Sedimentary rock is a rock that is formed from the igneous rocks by the process of weathering and erosion and this rock contains layers of sediments and them on being exposed forms various layers depending on the geologic history of the earth.
It is through the process of radiometric dating that the sedimentary rock is studied and the fossil records are found.
Thus That is classified into as siliciclastic, carbonate and evaporite, Iron-rich and phosphatic rocks. The fossils in these rocks are formed due to the transportation deposition of the ancient prehistoric animals and plants remains in them.
Hence the depth of the rock layers of the rocks tells us of the rock type its age and the older the rock is the older will be its formation and the older will be its chemical constitution thus the calm fossil will be older as the sedimentary rock has preserved this as they are made up of shells and are hard.
