Global Tectonics Lab
Geophysical Maps of Australia
The goal of this lab is to introduce you to some of the geophysical data sets that can be used to
interpret regional geology and tectonics. Of the many types of data available, the most useful
at a regional scale are gravity and magnetic data. These generally reflect the properties of
crystalline basement rocks, and therefore can be used to see “through” shallow sedimentary
cover to the fundamental structure below. Australian geologists and geological surveys have
been at the forefront of efforts to collect and disseminate these types of data, and we will use
recent compilations of data for the Australian continent in this lab.
Attached is a very brief introduction to how gravity and magnetic data are collected, and what
they are measuring. For detailed analysis and interpretation it is important to understand much
more, but for an initial interpretation and identification of critical relationships one can often
simply look at the patterns displayed in the data.
As is usual for our labs, the questions below are provided to give you some direction and a
product to turn in, but the real goal is for you to examine, and thoughtfully investigate, these
very different pictures of the geology of a region.
There are three maps (= data sets) for you to examine and compare: Geology of Australia,
Magnetic Anomaly Map of Australia, and Gravity Anomaly Map of Australia. In addition
there will be topographic (digital elevation) and satellite image maps that you may wish to
consult.
To Do
1. Spend some time simply looking at and comparing these three quite different ways of
looking at the geology and rock properties of the Australian continent. There are many
fascinating structures and fabrics (textures) that are visible in these data sets. Some are
clearly correlated with each other, and with surface geology and topography, the origin
and meaning of others is obscure.
a) Describe what you see in each of these maps. Discuss the major regions and
boundaries zones on each. Speculate about what these regions and boundary zones
may represent.
b) Compare the three maps. Note which regions and boundaries appear to correlate
among the three data sets, and which do not. What is most useful about each data set,
and how would you use each data set to interpret the regional geology?
c) One of the main purposes of geophysical data is to allow interpretation of
basement geology obscured by younger sedimentary cover. Are there places where
you can do this using these data sets? Describe one or two specific examples, and
your interpretation.
2. Choose two areas that seem especially interesting to you. Using tracing paper, draw the
major features of each data set. Overlay and compare the data. Analyze, interpret, and
discuss what you observe, and speculate about its origin and significance.