USING AIRBORNE ELECTROMAGNETICS TO MAP NEOTECTONICS IN UNCONSOLIDATED ALLUVIAL SEDIMENTS: A CASE STUDY FROM THE RIVER DARLING FLOODPLAIN, WESTERN NSW, AUSTRALIA

PreviousNext You have accessSymposium on the Application of Geophysics to Engineering and Environmental Problems 2013USING AIRBORNE ELECTROMAGNETICS TO MAP NEOTECTONICS IN UNCONSOLIDATED ALLUVIAL SEDIMENTS: A CASE STUDY FROM THE RIVER DARLING FLOODPLAIN, WESTERN NSW, AUSTRALIAAuthors: Ken LawrieDavid GibsonLarysa HalasNiels B ChristensenRoss S BrodieKen Lawrie Geoscience Australia;Search for more papers by this author, David Gibson Geoscience Australia;Search for more papers by this author, Larysa Halas Geoscience Australia;Search for more papers by this author, Niels B Christensen Aarhus UniversitySearch for more papers by this author, and Ross S Brodie Geoscience Australia;Search for more papers by this authorhttps://doi.org/10.4133/sageep2013-193.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract In this study, airborne electromagnetics (AEM), high resolution LiDAR, and drilling (100 bores) were acquired to map and assess groundwater resources and managed aquifer recharge options in the River Darling Floodplain. Neotectonic faulting and uplift has previously been described along the north-western margin of the Murray Basin along the adjacent Darling Lineament, however no evidence of neotectonics had previously been identified in the study area. Initial inversions of the AEM data revealed a multi-layered conductivity structure broadly consistent with the hydrostratigraphy identified in drilling. However, initial laterally and spatially constrained inversions showed only moderate correlations with ground data in the near-surface (∼20m). As additional information from drilling and ground and borehole geophysical surveys became available, various horizontal and vertical constraints were trialled using a new Wave Number Domain Approximate Inversion procedure with a 1D multi-layer model and constraints in 3D. The resultant 3D conductivity model revealed that an important Pleistocene aquitard (Blanchetown Clay) confining the main aquifer of interest (Calivil Formation), has an undulating surface, which is locally sharply offset. An interpreted top surface suggests that it has been affected by significant warping and faulting, as well as regional tilting due to basin subsidence or margin uplift. Overall, the top surface of the Blanchetown Clay varies in elevation by 60m. Many of the sharp offsets in the conductivity layers are coincident with lineaments observed in the LiDAR data, and with underlying basement faults mapped from airborne magnetic data. The identification of neotectonics in this area was made possible through the acquisition of high resolution AEM data, and the selection of appropriate horizontal and vertical constraints in inversion procedures. Recognition of faulting in the unconsolidated sedimentary sequence helps explain the rapid recharge of underlying Pliocene aquifers, with neotectonics recognised as a key component of the hydrogeological conceptual model. Permalink: https://doi.org/10.4133/sageep2013-193.1FiguresReferencesRelatedDetails Symposium on the Application of Geophysics to Engineering and Environmental Problems 2013ISSN (online):1554-8015Copyright: 2013 Pages: 821 publication data© 2013 Published in electronic format with permission by the Environment and Engineering Geophysical SocietyPublisher:Environmental & Engineering Geophysical Society HistoryPublished: 28 May 2013 CITATION INFORMATION Ken Lawrie, David Gibson, Larysa Halas, Niels B Christensen, and Ross S Brodie, (2013), "USING AIRBORNE ELECTROMAGNETICS TO MAP NEOTECTONICS IN UNCONSOLIDATED ALLUVIAL SEDIMENTS: A CASE STUDY FROM THE RIVER DARLING FLOODPLAIN, WESTERN NSW, AUSTRALIA," Symposium on the Application of Geophysics to Engineering and Environmental Problems Proceedings : 659-659. https://doi.org/10.4133/sageep2013-193.1 Plain-Language Summary PDF DownloadLoading ...