronous with potassic magmatism broadly younging to the west, except for one terrane where potassic magmatism begins ~40 Ma earlier. The change from sodic to potassic magmatism is, in part, a continuation of trends observable within the sodic granites themselves, which become more LILE-enriched with decreasing age. It is also evident in both cratons that magmatism derived from basaltic precursors is not confined to high-pressure formation of High-Al TTGs but includes lower pressure variants. The latter include low-Al TTGs (significant in the Pilbara Craton), and a group with high-HFSE and low- to moderate LILE-contents typical of A-type magmas. In the Yilgarn Craton such rocks form a locally common, often bimodal, association, representing formation at high-temperature and low-pressure. They are not often recognised as belonging to the sodic magmatic group but clearly reflect a magmatic pathway that starts with a largely mafic protolith, albeit at lower pressures and, unlike the low-Al TTGs, higher temperatures. Another shared trend is the appearance of a diverse group of rocks not unlike those seen in modern-day convergent tectonic settings. These comprise high-Mg diorites (or sanukitoids) (and related rocks), boninite-like rocks, `calc-alkaline basalts and andesites, calc-alkaline lamprophyres, but also syenites and monzonites. These rocks appear well after the first appearance of high- (and low-) Al TTGs and are most abundant just prior to major onset of potassic magmatism. In both cratons they are largely confined to younger linear geological terranes or marginal to/within the larger generally older terranes, and this, along with their enriched geochemistry permits the interpretation that they tap enriched mantle along crustal scale structures. Such rocks form a significant local component but overall are not abundant. The trends documented above are evident in many Archean terranes. The simplest way to explain the variation in the TTGs (high- and low-pressure variants) and the trends from sodic to potassic magmatism is via progressive reworking (maturation) of existing continental crust (for crustal-derived magmatism) and increasing involvement of felsic crust (for non-crustal magmatism). The chemical and isotopic evidence suggests a role for both mechanisms. It is, however, clear that crustal reworking played an early and persistent role in the compositional evolution of both the Pilbara and Yilgarn cratons (and probably Archean cratons in general), suggesting that models advocating a switch from slab-derived TTGs to crustal-derived potassic magmas are too simplistic. The appearance of magmas with an arc-like signature suggests that proto-subduction-like tectonic processes operated, at least intermittently, but not necessarily that they dominated Archean crustal evolution and crust formation.

Extended abstracts describing the preliminary interpretation of the Albany-Fraser orogen seismic and magnetotelluric datasets.

Miogypsina neodispansa (Jones and Chapman) is redescribed from oriented sections prepared from samples collected at the type locality on Christmas Island, Indian Ocean. and is referred to the subgenus Lepidosemicyc/ina. M.neodispansa is considered to be a senior synonym of M. droogeri Mohan and Tewari.

Detailed velocity/depth models of the crust of the Pilbara Craton have been produced from amplitude studies of refracted and reflected seismic waves and their travel-times. On three profiles, a near-surface high-velocity layer, in which the velocity sometimes reaches 6.65 km s-1, is interpreted as Hamersley Basin strata overlying the crystalline basement. The seismic velocity in the near-surface crystalline basement is about 6.0 km s-1, and increases with depth through the crust, reaching 6.1-6.2 km s-1 at 11-14 km depth. Below this , at about 15 km depth, a steeper gradient to 6.35-6.45 km s-1 defines an intracrustal seismic boundary. In the lower part of the crust, velocity gradients increase the velocity to 6.6-7.2 km s-1 . In some models, second-order velocity increases with depth are used to explain bright cusps in the data. although these could also be caused by topography on the crust/mantle boundary. The crust/mantle boundary is transitional over 4-5 km, and upper mantle (Pn) velocities range from 7.5 to 8.5 km s-1 . On one profile, a sub-Moho boundary at which the velocity increases from 8.2 to 8.35 km s-1 was recognised 14 km below the crust/mantle boundary. Previously published seismic models of the region show lateral inhomogeneity in the crust of the Capricorn Orogenic Belt, and this complicates a quantitative analysis of the amplitudes of seismic signals recorded in the orogen. However, a qualitative analysis based on the observed amplitudes, the positions of the ray-critical cusps of the previously published models , and the gravity field suggests that , while the intracrustal boundary at about 15 km depth may be sharp, the lower crust in the orogen must have high seismic velocities (and densities) and the crustal thickness in the previous models is probably not an overestimate. Increasing metamorphic grade with depth in the Yilgarn Craton probably ensures positive velocity gradients in the crust in the craton , so that the crustal thickness in the previously published models is considered reasonable. Thus, the interpreted large difference in crustal thickness between the Pilbara Craton (approximately 30 km) and the Yilgarn Craton ( 50 km) is substantiated.