contact Cover

 

Northern Hemisphere Edition


Page Structure

Each page of the atlas consists of a table made up of a number of rows and columns of images, generally one row per geological model, with each column showing one type of representation:

 

Each cell in the table provides an active link to at least one file that may be loaded into a helper application (see next section for details). The table below explains what links are avaiable for each column type:
 
Link

Loads Noddy with history file

Loads FracViewer animation with block model 

Loads Geology Model as VRML file

Loads Wavelet Transform Model as VRML file

Block

LOAD JPEG IMAGE of geological model into browser

Gravity

Load gravity data into Noddy

-

Load gravity image as jpeg file

Magnetics

Load magnetics data into Noddy

-

Load magnetics image as jpeg file

Magnetics

Load magnetics data into Noddy

-

Load magnetics image as jpeg file

Magnetics at Pole

Load magnetics at pole data into Noddy

-

Load magnetics image as jpeg file

Magnetics at Pole 1VD

Load magnetics at pole first vertical derivative data into Noddy

-

Load magnetics image as jpeg file

Table showing the effects of clicking on an image from each column
Dynamic Links to Noddy

To get your computer to load the appropriate files into Noddy dynamically you obviously need those this programs (see links at the bottom of this page), and you also need to set your browsers helper applications settings for various file types as shown in the table below. These settings can be set as you load in a file type for the first time.
 
File Suffix File Type Helper Application Mime Type
his Noddy History File Noddy x-application/his
mag Noddy magentics image Noddy x-application/mag
grv Noddy gravity image Noddy x-application/grv
avi Animation of wavelet transform model FracView video/avi
jpeg Noddy geophysics image in jpeg format xv (for example) image/jpeg
wrz "Gzipped" VRML model of wavelet transform model 3D Exploration (for example) x-world/x-vrml

UNIX On the UNIX platform you will also need to inform the program where to look for the licence and UID files by adding the following to your .cshrc file (changing the path as appropriate):

setenv  NODDY_HOME  /usr/local/noddy
setenv    UIDPATH   /usr/local/noddy/%U

PC On the PC platform you will also need to inform the program where to look for the licence  file by adding the following to your autoexec.bat file (changing the path as appropriate):

set NODDY_HOME=c:\winprgs\noddy
path=c:\winprgs\noddy

File Naming Conventions

The jpeg and gif files for each section are contained in a number of directories divided up according to calculation and display type, so that for example, pseudocolour and gray scale look up table displays of the same data are stored separately.

jpeg image file names are of the form model name+image type.jpeg (and similarly for gifs) where image type is generally one of the following:
 
 
gl geology image
gg gravity image , gray scale look up table raster image 
mg magnetic image calculated at an inclination of -50°, gray scale look up table raster image
mr magnetic image calculated at an inclination of -50°, rainbow look up table raster image
mc magnetic image calculated at an inclination of -50°, rainbow look up table  colour contour image 
mpr magnetic image calculated at the South Pole, rainbow look up table raster image 
mpc magnetic image calculated at the South Pole, rainbow look up table colour contour image 
mp1vdr magnetic image calculated at the South Pole, 1st vertical derivative, rainbow look up table raster image 
mp1vdc magnetic image calculated at the South  Pole, 1st vertical derivative, rainbow look up colour contour image

 The Noddy Modelling System

Clicking on this icon opens up Noddy with the appropriate history file, and clicking on the geophysics images loads up the appropriate geophysical data into Noddy. The Noddy modelling system has been developed jointly by Monash and the CSIRO within the Australian Geodynamics Cooperative Research Centre (with major funding through AMIRA). It is a kinematic forward-modelling system which builds up a three-dimensional geometry through the imposition of a sequence of deformation events on a initial stratigraphy, and then calculates the gravity and magnetic responses for this structure. Noddy is based on two types of algorithms, those that deal with forward modelling the geology, and those that deal with forward modelling the potential-field response. For the latest demo version, visit the Encom Web Site

Geological Modelling

The geological modelling is achieved by superimposing a series of deformations, described as parameterised displacement equations acting on an initial stratigraphy.

The choice of deformation "events" includes folding, faulting, unconformities, shear zones, dykes, plugs, homogeneous strains, tilts, and imported geometries: voxel (or Volume Element) models and some triangulated forms, and these events may be combined in any order in any number. The starting stratigraphy for the modelling is not only geological, but also represents a geophysical rock property stratigraphy, and this allows us to calculate sophisticated geophysical behaviour such as alteration zones around faults, where the susceptibilities are modified systematically as a function of distance away from the fault, and  also remanence vectors which are deflected around fold hinges.

Geophysical Modelling

The geophysical modelling is accomplished by dividing the final geological structure into voxels, and using a modification of Hjelt's dipping prism equations to calculate the potential-field response of the 3D volume (Hjelt, S.E. 1972. Magnetostatic anomalies of dipping prisms. Geoexploration, 10, 239-246. and Hjelt, S.E. 1974. The gravity anomaly of a dipping prism. Geoexploration, 12, 29-39.). We have also implemented a Fourier domain calculation of potential-field response, based on the same voxel model of the geology, and the results presented here make use of the most suitable scheme for a particular model geometry. Both gravity and magnetic models are calculated as airborne surveys, typically at an altitude of 80 m.

Geophysical Parameters

The c.g.s. unit system is used in this atlas, and magnetic calculations are either performed at the South Pole with a field strength of 70,000 gamma (or nT) or at an inclination of -50° with a field strength of 50,000 gamma. The magnetic declination is always set to 0, and North is up in all geophysical images. The magnetic images show the true anomalous component of the total field, and the gravity images show the vertical component of the field. In the key k is used as the symbol for magnetic susceptibility, and  for density .

Geophysical Image Display

The gravity and magnetic images in this atlas are displayed as either grayscale or pseudo-colour raster images, or pseudo-colour contour plots. In all cases the look up table is linear, and is in general clipped to the maximum and minimum range for the particular data set, which maximises the clarity of anomaly shapes. Where absolute anomaly intensities need to be viewed, profiles across the data or an absolute look up tables are applied, and these cases are noted in the text.

VRML Viewers

Clicking on these icons opens up a window with a VRML (Virtual Reality Meta Language) model in it. There are many different VRML Viewers available, and the availability of any one piece of software is not very stable, however at the time of production of this site 3D Exploration (PC only); Install Cortona VRML Client for FREE! Cortona VRML Browser Plugin (most Platforms) or VRML Viewer (PC Only) can be used. In order to reduce download times, all the VRML models are compressed using a package called gzip. (Most unzip utilities will be able to use uncompress this format). The Cortona Browser plugin is happy with this format.

AVI Viewers

Clicking on this icon opens up a window with a AVI format movie in it. There are many different AVI Viewers available, and the availability of any one piece of software is not very stable, however at the time of production of this site Quicktime (PC & MAC only) or MediaPlayer (PC Only) can be used.

Acknowledgements

I would like to acknowledge the contribution of Rick Valenta, whose idea this was, and who produced the first examples, some of which are included here. The Fractal Graphics team, and especially Darren Holden are thanked for all of their work in producing the wavelet transform models. I would also like to thank Maurice Craig, Paul Manser, Stewart Rodregues, Alla Geiro and George Jung who all worked on aspects of the Noddy code. Ian Neilson and Ian Brayshaw were invaluable in generating their help in generating the HTML code. Finally I would like to thank Joe Cuccuzza from AMIRA for his support during this project, and the many sponsors who helped fund it (Aberfoyle, Australian Geological Survey Organisation, BHP Co Ltd, GENCOR, CRA Exploration Pty Ltd, Department of Mines and Energy, South Australia (MESA), North Ltd, MIM Exploration Pty Ltd, Newcrest Mining Limited, Pasminco Exploration, RGC Exploration Pty Ltd, RTZ Ltd, Sumitomo Metal Mining Oceania, Western Mining Corporation Ltd). I would finally like to thank Dave Gamble for his careful review.


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All models created using Noddy
1998-2-23  Copyright © 1998-2002 AGCRC & Mark Jessell