Stratigraphy of a bank cut in a stream at Covered Bridge Park, Boston, Ohio.
The lowest levels are from the last glaciation event, which ended around 10-12,000 years ago, and are composed of large (golfball to softball) sized rocks. The layers lying over were deposited through sedimentation when the creek would flood, laying a fresh layer of sediment over the ground.
I would kill to carbon date the log in the last picture. I wonder how long it had been sitting there and how old it is.