Regardless of how they formed, it would seem odd to have a rock of more than 6,000 layers in a world that is 6,000 years old. So, without using radioactive dating or astronomical dating we could try simply counting layers.
For instance, we could count the Green River formation in Wyoming. It contains more than 4,000,000 layers, or varves, identical to those being laid down today in certain freshwater lakes. The sediments are so fine that each layer would have required over a month to settle.
The basic reason for varves is that rivers run faster in the spring. A flooding river is able to carry coarse material. During the rest of the year, the river is slower, and it can only carry less-coarse material. The result is that lake bottom deposits tend to alternate, coarse/fine/coarse/fine.
Studies of present-day lakes don't always show two layers per year. There might be a cycle of 2, 3 or 4 distinct sediments, and then the same cycle repeats. But in the Green River varves, the cycle has only two layers - a fine light sediment, and an even finer dark sediment.
And of course the occasional storm might add an extra layer. However, this hardly turns millions of layers into a 6,000 year project.