Palaeochannels near West Wyalong, New South Wales: A case study in delineation and modelling using aeromagnetics

Mackey, T.; Lawrie, Ken; Wilkes, Paul; Munday, Tim; Kovacs, N.; Chan, R. A.; Gibson, D.; Chartres, Colin J.; Evans, Ray

doi:10.1071/eg00001

Cited by 14 publications

(8 citation statements)

References 2 publications

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“…The velocity differences involved are subtle, but the curved outline of the feature indicates it is not an artifact from acquisition geometry but is a true velocity anomaly produced by the subsurface geology. Moreover, it correlates with the predominant strike of the large paleodrainage feature interpreted from aerial magnetic surveys (Mackey et al, 2000). The orientation and depth of this anomaly correlate with Table 1.…”

Section: Tomographic Modelingmentioning

confidence: 68%

“…The presence of detrital ferruginous pisolith deposits with magnetic responses (Mackey et al, 2000) was confirmed by magnetic and airborne/ground EM surveys, along with drillhole data and recent landfill cuttings (Mackey et al, 2000) logged near the survey site. The pisoliths are located in lenses of gravel, which formed in paleochannel deposits in a northeast-southwest orientation at about 10 m depth in the seismic field area.…”

Section: Discussionmentioning

confidence: 96%

“…Most bedrock is covered by a Quaternary regolith, primarily sourced from paleodrainage deposits. Cuttings in the region (Mackey et al, 2000) and regolith drill data indicate the magnetic minerals within some paleochannel deposits may occur in discrete lenses of detrital magnetic ferruginous pisoliths, deposited in paleochannels incised into the regolith at approximately 10 m depth. Adjacent to the field site, the Yiddah Formation, a Silurian-Devonian sandstone, siltstone, and minor conglomerate formation, emerges as a low outcrop surrounded by a region of Quaternary colluvium and alluvium scree.…”

Section: Introductionmentioning

confidence: 99%

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3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia

Deen

Gohl

2002

GEOPHYSICS

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Buried paleochannels are of significant interest for understanding hydrological mechanisms and their potential as alluvial gold deposits. Seismic tomographic methods are a suitable solution for resolving the vertical and horizontal structure of such features. We assess a method for seismic 3-D tomographic inversion from refraction arrivals with reflection control over a suspected paleochannel adjacent to the Wyalong gold fields in the Lachlan fold belt of central New South Wales, Australia. A standard multichannel engineering seismic recording and cable-receiver system was used on a 3-D field geometry of multiple linear arrays. More than 3000 P-wave first-arrival traveltime values were inverted using a regularized inversion scheme for which simplified 2-D models served as initial velocity-depth models for the complete 3-D inversion. Seismic reflection arrivals provided additional depth estimates to the bedrock and compensated for a lack of refraction phases at that depth. Correlating the 3-D seismic velocity-depth data with existing drillhole and nonseismic geophysical data resulted in a detailed structural and compositional interpretation of the paleochannel and the incised regolith. The model suggests the presence of a system of deposits from meandering channels overlying a metasedimentary bedrock formation. The general paleodrainage deposit is relatively conductive in electromagnetic surveys, indicating a potential saline storage or transport mechanism.

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Section: Tomographic Modelingmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia

Deen

Gohl

2002

GEOPHYSICS

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“…This geological signal relates particularly to nearsurface units, which typically exist in smaller structures, and have weaker magnetizations and lower volumes than the bedrock units which provide most of the signal for the regional magnetic surveys. The value of detailed aeromagnetics in mapping palaeochannels has already been established (for example, Mackey et al, 2000). In this study we investigate aeromagnetic surveys flown to map near-surface deposits in the alluvial gold field of Teetulpa, in central South Australia.…”

Section: Introductionmentioning

confidence: 99%

Magnetic mapping of river channel and palaeochannel deposits - an example from Teetulpa, South Australia

Foss

Reed²,

Keeping³

et al. 2015

ASEG Extended Abstracts

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“…Copious amounts of significant geologic information such as structure, lithology, alteration, regolith/overburden and sedimentary processes, among other factors are deduced (Luyendyk, 1997;Milligan and Gunn, 1997;Gunn et al, 1997;Mackey et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Basement Classification through Enhanced Magnetic Data Reductions in parts of Ekiti State, Southwestern Nigeria

Akingboye

Ogunyele

2017

IJAG

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Enhanced magnetic data reductions via the use of various forms of filters were employed for basement classification in parts of Ekiti State. The data reductions and enhancement involve: reduction to equator (RTE), regional and residual, automatic gain control (AGC), downward continuation, upward continuations (1, 2, and 3 km), analytic signal (AS) and horizontal gradient (HG) to map and delineate basement rocks and structures, while surface relief and spectral plot were used to determine depth to top of magnetic sources. The images revealed that the study area is characterized by different lithologies. The rocks evinced lineaments and faults trending NE-SW (G-G', H-H', J-J', K-K'), NNE-SSW, E-W (minor) and approximately N-S, while the dykes are in NW-SE, NNW-SSW directions. The analytic signal (AS) and horizontal gradient (HG) revealed high amplitude reversed Z-like shape as migmatite rocks, differentiating them from the two flanks with low amplitude signals as schist and quartzite schist of Ijero and Aramoko and the granitic intrusive within these migmatised rocks around Ijan, Gbonyin and Ise/Otun. The shaded relief and the spectral plot showed that the total depth to top of magnetic sources ranged from 20m to 1.8km for shallower and deeper sources respectively.

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Palaeochannels near West Wyalong, New South Wales: A case study in delineation and modelling using aeromagnetics

Cited by 14 publications

References 2 publications

3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia

3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia

Magnetic mapping of river channel and palaeochannel deposits - an example from Teetulpa, South Australia

Basement Classification through Enhanced Magnetic Data Reductions in parts of Ekiti State, Southwestern Nigeria

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