What is found beneath the newer layers in horizontal sedimentary rock formations?

In horizontal sedimentary rock formations, the principle of superposition indicates that older sediment layers are found beneath newer ones. As sediment accumulates over time, the most recent deposits are laid down on top of older materials. This means that if you examine a well-preserved sequence of rock layers, you would find the oldest layers at the bottom and progressively younger layers as you move upwards. Therefore, the correct answer reflects this geological principle, providing a foundational understanding of how sedimentary rocks are structured over time.