Potential Field Datasets Research Articles

Potential fields as a tool to characterize the inaccessible areas of the earth: The case of Pine Island–Ellsworth Mountains area, West Antarctica

We seek to characterize the geophysical properties of the West Antarctic Rift System. While it is recognized as one of the largest rift systems on the earth, the West Antarctic Rift System is poorly understood as it is covered by the thick West Antarctic Ice Sheet, making any geologic evaluation difficult. We used the potential-field data sets acquired by the British Antarctic Survey, which included aeromagnetic surveys, to conduct a multiscale analysis to identify the main structural lineaments, i.e., contacts, dikes, sills, volcanic necks and conduits, and spherical source distributions. Several interesting areas were defined in which contact-type sources were associated with faults bordering major rift systems (Pine Island, Byrd Subglacial Basin, and Bentley Subglacial Trench) or related to the tributaries in the Pine Island Rift. Moreover, we detected magmatic sources close to rifting zones based on their shape and orientation (Bentley Subglacial Basin edges), helping to define the depth of the sub-ice topography. Our results helped improve our knowledge of the structural regional geology of the West Antarctic Rift System. This work opens interesting scenarios about the extent and position of magmatic sources and how they contribute to the topography of this sector of the West Antarctic Rift System.

Structural analysis and measured extension in fault complexes along the Lofoten‐Vesterålen margin, offshore Norway, in the context of crustal‐scale rifting towards breakup in NE Atlantic

AbstractLate Cretaceous–Palaeocene continental extension within the Lofoten‐Vesterålen margin is investigated by integrating 2D‐3D seismic and potential field datasets, together with updated crustal transects. Most of that deformation is recorded by two low‐angle detachment structures named West Røst High Fault Complex (WRHFC) and North Utrøst Ridge Fault Complex (NURFC) located at the southern and central‐northern portions of the studied area, respectively. Multiple extensional episodes of various intensities were mapped as different fault stages, including one Albian‐Cenomanian phase, four early Late Cretaceous phases, three Late Cretaceous to latest Cretaceous–Palaeocene phases, and one Palaeocene phase. The WRHFC is narrower in extent and has accommodated a relatively greater amount of localized extension (ca. 18–19 km), whereas the NURFC occupies a wider area with widespread extension intensity (ca. 6–8 km). In comparison, the total across‐margin average extension within the southern, central, and northern portions of the Lofoten‐Vesterålen and NE Greenland conjugate margins are ca. 192, 221, and 266 km, respectively. Such results indicate an apparent extension discrepancy between derived extension from measured fault‐block geometries within the fault complexes and the whole conjugate margin system, with only ca. 11% and 13% of the extension seen on the studied seismic profiles on the WRHFC and NURFC, respectively. The corrected maximum extension for purely sub‐seismic resolution faulting on both the WRHFC and NURFC fault complexes is ca. 164 and 46 km, respectively. Finally, both WRHFC and NURFC structures provide key evidence for a ductile mode of deformation towards breakup that is expressed through shear zones‐rift topography interactions with overlaying listric/detachment faults. These features reflect the resulting multiphase tectonic evolution across the asymmetric Lofoten‐Vesterålen and NE Greenland conjugate margins, and the obliquity in the breakup axis location along them. The study outcomes are pertinent and applicable to understand the breakup evolution of the northern NE Atlantic and its vicinity.

Towards a better understanding of the recoverability of physical property relationships from geophysical inversions of multiple potential-field data sets

SUMMRY Collecting multiple potential-field data sets to image the subsurface has been popular in resource explorations. How to effectively integrate multiphysics data and extract useful information about the subsurface geology is an active area of research. Among existing approaches, geophysical inversions followed by geological classification has shown promising results. This procedure contains two steps. First, multiple geophysical data sets are inverted, either separately or jointly, to obtain their corresponding physical property models. Secondly, the inverted values are visualized in a scatterplot and classified into different groups, a process known as geology differentiation. The implicit assumption for geology differentiation is that the recovered physical property relationships are reliable. However, whether this assumption is generally valid or not remains unknown. Moreover, it is well known that the standard smooth inversion would underestimate the physical property values. On the other hand, the sparse inversion is able to recover compact anomalies with elevated magnitudes. However, it remains unclear as to how smooth and sparse inversions affect the recoverability. To understand the recoverability of physical property relationships, we have designed six geological scenarios with three geological anomalies located at different depths and assigned with different physical property values. For each scenario, we performed four inversions: both separate and joint inversions using smooth L2-norm and sparse mixed L12-norm regularizations. Each inversion is followed by geology differentiation. We have found (1) that the recovered physical property relationships from geophysical inversions are not always reliable, (2) the depths of the source bodies and inversion strategies significantly affect the recoverability, and (3) joint sparsity inversion consistently gives rise to the best recoverability.

Insights and Lessons from 3D Geological and Geophysical Modeling of Mineralized Terranes in Tasmania

Over the last two decades, Mineral Resources Tasmania has been developing regional 3D geological and geophysical models for prospective terranes at a range of scales and extents as part of its suite of precompetitive geoscience products. These have evolved in conjunction with developments in 3D modeling technology over that time. Commencing with a jurisdiction-wide 3D model in 2002, subsequent modeling projects have explored a range of approaches to the development of 3D models as a vehicle for the better synthesis and understanding of controls on ore-forming processes and prospectivity. These models are built on high-quality potential field data sets. Assignment of bulk properties derived from previous well-constrained geophysical modeling and an extensive rock property database has enabled the identification of anomalous features that have been targeted for follow-up mineral exploration. An aspect of this effort has been the generation of uncertainty estimates for model features. Our experience is that this process can be hindered by models that are too large or too detailed to be interrogated easily, especially when modeling techniques do not readily permit significant geometric changes. The most effective 3D modeling workflow for insights into mineral exploration is that which facilitates the rapid hypothesis testing of a wide range of scenarios whilst satisfying the constraints of observed data.

Margin-to-Margin Seafloor Spreading in the Eastern Gulf of Aden: A 16 Ma-Long History of Deformation and Magmatism from Seismic Reflection, Gravity and Magnetic Data

In this paper we present and analyze spreading-parallel seismic transects that image the oceanic crust in the eastern Gulf of Aden, from the Oman to the Socotra margins, across the active Sheba mid-oceanic ridge and between the Socotra-Hadbeen and Eastern Gulf of Aden Fracture Zones. The correlation of potential field data sets and gravity modelling allow us to document the spreading history of this oceanic basin from the onset of seafloor spreading ∼16 Ma-ago to the present. Two main oceanic sub-domains display distinct structural characteristics associated with different magmatic budgets at this mid-ocean ridge. In addition, we document the occurrence of a magmatic pulse at the Sheba Ridge around 11 Ma leading to the construction of a magmatic plateau in the western part of the studied area. This event led to substantial deformation and additional magmatism in previously formed oceanic crust. It could be related to an off-axis magmatic event previously identified in the adjacent Sheba segment, itself possibly related to the Afar plume.

Processing and interpretation of full tensor gravity anomalies of Southern Main Ethiopian Rift

The study area is situated in the Southern Main Ethiopian Rift being bounded within the limit of 37o00″0′-38o50′00″E and 5o50′00″-7o00′00″N. It is well known that the complex geological structure of the Main Ethiopian Rift has attracted intense attention so far and numerous geophysical investigations have been performed using potential field data-sets in Central and Northern Main Ethiopian Rift with the exception of the Southern Main Ethiopian Rift which is poorly constrained. Analysis of Full Tensor Gravity anomalies helps in understanding of the nature of shallow subsurface structural features and has a paramount importance in building general understanding of subtle details about subsurface geology of the area.Separation of regional and residual gravity field is performed using upward continuation filtering technique. The residual gravity anomaly caused by local structures and anomalous body delineated four sub-basins with low amplitude response which is in agreement with the vertical gravity gradient anomaly (Gzz) and tilt derivative horizontal (TDX) that clearly outlined and characterize edges of the sub-basins. The sub-basins delineated are the northern and southern Abaya, Chamo and Gelana basins. The tilt angle method which is used to delineate major subsurface structures and determine the source depth results showed that the area was affected by different lineament trending NE-SW, N–S, NNE-SSW, NW-SE and E-W, directional analysis performed indicates that the dominant trend is in agreement with the regional fault orientations. The estimated depth to the top of the lineaments on average varies from 0.9 km to 3.1 km and it is relatively deeper in the basins compared to the surrounding areas giving clues to the amount of sediment infill.

A comparative study of THG, AS, TA, Theta, TDX and LTHG techniques for improving source boundaries detection of magnetic data using synthetic models: A case study from G. Um Monqul, North Eastern Desert, Egypt

The boundaries detection techniques have a great role in enhancing and interpreting the geologic features of magnetic data. In the literature, several filters (THG, AS, TA, NTilt, Theta, TDX, TAHG, LTHG) for identifying the boundaries of the magnetic sources have been suggested. These methods are generally performed based on gradients (vertical and horizontal) of the potential field. This paper presents a comparative investigation of different boundary detection filters including THG (total horizontal gradient), AS (analytical signal), TA (tilt angle), Theta (Cos θ), TDX (horizontal tilt angle), and LTHG (Logistic function of the THG). The effect of each filter was examined on two synthetic magnetic data sets. Moreover, the filters are also applied to a real magnetic data set from the Gabal (G) Um Monqul, North Eastern Desert (NED) of Egypt. The obtained results were correlated with known geologic structures of the study area. From the comparison between several applied methods, the horizontal boundaries of geologic sources obtained by the LTHG were found to be sharper and clearer than other ones. The results confirm that the LTHG method is an effective filter for interpreting aeromagnetic data qualitatively and can be applied for enhancing the source edges of different potential field datasets.

Interpretation of buried basement in the southwestern Athabasca Basin, Canada, from integrated geophysical and geological datasets

Recent discoveries of basement-hosted uranium deposits in the Patterson Lake corridor in the southwestern Athabasca Basin of Canada have brought vigorous exploration interest to the region. New lithostratigraphic constraints, geochronology and airborne geophysical surveys have dramatically improved the understanding of the host basement geology, warranting a re-examination of the remote predictive mapping and geophysical responses of the buried basement rocks. This study took a two-step approach to examine the regional basement geology and architecture. First, a mosaic of the long-wavelength response of potential field (gravity and magnetic) datasets was examined to divide the basement into regional domains based on bulk physical property variations. The interpretive geological model was then refined using textural and lineament analysis of new airborne gravity and magnetic datasets, geological drill hole logs and magnetic susceptibility measurements. The new basement map identifies and updates major features including a crustal-scale structure that separates the southern Tantato Domain from the newly defined eastern Taltson Domain. This structure may have played a role in localizing fluid flow in the Patterson Lake corridor, defining the spatial extents of structurally controlled buried felsic intrusions, and redefines the boundaries of the Taltson, Clearwater and Tantato Domains. In addition, the potential field enhancements delineated significant regional faults that controlled the geometry of Paleoproterozoic cover sequences and have implications for understanding the crustal architecture of the southern Rae Province. These new interpretations shed light on the tectonic history of the region to support on-going exploration activities and delineate regionally prospective areas in this understudied area of the Canadian Shield. Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways

Strategic electromagnetic geophysical prospecting across a belt - an example over the Albany Fraser Orogen

SummaryNickel exploration routinely utilises electromagnetic (EM) techniques as a direct detection tool. Independence Group is currently exploring a large tenement holding in the Albany Fraser Orogen in Western Australia that contains its flagship Nova magmatic nickel-copper-cobalt deposit. As a first-pass exploration stage, large-scale high-resolution airborne EM is being flown over the project using the Spectrem system. Interpreted discrete basement conductors are then followed up with ground EM surveys. In areas of conductive regolith cover identified from the airborne EM surveys, other datasets are used to determine if subsequent EM is warranted. Such methods include regional aircore geochemistry and/or through favourable lithostructural settings interpreted from high resolution potential field datasets. This program of regional data collection is nearly complete, and a follow-up drilling program is starting in earnest this year. This paper includes a couple of examples of the geophysical targets drill tested to date.

Parameter Estimations from Gravity and Magnetic Anomalies Due to Deep-Seated Faults: Differential Evolution versus Particle Swarm Optimization

Estimation of causative source parameters is an essential tool in exploration geophysics and is frequently applied using potential field datasets. Naturally inspired metaheuristic optimization algorithms based on some stochastic procedures have attracted more attention during the last decade due to their capability in finding the optimal solution of the model parameters from the parameter space via direct search routines. In this study, the solutions obtained through differential evolution algorithm, a rarely used metaheuristic algorithm in geophysics, and particle swarm optimization, which is one of the most used global optimization algorithms in geophysics, have been compared in terms of robustness, consistency, computational cost, and convergence rate for the first time. Applications have been performed using both synthetic and real gravity and magnetic anomalies due to deep-seated fault structures. Before the parameter estimation studies, resolvability of the fault parameters have been examined by producing cost function/error energy topography maps to understand the suitability of the problem and also the mathematical nature of the inversion procedure. Optimum control parameters of both algorithms have also been determined via some parameter tuning studies performed on synthetic anomalies. Consequently, the tuned parameters clearly improved the effectiveness of both metaheuristics on the solution of the optimization problems under consideration. Moreover, reliabilities of the obtained solutions and also the possible uncertainties have been investigated using probability density function analyses. Real data applications have been performed using a residual gravity anomaly observed over the Graber oil field (Oklahoma, USA) and an airborne total field magnetic anomaly observed over the Perth Basin (Australia). Applications have shown that although both algorithms provided close results in both synthetic and real data experiments, the differential evolution algorithm yielded slightly better solutions in terms of robustness, consistency, computational cost, and convergence rate. Thus, the differential evolution algorithm is worth paying more attention to and is suggested as a powerful alternative to particle swarm optimization for the inversion of potential field anomalies.

Interpretation of gravity anomalies to delineate some structural features of Biga and Gelibolu peninsulas, and their surroundings (north-west Turkey)

On the basis of gravity data, derived anomaly traces were presented for the interpretation of some shallow structural features of Biga and Gelibolu peninsulas. Since building general understanding of subtle details about subsurface geology is of great importance considering that the study area is tectonically important, some advanced data processing techniques were implemented to gravity anomalies in a detailed manner. The procedures were performed using a MATLAB-based software package (Gravity and Magnetic Interpretation – GMINTERP). First, a finite element method was utilised to produce the residual data-set which is expected to reflect short wavelength anomalies arising from shallower geological structures, and thereafter some derivative-based algorithms were executed to analyse the residual data. The general anomaly patterns obtained from the applications clearly corresponded to the well-known surface geology map of the study area. Derivative-based anomaly maps put forward some findings about the existence of an old caldera structure in the western part of the Biga Peninsula. Additionally, abrupt lateral changes in anomaly amplitudes indicated the presence of some major structural discontinuities. Thus, findings yielded to make significant geological interpretations that might be important for further investigations. This study also showed that GMINTERP software package proved useful in assisting geological interpretation using geophysical potential field data-sets.

Denoising magnetic data using steering kernel regression

ABSTRACTGround‐based magnetic surveying is a common geophysical method to explore near‐surface environments in a non‐destructive manner. In many typical applications (such as archaeological prospection), the resulting anomaly maps are often characterized by low signal‐to‐noise ratios and, thus, the suppression of noise is a key step in data processing. Here, we propose the steering kernel regression (SKR) method to denoise magnetic data sets. SKR has been recently developed to suppress random noise in images and video sequences. The core of the method is the steering kernel function which represents a robust estimate of local image structure. Using such a kernel within an iterative regression based denoising framework, helps to minimize image blurring and to preserve the underlying structures such as edges and corners. Because such filter characteristics are desirable for random noise attenuation in potential field data sets, we apply the SKR method for processing high‐resolution ground‐based magnetic data as they are typically collected in archaeological applications. We test and evaluate the SKR method using synthetic and field data examples and also compare it to more commonly employed denoising strategies relying, for example, on fixed filter masks (e.g., Gaussian filters). Our results show that the SKR method is successful in removing random and acquisition related noise present in our data. Concurrently, it preserves the local image structure including the amplitudes of anomalies. As demonstrated by derivative based transformations, the mentioned filter characteristics significantly impact subsequent processing steps and, therefore, result in an improved analysis and interpretation of magnetic data. Thus, the method can be considered as a promising and novel approach for denoising ground‐based magnetic data.

Geomagnetic and geoelectrical prospection for buried archaeological remains on the Upper City of Amorium, a Byzantine city in midwestern Turkey

On the basis of geophysical imaging surveys, including geomagnetic and geoelectrical resistivity, possible archaeological remains and their spatial parameters (i.e., location, extension, depth and thickness) were explored to provide useful data for future excavations on the Upper City of the ancient Amorium site, which comprises a large prehistoric man-made mound. The surveys were performed very close to the main axis of the Basilica, and the derived geophysical traces indicated some subsurface structures that appear to confirm that more-substantial brick and masonry buildings lie near the present-day surface of the mound. Analyzing the local gradients by total horizontal derivatives of pseudogravity data enhanced the edges of the magnetic sources. Additionally, a profile curvature technique, which has rarely been applied to potential field data sets, dramatically improved the magnetic-source body edges and the lineaments that may be associated with buried archaeological remains. The depths of these possible anthropogenic remains were estimated by applying the Euler deconvolution technique to the geomagnetic data set. The Euler solutions on tentative indices indicated that the depths of the source bodies are not more than about 3 m. Moreover, geoelectrical resistivity depth slices produced from the results of two- and three-dimensional linearized least-squares inversion techniques revealed high-resistivity anomalies within a depth of about 3 m from the ground surface, which is in close agreement with those obtained by applying the Euler deconvolution technique to the magnetic data. Based on the existence of some archaeological remains in the vicinity of the surveyed area, these geophysical anomalies were thought to be the possible traces of the buried remains and were suggested as targets for excavations. This study also emphasized that the data-processing techniques applied in this investigation should be suitable for providing an insight into the layout of the unexcavated parts of the Amorium site.

Joint inversion of gravity, magnetic, and petrophysical data — A case study from a gabbro intrusion in Boden, Sweden

We have studied a gabbro intrusion in northern Sweden, using 3D inversion of airborne magnetic data, ground-based gravity data, and petrophysical measurements on outcrop samples. Gabbro intrusions are of interest because they are potential hosts of Cu-Ni and platinum group element mineralization. We developed a joint inversion algorithm and applied it to both potential-field data sets to obtain spatial distributions of density and magnetic susceptibility. The distributions were coupled through a nonrigidly enforced parameter relationship determined from the petrophysical samples. We managed the problem of balancing the influence of the two data sets by a novel adaptive reweighting scheme that enforced the discrepancy principle for each data set independently. We demonstrated in tests with synthetic data that neither individual nor joint inversions gave reliable estimates for the depth extension of the intrusive body, the near-surface details, or any complex geometrical features. However, the joint inversion improved the image of the interface between the intrusion and the surrounding rocks and revealed that the density and susceptibility models satisfied the observed petrophysical relationship, which, in turn, caused the structures in the models to align. The geometry of the intrusion was an intrinsic result of the inversion, based on the two distinct petrophysical trends for the gabbro and the surrounding rocks. The inferred shape was simple and concise, and was therefore a useful and testable hypothesis about the subsurface geology that was in agreement with both potential-field data sets and the petrophysical information.

An assessment of the Performance of Derivative Based Data Enhancement Techniques in the Presence of Coherent Noise

SUMMARY Enhancement of potential field datasets using operators based on one or more of the spatial derivatives is common practice. The performance of these methods in the presence of noise is poorly understood; other than a general acceptance that they can be significantly affected, especially when higher order derivatives are used. Most published descriptions which involve noise tests use random noise and a dense and uniform sampling of the test region. More realistic tests of the effects of noise should account for the incomplete and anisotropic sampling within most datasets and also correlated noise such as due to incorrect levelling. An understanding of the effects of noise on the different methods of enhancement is particularly important when working with lower quality (older) and lower resolution datasets. Interpretation of geophysical data from West Africa, as part of a major project on the prospectivity of the region, is being undertaken. Much of the data available is of relatively low quality and resolution. An important component of the work will involve determining how best to enhance the gravity and magnetic datasets. Initial results working on gridded data show that the generalized derivative operator is the most robust derivative based enhanced product for low resolution data.

The application of spatial derivatives to non‐potential field data interpretation

ABSTRACTSource/body edge detection is a common feature in the processing and interpretation of potential field data sets. A wide range of spatial derivatives is available to enhance the information contained in the basic data. Here the ability of these procedures to assist with the mapping interpretation of non‐potential field data is considered. The study uses airborne electromagnetic (conductivity) data but also provides a general context for other conductivity/resistivity data, provided the non‐potential field nature of active and thus spatially‐focused, measurements is acknowledged. The study discusses and demonstrates the application of a range of common spatial derivative procedures, including the analytic signal and upward continuation, to both magnetic and conductivity data. The ability of the tilt derivative to provide enhanced mapping of conductivity data is considered in detail. Tilt and its associated functions are formed by taking combinations of vertical and horizontal derivatives of the data set. Theoretical forward modelling studies are first carried out to assess the performance of the tilt derivative in relation to the detection and definition of concealed conductivity structure. The tilt derivative embodies automatic gain control that normalizes the detection and definition of both weak and strong conductivity gradients across an appropriate subsurface depth range. The use of high‐order spatial derivatives inevitably results in a degree of noise (cultural perturbation) amplification that is survey and technique specific. Both of these aspects are considered using practical case studies of jointly obtained magnetic and conductivity data at a variety of spatial scales.

Airborne Gravity & Magnetics – A fast track multi-system approach for petroleum exploration

Recent advances in mapping technologies coupled with the emerging needs of the exploration industry to precisely characterize the sub-surface systems, have led to the resurgence in interest for gravity and magnetic (so called potential field) methods in oil and natural gas exploration. The need for acquiring large potential field data sets at greater speed over highly prospective and frontier areas is increasing the demand for airborne measurement systems. In response to this need, UTSAeroquest offers the latest version of airborne gravity systems called TAGS (Turnkey Airborne Gravity System) on a fixed wing geophysical survey aircraft, which is already equipped with a magnetic acquisition system as well as radar and laser altimeters. Prior to offering the services of this new system, a pre-purchase test of the gravity meter was undertaken. The results provided a high level of confidence in offering this multisystem airborne geophysical approach to the petroleum industry.

Basin geometry and salt diapirs in the Flinders Ranges, South Australia: Insights gained from geologically-constrained modelling of potential field data

The Adelaide Basin in Australia is a complex of late Neoproterozoic to Early Cambrian rift and sag basins which was inverted during the Cambro–Ordovician Delamerian Orogeny. The deposition of evaporitic sediments during the earliest stage of basin development in the late Neoproterozoic (Willouran age) played a major role in the subsequent tectonic evolution of the basin. Previous studies have shown that early mobilization, vertical transport and withdrawal of the evaporites influenced the sedimentation during the late Neoproterozoic and Early Cambrian. The evaporites also influenced deformation during the inversion of the basin and the development of the Delamerian fold and thrust belt. However, the control exerted by basement structures in the deposition of the evaporitic beds and the role of these tectonic structures in the later inversion of the basin have been poorly constrained. In this work, we use a combination of published and original geological observations along with the interpretation of potential field datasets (total magnetic intensity and Bouguer anomaly data) to better constrain the geology of the basin at depth. We construct two and a half dimensional forward models of the potential field data along selected profiles across the Adelaide Basin. These models are constrained by the geology at the surface, drill hole data and measured petrophysical properties (specific gravity and magnetic susceptibility). We achieved the best fit between observed and modelled potential fields with a model favouring thick-skinned deformation, where the diapirs are not randomly distributed, but located directly above basement-penetrating normal faults. Furthermore, these normal faults were probably active during the sedimentation of the late Neoproterozoic and Early Cambrian sediments, and underwent partial or total inversion during the Cambro–Ordovician Delamerian Orogeny. Mobilisation and withdrawal of the evaporites was therefore initiated and facilitated by the extension coeval with the opening of the basin, and continued during the subsequent Delamerian Orogeny.

Capel and Faust basins—integrated geoscientific assessment of Australia's remote offshore eastern frontier

The paper discusses the results from the GA–302 2D seismic survey and GA–2436 (RV Tangaroa) marine reconnaissance survey over the Capel and Faust basins in the northern Tasman Sea. The integration of seismic, potential field and bathymetric data sets in 3D space at an early stage in the project workflow has assisted in the visualisation of the basin architecture, the interpolation of data between the seismic lines and the iterative refinement of interpretations. The data sets confirm the presence of multiple depocentres previously interpreted from satellite gravity data with a maximum sediment thickness of 5–7 km. Preliminary interpretation of the seismic data has identified two predominantly Cretaceous syn-rift and two Upper Cretaceous to Neogene sag megasequences overlying a heterogeneous pre-rift basement. The comparison of seismic facies and tectonostratigraphic history with offshore New Zealand and eastern Australian basins suggests the presence of possible Jurassic to Upper Cretaceous coaly and lacustrine source rocks in the pre-rift and syn-rift, and fluvio-deltaic to shallow marine reservoir rocks in the syn-rift to early post-rift successions. Preliminary 1D basin modelling suggests that the deeper depocentres of the Capel and Faust basins are within the oil and gas windows. Large potential stratigraphic and structural traps are also present.

Structural transect and forward modelling of geophysical data across the St Arnaud Group, Victoria

The integration of detailed field mapping with 2.75D forward modelling and worming of potential-field datasets has constrained the 3D geometry of regionally significant faults and allowed a detailed understanding of the crustal-scale architecture of the St Arnaud Group in the Stawell Zone to be developed. The forward modelling has also highlighted the existence of a major west-dipping, non-outcropping fault, the Burrom Fault, between the Concongella and Landsborough Faults. The structure of the upper crust is characterised by major reverse faults. These faults originate from a basal décollement that is located within mafic volcanics underlying the St Arnaud Group. Deformation has resulted in slices of these mafic volcanics being ramped up along the traces of the major faults.