to be able to age determination of sedimentary stones, we have to index fossil the fossil which major geographical circulation and low time period. Paleontologic information supports the index fossil of every number of paleo-organisms.
Several of paleontology and stratigraphy documents allow you to figure out the chronilogical age of sedimentary stones. I would suggest the USGS website link which explain to you need for fossils and stratigraphy in your concern.
Igneous intrusions form when magma breaks through a layer of stone from beneath, or lava flows straight down from above. Continuer la lecture