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In this case, some of the rock layers were tilted and eroded after they
were laid down flat, then other rock layers were deposited on top of them,
making an angular unconformity. However, we have no way of knowing how much
time elapsed or how many rock layers were eroded before the current structure
was developed. You needed to be sure to say that. Here's my history:
You could argue for a last stage, where the rocks all get raised up so that
our road cut or canyon or whatever exposes the rocks, but that's not necessary
for this assignment.
- Layers D, E, F, G, and H were laid down in that order.
- Sometime after deposition of H, the rocks were tilted.
- Probably at the same time, they were uplifted, and erosion
- After they were eroded to a flat surface, the rock layers
subsided to a level where more deposition could occur.
- After an unknown amount of time, layer C was laid down.
Here there is an angular unconformity, and we have
no way of knowing how much absolute time is missing.
- Next, layer B was laid down.
- Finally, layer A was laid down.
Tue Mar 11 18:16:04 PST 1997