Transcript Visualizing structures

Visualizing structures
An introduction to the geometry of
geological structures in the field
Goals
• To familiarize you with the 3dimensionality of geological structures in
the field
• Provide you with simple rules to use in
geologic mapping of structures
3D spaces to deal with
• Topographic
• Depositional/intrusive
• Deformational
They all intersect
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Non-shaded
Shaded
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Any structures will intersect an irregular topography
Try picturing how will a horizontal layer cut this relief
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Horizontal plane - follows topo contours
• Let us now put the real topography aside
and step into the realm of “primary”
geologic structures - layering of
sedimentary units, intrusions, viewed in
an idealized 3D framework
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Complicating the issue a little bit…
Unconformity, what is it?
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Possible scenario:
Deposition, erosion, deformation, new deposition
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The way this would look in a canyon near Page, AZ
Igneous intrusions
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Structures on block diagrams
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• Let us know try to drape structures onto
topography and come up with some simple
rules for the way they will plot on maps.
To keep things simple for now, I will deal mainly
with planes and not with lines.
So what can a plane be? A bed, a fault, a dike, a
sill an unconformity, anything that is planar.
The simplest scenario: a horizontal bed
Horizontal beds (a’la water line)
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Some shallow tilt of a plane
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Rule of v’s
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An example
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• So then what is a geological map?
An overlay of geologic structures (e.g. like
the planes shown here on the 2D
topographic map). Let’s take a look.
Tucson Mts.
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Cross-sections
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Remember
• The 3 spaces you deal with: topo,
primary structures and deformational
(secondary) structures);
• Rule of v’s, overall topography/structure
intersections of any planes
• A structure looks very different
depending from where you look at it!
A preview of Cottonwood
Be familiar with this lecture and this week’s lab it will be important for Saturday’s exercise.