Why is it that the angular unconformities all seem to be relatively in conjuction with the surface?
Just maybe because stuff near the surface is visible, and buried stuff isn't?
Seismic studies show lots of unconformities in the subsurface, sometimes stacked on top of others. The oil fields around beautiful Velma, Oklahoma are a fine example. The SACROC unit 6500 feet beneath my desk is another.
Isn't it possible that these could have happened in less than 4000 years?
No. See comments on metamorphism above.
And the SACROC makes oil out of a huge coral/sponge reef - they don't grow real fast. The surface of the reef is eroded and cut up by streams and rivers - those don't erode corals all that quick. The whoe mess is buried by over a mile of dolomites, shales, gypsum beds, red sandstones of desert origin, layers of salt, limestones, anf then dirt. That didn't happen fast, and it didn't happen in a Floode.