Authors / CoAuthors
Clarke, J. | Lawrie, K. | Tan, K.P. | Gibson, D. | Halas, L.
Abstract
A multi-disciplinary systems mapping approach, utilising airborne electromagnetics (AEM), and validated by a 7.5 km drilling program (100 sonic and rotary mud holes), and complementary hydrogeological and hydrogeochemical investigations, has identified potential groundwater resources stored within Pliocene aquifers (Calivil Formation (CFm) and Loxton Parilla Sands (LPS)) to depths of ~100m beneath the Darling River floodplain. The Pliocene aquifers are sandwiched between thick clay aquitards, and vary from confined to 'leaky confined' systems. The CFm, which extends over the north and central parts of the study area, varies significantly in thickness (0-70 m). This variability results from (1) in-filling of broad (structurally-controlled) palaeovalleys in an undulating palaeo-landscape, with relief of up to 40m from valley bottoms to hill tops; and (2) post-depositional tectonic effects that include structural inversion on faults, as well as warping and tilting. The lower bounding surface of the CFm is marked by an erosional contact (10 m year hiatus) with Renmark Group sediments. Facies analysis indicates that the CFm was deposited in deep braided streams across a dissected sedimentary landscape. Overall, the sequence is fining-upwards, with evidence for transgression over the LPS. Channel fill materials comprise gravels and sands, and local fine-grained units represent abandoned channels and local floodplain sediments. The upper surface of the CFm is irregular, with up to 16 m of relief evident, due to a combination of tectonics and depositional filling of channel and bar topography in the upper CFm. Integration of textural and hydraulic testing data has revealed there are five hydraulic classes within the CFm, ranging from clays to gravels. At a regional scale (kms), sands and gravels are widely distributed with particularly good aquifers developed in palaeochannels and at the confluence of palaeo-river systems. In these strategic locations, the CFm has high storage capacity, very high transmissivities (up to 50 l/s), and significant volumes of fresh groundwater. At a local scale, there is considerable lithological heterogeneity (10s to 100s of metres) within the palaeochannels. The use of AEM was critical to the targeting of premium aquifer sites and detailed hydrogeological investigations.
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nonGeographicDataset
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75729
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- External PublicationAbstract
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Geology
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2013-01-01T00:00:00
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Abstract prepared for submission to the International Association of Hydrogeologists (IAH).
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