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Visualizing structures An introduction to the geometry of geological structures in the field.

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Presentation on theme: "Visualizing structures An introduction to the geometry of geological structures in the field."— Presentation transcript:

1 Visualizing structures An introduction to the geometry of geological structures in the field

2 Goals To familiarize you with the 3- dimensionality of geological structures in the field Provide you with simple rules to use in geologic mapping of structures

3 3D spaces to deal with Topographic Depositional/intrusive Deformational They all intersect

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7 Shaded Non-shaded

8 Any structures will intersect an irregular topography Try picturing how will a horizontal layer cut this relief

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10 Horizontal plane - follows topo contours

11 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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17 Complicating the issue a little bit… Unconformity, what is it?

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20 Possible scenario: Deposition, erosion, deformation, new deposition

21 The way this would look in a canyon near Page, AZ

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23 Igneous intrusions

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25 Structures on block diagrams

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29 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.

30 The simplest scenario: a horizontal bed

31 Horizontal beds (a’la water line)

32 Some shallow tilt of a plane

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36 Rule of v’s

37 An example

38 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.

39 Tucson Mts.

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42 Cross-sections

43 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!


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