The manner in which the sediments are being deposited unless the disturbance by tectonic processes makes it non sequential is theorized with the principle of superposition.
Explanation:
The principle of superposition lets us know that the oldest sediment layer is at the bottom with the newer at the top. For example, xenolith in igneous rock must be older than the rock it contains.
The formation of sedimentary rocks is done via sedimentation occurring in the sequential basis. Due to tectonic process or disruption or even say faults, the layers are sediment in non sequential manner. The entire manner of sequential layering gets turn upside down.
