Mawson Escarpment Geology GIS Dataset

Full description

There are several ArcInfo coverages described by this metadata record - FRAME, GEOL, MAPGRID, SITES, STRLINE and STRUC (in that order). Each coverage is described below. The data is also provided as shapefiles and ArcInfo interchange files.
The data was used for the Mawson Escarpment Geology map published in 1998. This map is available from a URL provided in this metadata record.

FRAME:

The coverage FRAME contains (arcs) and (polygon, label) and forms the limits of the data sets or map coverage of the MAWSON ESCARPMENT area of the AUSTRALIAN ANTARCTIC TERRITORY.

The purpose or intentions for this dataset is to form a cookie cutter for future data which may be aquired and require clipping to the map/data area.

GEOL:

The coverage GEOL is historical geological data covering the MAWSON ESCARPMENT area.

The data were captured in ARC/INFO format and combined with geological outcrops that were accurately digitised over a March 1989 Landsat Thematic Mapper image at a scale of 1:100000.
It is not recomended that this data be used beyond this scale.

The coverage contains Arcs (lines) and polygons (polygon labels). These object are attributed as fully as possible in their .aat file for arcs and .pat for polygon labels and conform with the Geoscience Australia Geoscience Data Dictionary Version 98.04

The purpose or intentions for the dataset is that it become part of a greater geological database of the Australian Antarctic Territory.

(1998-04-10 - 1998-06-30)

MAPGRID:

MAPGRID is a graticule that was generated as a 5 minute by 5 minute grid mainly to allow for good location/registration of source materials for digitising and adding some locational anno.mapgrat

This covers other function was to be used for a proof plot.

(1998-04-22 - 1998-06-30)

SITES:

The purpose or intentions for this dataset is to provide the approximate location of this historic data on sample sites in the MAWSON ESCARPMENT region of the AUSTRALIAN ANTARCTIC TERRITORY, for future expansion or more accurate positioning when improved records of location are found.

(1998-05-11 - 1998-06-30)

STRLINE:

This Structural lines for geology coverage is named (STRLINE).

The purpose or intentions for the dataset is to have the linear structural features in their own coverage containing only structure which does not form polygon boundaries.

(1998-05-28 - 1998-06-30)

STRUC:

This coverage called STRUC for structural measurements is a point coverage. It can be described as Mesoscopic structures at a site or outcrop.

The purpose or intentions for the dataset is to provide all the known structural point data information in the one coverage.

(1998-05-28 - 1998-06-30)

Lineage

Progress Code: completed

Statement: FRAME: The coverage FRAME was generated from within the ARC/INFO environment. Used fishnet and generate box to define parameters for area to be covered, arcs densified by stipulating vertex (0.001), project cover ll_box frame_3 ll_wgs84_42UTM.prj Renamed to FRAME and attributed in ARCEDIT to conform with Geoscience Australia GEOSCIENCE DATA DICTIONARY version 98.04 GEOL: This geological data were obtained by merging infomation from several different historical sources. A March 1989 Landsat UTM 1:100000 image map was reprocessed to reduce shadow effect and allow for better outcrop definition. (Zone 42, WGS84 horizontal datum and a magnetic variation of 73 degrees west for 1985 and moving westerly by 0.1 degrees each year) This image was then used as base for the interpretation of geological outcrops which were then manually digitised at 1:100000 in spatially located igds format. The resultant .dgn file was imported into ARC/INFO format and outcrop areas edited on screen while superimposed over the digital image map at approximately 1:60000 for greater accuracy. Other source material used to determine the geology within the digitised outcrops were :- Geology of the Southern Prince Charles Mountains (1982) 1:500000 was used to define the lithological breakup and descriptions for the Geology of Mawson Escarpment 1:100000, on the advise of R. J. Tingey (Ex Geoscience Australia) as being far more accurate than the Mawson Escarpment North and South 1:250000 (1975 preliminary maps). These maps were scanned, vectorised in IGDS format and reprojected to the parameters of the digital image and imported into ARC/INFO but not used due to original maps having been distorted to fit the controls in use at that time. It was decided to have the internal geology manually recompiled using a local outcrop, best-fit method at 1:100000 including the placement of symbols. It should therefore be noted that accuracy of internal geological boundaries and dykes could be out by 200 metres in some cases. This compilation was digitised in ARC/INFO and appended to the GEOL coverage. The GEOL coverage was edited and attributed in ARCEDIT, to conform with the Geoscience Australia GEOSCIENCE DATA DICTIONARY Version 98.04 The Data Dictionary normally only allows a 254 character LITH_DESC field of the geol.pat file but two extra fields LITH_DESC2 and LITH_DESC3 have been added to fully describe the lithology. The coverage was built for LINES and POLYGONS, then CREATELABELS command used to label each polygon area and checked for label errors. The .pat file was then attributed to reflect the map_symb and any lithological information based on the Geology of the Southern Prince Charles Mountains (1982) 1:500000. MAPGRID: The coverage MAPGRID is a standard coverage name when related to the Geoscience Australia GEOSCIENCE DATA DICTONARY. Annotation (anno.mapgrat) is attached to this coverage to provide the user with latitude/longitude values for the arcs. The user may however not get the degree symbol to display as textset was geol.text This cover is provided as it may be useful as a backcover for location over landsat image data or for plotting purposes. SITES: The SITES coverage is a point cover depicting Geoscience Australia sample localities/sites in the MAWSON ESCARPMENT area of the AUSTRALIAN ANTARCTIC TERRITORY. These sites are regional and have been located by position on recognisable features with the resultant accuracy being moderate to poor,(ie within 500m). Without GPS or other coordinants being avaliable historic map bases were used (1973). At most of these sample locations many samples are located a the one point, so to select by box would be the best method of interigation of these slightly offset labels. They have not been snapped to a single point as it is uncertain that they were taken from the same point. STRLINE: Name - STRLINE is the coverage that contains any folds, joints, linier and trends. The structural data in this cover was obtained from historical sources namely old 1973 and 1982 maps. The information was enlarged to a scale of 1:10000 and manually recompiled over a landsat image, then digitised and brought into this coverage and attributed. The accuracy of this data are not considered to be to high but does reflect the historic data as well as possible. STRUC: Source material - the structural symbology in this dataset has been drived from historic maps. The 1982 Geology of the Southern Prince Charles Mountains at 1:500000 was deemed more reliable By R. J.Tingey (ex Geoscience Australia) than the two 1:250000 1973 geological maps covering the area. The structural symbols ie strike and dip of foliation etc have been place with azimuth being manually calculated clockwise from grid north which appears to have positioned them as on the origional map when rot_angle calculated to equal 360 - the azimuth. They would have been totally different to the maps if magnetic north were used. (ie 73 degrees west in 1995 plus 0.1 per year) The label points for the structural symbology were then attributed to conform with the Geoscience Australia Geoscience Data Dictionary version 98.04 and details entered where known.