A useful trick for keeping the effect of erosion on folds straight is a little hand demonstration I was taught as a student.
To represent an anticline, place a palm on top of your other hand and arch your hands upward.
When the higher land is eroded away, the rock beneath it will be exposed. Slide your top hand down, exposing your knuckles and surrounding the front with your thumb. You can see that the rock that was below is now surface rock with the other rock still surrounding it at the surface.
To represent a syncline, place one hand on top of the other palms upward. Then cup your hands as if to hold water in them.
When the higher land is eroded away, material will still remain undisturbed in the lower area. Turn your wrist so that your fingers are in the cup of the bottom hand. You can see that the rock that was below is now surrounding the rock in the center.
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