To portray or infer depth to crystalline basement in South Australia

To portray or infer depth to crystalline basement in South Australia

Source data include information submitted by mineral and petroleum exploration companies as part of statutory reporting requirements, information from academic institutions, and information collected by Department for Energy and Mining (DEM) and...

Source data include information submitted by mineral and petroleum exploration companies as part of statutory reporting requirements, information from academic institutions, and information collected by Department for Energy and Mining (DEM) and its predecessors. Hardcopy data were transcribed manually into SA_GEODATA or manually via project databases which were later uploaded. Data received in digital form were checked and corrected as necessary before upload into SA_GEODATA. Source history: Locational coordinates and The data is updated in SARIG on a daily basis.

The top of crystalline basement for the Gawler Province includes Mesoproterozoic and older rocks affected by the Mesoproterozoic Kararan Orogeny and older events; on current interpretations this definition includes the Itiledoo Basin (Blue Range Beds) but excludes the Cariewerloo Basin (Pandurra Formation). The eastern and southeastern margins of the area are placed along the eastern edges of the Torrens Hinge Zone and Stuart and Spencer Shelves, and along the Kangaroo Island Shear Zone. The above-named included areas are essentially unaffected by the Delamerian Orogeny.

The top of crystalline basement for the Musgrave Province includes Mesoproterozoic and older rocks affected by the Mesoproterozoic Musgravian Orogeny and any older events. This definition includes Neoproterozoic mafic dykes which cannot be separated and excluded reliably on present information. The southern margin of the area is placed along the thrust-faulted contact with the Neoproterozoic-Devonian Officer Basin (except in areas where geophysical data show Musgrave Province rocks extending below the basin). The eastern margin, which is overlain by a series of stacked Neoproterozoic to Mesozoic basins, is placed at the furthest extent of geophysical response.

The top of crystalline basement for the Officer Basin, basement is defined as inferred pre-(?Mesoproterozoic) basement to the Neoproterozoic to Devonian Officer Basin. Significant effects of the Neoproterozoic-Cambrian Petermann, Cambrian-Ordovician Delamerian and Devonian-Carboniferous Alice Springs Orogenies are confined to the northeast corner and are disregarded.

The top of crystalline basement for the cratonic central region of the Curnamona Province includes Mesoproterozoic and older rocks affected by the Palaeo-Mesoproterozoic Olarian Orogeny and older events but without evidence of significant Delamerian Orogeny influence. Included also are basic volcanics and sediments (in part Cariewerloo Basin equivalent?) of the Benagerie Ridge.

The top of crystalline basement for the Coompana Block, is defined as the top of all rocks older than the Permian Denman Basin: this definition encompasses basic volcanics and sediments possibly as young as Cambrian, basic plugs and dykes of unknown age (possibly equivalent to Mesoproterozoic Giles Complex), and gneiss with possible Musgravian Orogeny influence (Mallabie 1).

In the eastern portion of SA, where Ordovician and older rocks are affected by the Cambrian-Ordovician Delamerian Orogeny and older events, crystalline basement includes the Adelaide Geosyncline, Kanmantoo Province and basement to the Murray Basin. This latter affected area excludes the cratonic region of the Curnamona Province. In the Warburton Basin, Cambro-Ordovican sediments are included, despite minimal evidence of Delamerian influence, as basement to these rocks has only been encountered in a few drillholes and may not be detectable with geophysics.

The Cover thickness grid is indicative of cover thickness over South Australia, interpolated from the combined inputs of drillhole stratigraphy, drillhole lithology, seismic basement picks and EM basement picks.  The ESRI Natural Neighbours interpolator was used throughout the gridding process.  The processing methodology was Supervised Variable Density (Katona, 2016) which iteratively gridded the data at progressively finer resolution, starting at 12,800m and ending at 400m.  
To ensure the interpolator honoured sparse drillhole points, selected points used during the 12,800m and 6,400m iterations of gridding were weighted higher by duplicating these points and snapping the duplicates to the nearest cell centroids, thus ensuring that the final grid values would better fit to the input point data.

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