Reading a geological legend
Example taken from Maree 1:250 K sheet,
Geological Survey of South Australia
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Youngest rocks are placed at the top
Youngest rocks are placed at the top
A separate box of distinct colour or stipple is drawn for each rock type that can be distinguished on the basis of lithologyor age relationship (see super-position). The box should be placed in its appropriate geological era (vertical text) but they are not usually drawn to a scale.
A series of units of equivalent or indistinguishable age
(e.g. coeval plutons of distinct lithology) could be indicated by
several boxes arranged horizontally (not shown here).
A continuous series of units stacked vertically signifies
their relative age and conformable nature
Units drawn only partially across column indicates
that the units are not always present (discontinuous)
A break between a series of units signifies a time gap (disconformity)
Oldest rocks are placed at the bottom
Oldest rocks are placed at the bottom
A more complex example - mixed metamorphic and sedimentary rocks
A more complex example - mixed metamorphic and sedimentary rocks
Review the following example with schematic map, geological legend and a cartoon-style cross sections for parts of the Arunta Block, central Australia. The principles outlined for the Maree legend still apply. The Palaeoproterozoic metamorphic rocks of the Arunta Block are unconformably overlain and tectonically intercalated with Neoproterozoic rocks of the Amadeus Basin.
The example is taken from Altunga Harts Range Region 1:100K map, Northern Territory Geological Survey
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