For instance, even though the Grand Canyon sits on a plateau 7,500 feet above sea level, there are marine fossils in its rock beds. In addition to being readers of rocks, geologists are Earth detectives. They collect clues from their observations of the geologic record to figure out what happened in the Earth's past. Sedimentary Rocks Let's start our own investigation by looking at sedimentary rocks . All this sediment gets carried along and then left by things like water, wind, and glaciers.
Most sedimentary rocks come from sediments deposited on the margins of the ocean.
As more and more sediment is deposited on top, the older sediment gets buried. This burial results in compaction and cementation. This overall process is called lithification , which is basically the process of turning a sediment into a sedimentary rock. Often, plant and animal remains that were present in the sediment are preserved in the sedimentary rock. Scientists get pretty excited when they come across the preserved remains of some wacky prehistoric thing, because the remains are big clues to the Earth's past.