The Great Unconformity at the bottom of the grand canyon present even a more difficult case. The bottom layer consists of several different types of rock including intrusions. The upper layers are several thousands of feet thick and tens of miles long.
I've posted a cross section of that region at EvC more than once. From a YEC perspective I have hypothesized that the layers were all in place but not completely hardened when there was an intrusion of magma from below that displaced the lowest strata, upending them.
The volcanic force uplifted the whole column at the north of the Grand Canyon and was the cause of the crack in the layers that eventually became the canyon itself, after which water -- water left over from the flood, held in temporary lakes here and there -- eroded it over time, but relatively rapidly by evo standards, to its present breadth. There are also cracks to the north in the Grand Staircase that formed smaller canyons.
The layers did not crack or buckle over the mound to the north of the GC which was created by the uplifting force of the magma intrusion below. On the diagram they maintain their parallel form over the curve without breaking up. {Edit: This fact shows that they were all in place when the volcanic action underneath occurred. They could not have formed later as there is no way gravity would allow layers to form in parallel slowly over a mound.
My theory is that the weight of the upper layers relative to the force from below was enough to keep them from distorting in the same way as the lower layers, that is, they maintained their parallel form, while the force played out in the tilting and sliding of the lower layers beneath the weight of the upper column, at the division between two different sediments. The lower tilted and slid, but the upper were merely lifted. Quite an earthquake I would imagine. Similar processes could explain other unconformities. Sorry I can't access links until my computer problem is fixed, sometime next week.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
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Edited by Faith, : No reason given.
Edited by Faith, : No reason given.