Lawn Hill Platform and Leichhardt River Fault Trough measured stratigraphic section online GIS

Brief description

This GIS web browser contains stratigraphic information from the southern flank of the Murphy Inlier, Lawn Hill Platform and Leichhardt River Fault Trough in the Western Succession of the Mount Isa Block. The principal lithostratigraphic units covered by this dataset include the Surprise Creek Formation, Mount Isa and McNamara Groups. The images are pixilated versions of those contained on CD Records AGSO Record 1999/10, AGSO Record 1999/15, GA Record 2002/3. The data contained on the CD's is more comprehensive, at a better resolution and also contains cross sections that are not available over the web. No drill hole data is supplied in this viewer. The data compiled for this viewer was collected during the course of the NABRE, AMIRA P552 and pmd*CRC projects. The respective CD's also provide measured sections at different scales with slightly varying information available at 1:400, 1:1000, 1:2500 and 1:5000 scales. The information at each scale is slightly different. Plot files ready for printing also accompany the measured sections. Each of the measured sections contains primary observational data (grainsize, lithology, bed thickness, sedimentary structure and gamma ray curve) map-based lithostratigraphic units as shown on the 1:100,000 geological sheets, interpreted facies and sequence stratigraphic surfaces. Sections were measured using a Jacobs Staff and Abney Level and the rocks were marked in 1.5 m intervals of true thickness. Gamma ray data was collected at either 50 cm or 75 cm intervals of true thickness using hand-held Scintrex GRS 500 spectrometers that measured total gamma ray counts. A beryllium standard was used to calibrate each spectrometer. Each machine was calibrated at intervals of two to three hours. Each gamma reading was averaged over an interval of ten seconds. Outcrop discontinuities prevented the collection of stratigraphic data in a line of continuous section. As a result most of the sections present in this data set comprise a series of segments combined to form a single composite section. The single sections were all measured within a radius of several kilometres of each other. Individual sections were spliced together at prominent marker beds (outcrop tracing of strata), or by the use of overlapping gamma ray curves in conjunction with facies descriptions. Section locations shown in the web browser depict the base of each composite section. Grid coordinates for the base each composite section can be found in the header block of the appropriate section. The geological maps used in this web browser depict the approximate position of supersequence boundaries. Not all the geology for the region has been included and only the geology relevant to the measured sections has been used. The supersequences provided are based on the most appropriate lithostratigraphic boundaries and no new geological polygons have been created. It should be noted that the Torpedo Creek and Warrina Park Quartzites have been placed in the Prize Supersequence. However, we acknowledge that due to mis-mapping of these sand bodies the Torpedo Creek and Warrina Park Quartzites from the basal part of the Gun Supersequence at some locations.

Lineage

Maintenance and Update Frequency: unknown

Statement: GEOLOGY: 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. ROAD NETWORK (National Geoscience Dataset): This dataset (ANZCW0703002391) was compiled by Geoscience Australia staff from the original Digital Chart of the World VPF format dataset downloaded from the DCW website listed in the abstract. For information on the lineage of the original DCW (VPF format) datasets please view the Digital Chart of the World website listed in the abstract. The roads dataset was simplified so that only the towns relevant for the Online GIS were present. Post-DCW lineage The seperate DCW tiles NA11, UA11, QC32-33, QD31-33, QE31-33, QF31-33 and all the RC, RD, RE, RF, SC, SD, SE, SF, TC, TD, TE, TF, UC, UD, UE, UF, VC, VD, VE, VF, WC, WD, WE, WF, XC, XD, XE, XF, YC, YD, YE, YF, ZC, ZD, ZE and ZF were compiled into single covers based upon the separate DCW themes. The vegetation layer was not available for the Australian area. The data was then attributed fully as the existing coverages were attributed in code which only made sense with the DCW Data Dictionary. The field names were changed to be clearer for example the field AEPTVAl was changed to Elevation. No cleaning of the data was necessary exept for the place names coverages where upper and mixed case place names existed in the DCW data these were all changed to mixed case. Geoscience Australia compliant fields were added to the data at this stage: UFI and FEATURE with AGSO_CODE and DESC added to non-polygon themes. This dataset is a subset of the transport coverage which was compiled from the original DCW railroad arc coverage, the road arc coverages, the transportation structure line coverage, the transportation structure point coverage and the aeronautical point coverage. POPULATION CENTRES (National Geoscience Dataset): The population centres dataset (ANZCW0703002389) was simplified so that only the towns relevant for the Online GIS were present. See "More Metadata"