In this review we aim to synthesise physical and biological information on the Lord Howe Rise (LHR) region to describe its biogeography at a regional scale (100s of kilometres) and assess this in a national and global context. The LHR region is large (1.95 million km2), spans tropical and cool temperate latitudes (18.4oS to 40.3oS), and is topographically complex being formed of large expanses of soft sediment basins and plateaus (i.e. subdued bathymetric features), with scattered seamounts, guyots, knolls, and pinnacles (i.e. raised bathymetric features). Physical factors can vary between these two broad feature types, particularly regarding depth and substrate, although no clear relationship was detected between sediment texture and geomorphic features across the survey area. Biological data from two recent surveys (TAN0713 and NORFANZ) show differences in assemblages and species distribution between raised and subdued bathymetric features and suggest that biological communities are indeed influenced by substrate as well as depth-related variables, with some taxa such as demersal fish showing latitudinal gradients. There are only limited spatially-replicated studies and no time-series data available for most of the LHR region, but paleo-environmental processes and examples from other regions provide some indication of migration, speciation, and endemism in the LHR region.

We provide here an updated geographic and stratigraphic framework of some of the Tertiary basins of central Australia. These have received little attention in the geological literature since the 1960s. This is due in part to the poorly outcropping nature of sequences within these basins, and to strong weathering overprints. As a consequence, this study depends heavily on analyses of drill hole cuttings, supplemented by a few cores. Drilling and reconnaissance geological mapping has shown that the basin sequences have been profoundly altered by weathering, with associated mineralogical and chemical changes. The sedimentary sequence also contains contemporaneous siliceous and calcareous beds, as well as redeposited or recycled sediments including former weathered and/orchemically precipitated rock types. This paper is, therefore, an attempt to unravel the complicated history of development of these basins. It provides a framework for reconstruction of the probable Cainozoic depositional, weathering, climatic and tectonic history of central Australia. Although there are large gaps in knowledge, the data presented has wide implications regionally for the palaeogeographic and tectonic evolution of the Australian Plate. Locally, it is valuable fo the assessment of mineral and groundwater resources.Many of the specific palaeo-environmental interpretations are tentative as, for example, details of the depositional, sedimentary, and stratigraphic details remain to be investigated.

Geodynamic modelling of selected aspects of the Bowen, Gunnedah, Surat and Eromanga basins constrains the mechanisms that were operating during their formation. For the Bowen and Gunnedah basins, a quantitative analysis of the early Late Permian to Middle Triassic foreland loading phase examined the relative roles of static loading versus dynamic loading associated with the convergent plate margin. Subsidence in the initial foreland phase in the early Late Permian is consistent with platform tilting due to corner flow in the mantle associated with west-directed subduction. Later in the Late Permian, platform tilting probably continued to be the dominant cause of subsidence, but increasing amounts of subsidence due to foreland loading occurred as the thrust front in the New England Orogen migrated westward. In the latest Permian and Early Triassic, static flexural loading due to foreland loads is dominant and may be the sole cause for basin subsidence. For the Surat and Eromanga basins, the tectonic subsidence across an east-west transect is modelled to assess the contribution of dynamically-induced platform tilting, due to viscous mantle corner flow, in basin subsidence. The modelling suggests that subsidence was again controlled by dynamic platform tilting, which provides a mechanism for both the nearfield and farfield effects. Uplift of the Eastern Highlands in the mid-Cretaceous may also be related to viscous corner flow driven by west-directed subduction beneath eastern Australia, with the uplift being due to rebound of the lithosphere after the cessation of subduction.

Legacy product - no abstract available

Abstract for initial submission; see Geocat 71429 for conference paper version

This report is a description of velocity data acquired during the summer of 2006/07 on Geoscience Australia's seismic marine reflection, refraction and potential field survey GA302 over the Capel and Faust Basins, Lord Howe Rise. The survey was the final phase of the Australian Government's Big New Oil initiative commenced in 2003 to support acreage release in frontier basins. Previous data over the region are sparsely located, and the present survey will provide explorers with high quality data acquired and processed to modern standards. The Lord Howe Rise is thought to be a continental fragment detached from Australia during the formation of the Tasman Sea. The Capel and Faust Basins are of interest as possible frontier petroleum provinces, and the present work is aimed at improving the confidence of sediment thickness estimation, a critical parameter in evaluating of prospectivity. The study reviews the seismic reflection data from survey GA302, the sonobuoy refraction data acquired, and the stacking velocities from the seismic reflection processing.

This presentation summarises results of 3d petroleum systems modelling of the northwestern Ceduna Sub-basin, Bight Basin, offshore southern Australia, using Schlumberger Petromod software. The model builds on two 2D models for the northern and central Ceduna Sub-basin published in Totterdell et al. (2008).

The seismic stacking velocity data in the Great Australian Bight are a useful dataset for calculating depths and sediment thicknesses. This work presents time-depth relationships computed from an unfiltered stacking velocity database and compares these with depths from sonobuoy P-wave velocities and exploration well sonic logs. The comparison suggests that a total sediment thickness over-estimate for the Ceduna Sub-basin of about 15% can be expected from the depths derived from stacking velocities. On the other hand, for sediment thickness calculations down to ~4 s two-way travel time below sea floor, stacking velocity data give comparable depths to those obtained from the wells' sonic logs. A piece-wise formula is offered which scales the time-depth function for the Ceduna Sub-basin in order to compensate for the depth overestimate inherent in using stacking velocities to calculate total sediment thickness. Megasequence boundary depths are calculated for the Ceduna Terrace to further illustrate data quality.

This record contains the results of a geological framework study of the southern half of the Lord Howe Rise and adjacent areas, including the Tasman Basin and the New Caledonia Basin. The report particularly focuses on the geological evolution and the resource potential.

The seismic stacking velocity data in the Otway Basin are a useful dataset for calculating depths and sediment thicknesses. This work presents time-depth relationships computed from unsmoothed stacking velocities and compares these with functions obtained from sonobuoy refraction data and exploration well sonic logs. The comparison suggests that a total sediment thickness over-estimate for the Otway Basin of about 15% can be expected from the depths derived from stacking velocities alone. On the other hand, for sediment thickness calculations down to ~3 s two-way travel time below sea floor, stacking velocity data give comparable depths to those obtained from the sonic logs. A piece-wise formula is offered which scales the time-depth function for the Otway Basin in order to compensate for the depth overestimate inherent in using stacking velocities to calculate total sediment thickness.