WATER WARS: A look at Gallatin Valley Water Controversies





Stop 5:
Day Ranch

Stop 6:
Fish Creek


Stop 7:
Other Considerations


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Stop 4. A rolling look at rocks:
the unconformity

At this stop we will continue to explore the idea of paleotopography and tectonic uplift in the Valley.

Goals:

  1. Continue to explore how the rock units evolved into what we see today.
  2. Determine what the rock units might look like below the surface.


for Air Photo
Stop 4 topographic portion To better orient yourself, take a look at the trip log page!
contour interval: 40 ft

The Archean-Tertiary Unconformity:


Looking south on River Road

The River Road is covering the unconformity between the Achaean gneiss and Tertiary sediments. Understanding why we see this unconformity and it's landscape is very important to the controversy. You might notice that we have not changed elevation significantly, yet the gneiss is topographically lower here than in stop 2. This indicates one of two possibilities,
1. the gneiss is moved by tectonic processes (i.e. faulted), or...
2. the surface of the gneiss has paleotopography.

Because geologists don't have x-ray vision and can not see rock units in the subsurface, they must use different type data to evaluate subsurface geology. They will often use several remote sensing techniques, yet that data does not give an absolute answer as to what is in the subsurface. Well (both oil and water) data is a very reliable method of determining subsurface geology (as long as you have enough data to piece together a good subsurface profile!).
Tasks!
  • Look at the well data. Does this give you an idea of what the gneiss might look like in the subsurface? Sketch the subsurface profile of the crystalline rock (do the best you can!).

Now that we have explored the geology of the area, move on to stop 5 and begin to link our geologic knowledge to the controversy.

 

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