Williams et al. (2009) report on new multibeam sonar bathymetry and underwater video data collected from submarine canyons and seamounts on Australia's southeast continental margin to 'investigate the degree to which geomorphic features act as surrogates for benthic megafaunal biodiversity' (p. 214). The authors describe what they view as deficiencies in the design of the Marine Protected Areas (MPAs) in the southeast region of Australia, in which geomorphology information was employed as a surrogate to infer regional-scale patterns of benthic biodiversity. This comment is designed to support and underscore the importance of evaluating MPA designs and the validity of using abiotic surrogates such as geomorphology to infer biodiversity patterns, and seeks to clarify some of the discrepancies in geomorphic terminologies and approaches used between the original study and the Williams et al. (2009) evaluation. It is our opinion that the MPA design criteria used by the Australian Government are incorrectly reported by Williams et al. (2009). In particular, we emphasise the necessity for consistent terminology and approaches when undertaking comparative analyses of geomorphic features. We show that the MPA selection criteria used by the Australian Government addressed the issues of false homogeneity described by Williams et al. (2009), but that final placement of MPAs was based on additional stakeholder considerations. Finally, we argue that although the Williams et al. (2009) study provides valuable information on biological distributions within seamounts and canyons, the hypothesis that geomorphic features (particularly seamounts and submarine canyons) are surrogates for benthic biodiversity is not tested explicitly by their study.

The Tonga subduction zone is among the most seismically active regions and has the highest plate convergence rate in the world. However, thrust events confidently located on the plate boundary have not exceeded Mw 8.0. The possibility of a low probability maximum magnitude event of Mw 8.6 to 9.1 has been raised, but a paucity of geodetic observations and their distance from the Tonga trench have precluded direct assessment of megathrust slip deficit accumulation. We analyze two major thrust fault earthquakes that occurred in central Tonga in 2006 and 2009. The 3 May 2006 Mw 8.0 event has a focal mechanism consistent with interplate thrusting, was located west of the trench, and caused a moderate regional tsunami. However, long-period seismic wave inversions and finite-fault modeling by joint inversion of teleseismic body waves and local GPS static offsets indicate a slip distribution centered ~65 km deep, about 30 km deeper than the plate boundary revealed by locations of aftershocks, demonstrating that this was an intraslab event. The aftershock locations were obtained using data from 7 temporary seismic stations deployed shortly after the mainshock, and most lie on the plate boundary, not on either nodal plane of the deeper mainshock. The fault plane is ambiguous and investigation of compound rupture involving co-seismic slip along the megathrust does not provide a better fit, although activation of megathrust faulting is responsible for the aftershocks. The 19 March 2009 Mw 7.6 compressional faulting event occurred below the trench; finite-fault and W-phase inversions indicate an intraslab, ~50-km deep centroid, with ambiguous fault plane. There continues to be a paucity of large megathrust earthquakes in Tonga.

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The microstructure of porous solid (sandstone reservoir rock) is described in terms of the continous pore size distribution, ranging from 10 Angstrom to hundreds of micrometres. The method combines statistical analysis of pore space images with small angle neutron scattering data and quantifies both fractal and euclidean features of the microstructure. A consistency of microstructural data with mercury porosimetry and NMR results obtained on the same rock sample is demonstrated.

Probabilistic seismic hazard analyses in Australia rely fundamentally on the assumption that earthquakes recorded in the past are indicative of where earthquakes will occur in the future. No attempt has yet been made to assess the potential contribution that data from active fault sources might make to the modelling process, despite successful incorporation of such data into United States and New Zealand hazard maps in recent years. In this paper we review the limited history of paleoseismological investigation in Australia and discuss the potential contribution of active fault source data towards improving our understanding of intraplate seismicity. The availability and suitability of Australian active fault source data for incorporation into future probabilistic hazard models is assessed, and appropriate methodologies for achieving this proposed.

A suite of 18 oils from the Barrow Island oilfield and a reference oil from Saladin-11 (Carnarvon Basin, Australia) have been analysed compositionally in order to determine the detailed effect of minor to moderate biodegradation on C5 to C9 hydrocarbons. Carbon isotopic data for individual low molecular weight hydrocarbons was also obtained for 6 of the oils. The Barrow Island oils came from different production wells, reservoir horizons, and compartments, but have a common source (the Upper Jurassic Dingo Claystone Formation). Ratios based on hopanes, steranes, alkylnaphthalenes and alkylphenanthrenes indicate thermal maturities of about 0.8% Rc for most of the oils. The co-occurrence in all the oils of relatively high amounts of 25-norhopanes with C5 to C9 hydrocarbons, aromatic hydrocarbons and cyclic alkanes implies that the oils are the result of multiple charging, with a heavily biodegraded charge being overprinted by fresher and more pristine oil. The later oil charge was itself variably biodegraded, leading to significant compositional variations across the oilfield which help delineate compartmentalisation. Biodegradation resulted in strong depletion of n-alkanes (>95%) from most of the oils. Benzene and toluene were partially or completely removed from the Barrow Island oils by water washing. However, hydrocarbons with lower water solubility were either not affected by water washing, or water washing had only a minor effect. etc etc (not enough space for all the Abstract)

Continental shelf margin habitats are increasingly being recognized worldwide for conservation and protection from human activities due to their biodiversity value. Yet, quantitative data on the biodiversity of the epibenthic taxa found on these continental shelf margins are scant. Consequently, this paper quantified the diversity of epibenthic taxa on an exposed- and sediment-inundated reef system located on the continental shelf margin off southeastern Australia as part of a program developing deep reef monitoring protocols. The reef system harbored a rich epibenthic taxa, with a total of 55 taxa identified from the images captured by an autonomous underwater vehicle. A Cnidaria/Bryzoa/Hydroid matix dominated the assemblages recorded. Taxa richness, diversity and evenness declined with distance from exposed reef ledge features, a characteristic geomorphic feature of this region. Patterns of the epibenthic assemblages were characterized by (1) taxonomic turnover at scales of 5 to 10's m from exposed reef ledges, (2) 30 % of epibenthic taxa were recorded only once (i.e. singletons), and (3) generally low levels of abundance of the component epibenthic taxa. This suggests that the assemblages in this region contain a considerable number of locally rare taxa, and potentially represent a high level of endemism. This study also highlights the importance of exposed reef ledge features in this region as they provide a refuge against sediment scouring and inundation in sediment-dominated ecosystems. Consequently, from a perspective of conservation planning for continental shelf habitats, protecting a single, or just a few, areas of reef are unlikely to accurately represent the geomorphic diversity of cross-shelf habitats and the epibenthic diversity that responds to this. Likewise, sampling needs to be adaptive, and stratified to incorporate known or suspected patterns relating to such variability. In this context, the data collected here provides a regional baseline dataset on the epibenthic taxa that shape the overall community structure for the Flinders Commonwealth Marine Reserve, and a guideline for sand-inundated cross-shelf reefs in general. Similar studies are now required for other known categories of cross-shelf reefs, including relict coastlines and complex block features more typical of igneous rock types.