Fluvial sediments, here assigned to the Bergalia Formation, adjacent to the middle reaches of the Clyde River near Batemans Bay on the New South Wales south coast were deposited prior to a basalt valley flow with K–Ar ages averaging 27.7 ± 0.3 Ma. Similar Bergalia Formation sediments are preserved near Mogo, south of Batemans Bay, and suggest that the Clyde River flowed south through the Mogo area prior to diversion to the east. The diversion resulted from local‐scale neotectonic movements or sea‐level changes after the mid‐Oligocene. The previously undescribed deposits at these two locations provide evidence that relief comparable to or greater than the present existed in the Clyde River valley by this time. The basalt and sediments in the Clyde River valley indicate that the coastal lowlands in southeast New South Wales were developed prior to the mid‐Tertiary period.
Since 1958 the Ground-Water Surveillance Program for the Hanford Site has made geophysical logging measurements in most of the 800 wells and deep boreholes that have been drilled on the Hanford Site. In 1980 the Pacific Northwest Laboratory (PNL), which conducts the Ground-Water Surveillance Program, began forming a computerized data base for storing and retrieving geophysical well log data and developing software for quantitative analysis of the well log data. This report, designed to serve as a user's guide, documents the data base system that handles the well log data. Two programs, DIGLOG1 and LOGIT, are used to manipulate the data. The program DIGLOG1 translates analog paper strip charts into digital format; the program LOGIT is a general utility program that edits, displays, checks, stores, writes, and deletes sets of well log data. These two programs do not provide sophisticated display and analytical capabilities; rather, they provide programs that give the user easy access to powerful standard analytical software.
Apatite fission track thermochronology (AFTT) and paleomagnetic (PM) results have been used to constrain the Late Paleozoic to Cenozoic landscape evolution of the Lachlan Fold Belt (LFB) around the Northparkes copper-gold deposit in east-central New South Wales. The present-day landscape of this region of the LFB is relatively flat with little expression of the underlying rock and has previously been interpreted to indicate long-term stability of the region since the end of LFB orogenesis in the Early Carboniferous. This was presumably borne out by PM analyses from thick weathered horizons within open pits at the mine, which suggested that significant periods of weathering, and hence relative landscape stability, prevailed during the Early to middle Carboniferous and at some time during the Cenozoic. Results from AFTT analyses, however, indicate that the region must have experienced significant episodes of cooling/denudation during the mid-Permian to mid-Triassic and during the early Cenozoic, as well as episodes of heating/burial during the Late Carboniferous to mid-Permian and during the late Mesozoic. When combined, the AFTT and PM results are in fact consistent and indicate that since the late Paleozoic the landscape of the LFB around the Northparkes deposit has evolved through multiple episodes of denudation and deposition as well as periods of relative stability during which the thick weathering horizons formed. Together these results establish a complementary chronological framework that constrains the Late Palaeozoic to Cenozoic landscape evolution of the Northparkes region and highlights the importance of using dual data sets in elucidating the long-term landscape evolution of similar "stable" terranes.
A recent paradigm shift has occurred in our understanding of the importance of Neogene intra-plate tectonics for surface hydrology and groundwater systems in Australia. While active deformation zones are readily identified by seismicity monitoring and high-resolution satellite and airborne terrain mapping, advances in airborne electromagnetic (AEM) technology and data optimization have enabled rapid mapping of more extensive 'blind' Neogene intra-plate fault systems in the near-surface within seismically quiescent depositional landscapes. However, to date, the geometries, displacements, and properties of these Neogene faults have remained ambiguous due to a paucity of outcrop, AEM footprint resolution, and the non-uniqueness of the conductivity models and derived hydrostratigraphy and fault geometry solutions produced by AEM equivalent inversion models. In this study, a novel, inter-disciplinary approach has been developed to characterise the hydrogeology of intra-plate fault systems within unconsolidated, near-surface depositional landscapes and underlying sedimentary basins. The approach integrates morphotectonic analysis with sub-surface mapping of hydrostratigraphy and 'blind' intra-plate fault systems using airborne geophysics (AEM, airborne magnetics) and satellite remote sensing (e.g. Landsat). Fault zone geometry and displacement is examined using both 1D and 2.5D inversions of AEM data, validated at local scales by ground geophysics (e.g. seismic reflection, resistivity and ground nuclear magnetic resonance (GMR)) and drilling. Fault zone hydrogeology has been assessed through the integration of hydrogeophysics with hydrochemistry, hydrodynamics, and studies of vegetation response to water availability (using Landsat time-series analysis). The approach has also adapted deterministic and stochastic structural analysis approaches developed for use with seismic reflection data in the oil industry, to analyse AEM datasets. This inter-disciplinary approach has revealed complex fault zone conduit-barrier system behaviour that determines lateral and vertical groundwater flow, inter-aquifer leakage and localised recharge and discharge. This approach has revealed that Neogene deformation is a 'keystone element' of the Lower Darling floodplain and other surface hydrological and groundwater systems in Australia.
INTRODUCTION The application of any tool or technique depends on the scale and issues one is trying to resolve. In the extensive landscapes of Australia variation in sedimentary environments, depth of weathering and weathering processes have combined to produce a regolith layer that is thick and complex, especially in the low lying areas. Conventional surveys such as soil and surface hydrology are used to define surface regolith-landscape models and the hydrology of the vadose zone, and provide valuable information for various purposes, e.g. agriculture and engineering. However, these models fall short of postulating the three dimensional (3D) distributions of regolith materials at depth and their attributes, such as sedimentary facies and base of weathering. Data from water bores and other drilling can be utilised but are only able to provide a generalised conceptual model except in local areas with high drilling density. Hence, other remotely sensed datasets, e.g. airborne geophysics, are required to fill in the data gap in regolith-dominated terrain.
Over the past decade, a relatively rich record of neotectonics has been revealed in continental Australia, however very few investigations into the hydrogeological implications have been undertaken. While the most active intra-plate deformation zones are readily identified by seismicity monitoring and satellite and airborne terrain mapping, advances in airborne electromagnetic (AEM) technology and data optimization have made it possible to map numerous, more subtle ‘blind’ intra-plate fault systems concealed in near-surface floodplain landscapes. To date, fault geometries, displacements, and fault zone properties remain ambiguous due to the combination of AEM footprint resolution, the non-uniqueness of the conductivity models and derived hydrostratigraphy and fault geometry solutions produced by AEM equivalent inversion models, and the inherent uncertainty of stitched 1D AEM inversion models. The resultant uncertainty in fault zone characterisation inhibits investigations into the permeability heterogeneity and anisotropy introduced by these faults, making it difficult to resolve the significance of these structures for groundwater processes.In this study, a novel, inter-disciplinary approach has been developed that helps characterise the hydrogeology of one such intra-plate fault zone in unconsolidated, near-surface floodplain sediments. The approach integrates the mapping of tectonic geomorphology, with mapping of sub-surface hydrostratigraphy and ‘blind’ intra-plate fault systems using AEM. Validation of fault zone geometry and displacement at local scales is provided by ground geophysics (e.g. seismic reflection, resistivity and surface nuclear magnetic resonance (SNMR)) and drilling. Fault zone hydrogeology, including permeability variability, has been assessed through the integration of geophysics with hydrochemistry, hydrodynamics, and studies of vegetation response to water availability (using Landsat time-series analysis). A combination of deterministic and stochastic approaches is then used to unravel complex fault zone conduit-barrier system behaviour that determines lateral and vertical groundwater flow, inter-aquifer leakage and recharge. This inter-disciplinary methodology has been used to parameterise numerical groundwater flow models and target potential groundwater resources.
This paper aims to establish the relationships between the electrical conductivity (EC) and the various physical attributes of regolith materials, i.e. water content, salinity of the pore fluids and<br>textures, that allow the use of EC values to identify and map the desired geological units, namely the Blanchetown Clay and the higher transmissive coarse-grained sediments of the Loxton-Parilla Sands of the Murray Basin. It also illustrates the use of airborne electromagnetic (AEM) and ground data, in deriving customized products for managing the salinity issues associated with the Murray River in the Riverland region of South Australia. The two main derived products are maps showing the distribution and thickness of the Blanchetown Clay, and the Pliocene regression strand patterns.
New high-resolution airborne geophysical data acquired in the Broken Hill Region are being used to assess the deformational history and define the regional structural regime. The interpretation of these data may enable new structural and stratigraphic models to be postulated that will enhance and revitalise the exploration thrust within the Broken Hill Region.
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