Mount Isa Inlier 1:100 000 geology: lithostratigraphy and chronostratigraphy

Brief description

These data are a digital representation of information depicted on the printed maps of Seigal, Hedleys Creek, Carrara Range Region, Lawn Hill Region, Riversleigh, Constance Range Region, Mount Oxide Region, Mammoth Mines Region, Myally, Alsace, Coolullah, Kennedy Gap, Prospector, Quamby, Mount Isa, Mary Kathleen, Marraba, Cloncurry, Oban, Duchess Region, Malbon, Kuridala Region, Selwyn Region, Dajarra and Ardmore 1:100 000 Geological Series and Mount Drummond 1:250 000 Geological Series produced by AGSO, the Geological Survey of Queensland (GSQ) and Northern Territory Geological Survey (NTGS). Data present include geological polygons (litho-stratigraphic units), linear structural features (faults, dykes, folds, trends, lineaments etc), and point features (mines, structural points etc). Polygons have a range of attributes extracted from each individual map including unit name, era, period and lithological description, while lines and points are feature coded according to the AGSO publication 'Symbols Used On Geological Maps' (BMR 1989). A standard look-up table of AGSO geological codes and associated descriptions is available (see ADDITIONAL METADATA). The data has gradually evolved from elementary CAD quality data into its present topologically structured GIS format, and hence has many imperfections and inconsistencies. Data has undergone rigorous validation and testing that includes over 80 different tests.

Lineage

Maintenance and Update Frequency: irregular

Statement: There are three steps relating to the initial data capture and upgrade to a high-level GIS: (i) Interpretation and creation of source maps; (ii) Data capture from source maps; (iii) Post-data capture upgrade. (i) Geological maps are a depiction of information acquired from interpretation (mostly aerial photography), field observation, and subsequent investigation (eg sample analysis for age and rock-type determination). Some detail may have been generalised, re-positioned, or omitted from the primary data for cartographic purposes. Maps were compiled from unrectified photo overlays onto topographic bases supplied by the Commonwealth mapping authorities. Drainage and, other topographic features (eg fence lines) were used for spatial control of the geological data. (ii) Data were captured from stable-base repromat used in the production of the hardcopy multi-colour geological maps. Initial acquisition was by high precision scanning. Resultant raster files were warped to fit digital graticules generated using Intergraph CAM software. Affine-1 warp was used, with the four corners of each tile forming tie points. Warped raster files were then vectorised and cleaned up using Abakos Provec and Scanfix software. Further interactive editing and additional capture of point data was carried out using MicroStation software. MicroStation vector data were plotted and visually checked. MicroStation vector data were translated to ArcInfo coverage format using in-house scripts and ESRIs IGDSARC utility. Attribute fields were populated using information from the printed maps and coverages were built for topology, checked and edited. (iii) The original data are imported from export files into double precision ArcInfo coverages. Spatial processing and transformations on the data were done using ESRI's ArcInfo (version 7.2.1) GIS software. See "More Metadata"