Browsing by Author "Sundaram, B"

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    Hydrochemical and isotopic fingerprinting of the Walloon coal measures and adjacant aquifiers in the Clarence-Moreton and Eastern Basins in Southeast Queensland
    (Geological Society of Australia, 2014-07-07) Raiber, M; Cendón, DI; Feitz, A; Sundaram, B; Suckow, A
    The Clarence-Moreton Basin in New South Wales and Queensland is one of six nationwide priority regions where the potential impacts of future coal seam gas extractions and coal mining on water-dependent assets are being assessed through a national programme of Bioregional Assessments. The Clarence-Moreton Basin is an elongated intracratonic sag basin that contains sedimentary sequences of Middle and Late Triassic to Lower Cretaceous age with a combined thickness of up to approximately 3500 to 4000 m. Overlying the basin sedimentary sequences within the Clarence-Moreton bioregion (the eastwards draining part of the basin) are five major catchment systems (Lockyer Valley, Bremer/Warrill, Logan/Albert in Queensland, and the Richmond and Clarence river catchments in NSW), which host important alluvial groundwater and surface water resources that are intensively used for irrigation. In addition, these catchments host significant assets such as groundwater-dependant ecosystems (e.g. springs and wetlands). In order to predict the potential impacts of depressurisation associated with coal seam gas extraction from the Walloon Coal Measures (major target of CSG exploration in the Clarence-Moreton Basin), an accurate understanding of the links between different components of the hydrological system is essential. Prior to the development of numerical models, it is critical to describe potential connectivity pathways between deep and shallow aquifers, as well as interaction between groundwater and surface water. In order to assist with the development of reliable conceptual models that describe these interactions and constitute a road map to bioregional assessments, we have constructed a 3D geological model from elevation (DEM), stratigraphic, seismic and lithological data using GoCAD (Paradigm) 3D geological modelling software. The 3D geological model represents the major alluvial, sedimentary and volcanic aquifers and aquitards of the Clarence-Moreton bioregion. It helps to develop a more realistic understanding of the aquifer system behaviour, particularly if integrated with complementary data sources such as water level or hydrochemical data, and it will provide the geometric framework for the groundwater numerical model. The 3D geological model highlights the structural complexity of the Clarence-Moreton Basin, with significant vertical displacements of major basin units of several hundred meters registered along major regional fault systems, and abutments of stratigraphic units against basement ridges or pinching out of units observed in different parts of the basin. These observed structural features and the geometric characteristics of aquifers/aquitards can have a significant influence on potential connectivity pathways. For example, the thinning of the Gatton Sandstone against the underlying Woogaroo Subgroup at the basin margin in the Lockyer Valley results in upwards seepage of groundwater from the Gatton Sandstone into the alluvial aquifer, and this upwards discharge probably also feeds wetlands located along the northern margin of the Gatton Sandstone.