There are a host of other clues or enviromental indicators that provide evidence of the environment of deposition of sedimentary rocks.
Dinosaur footprints in this mudstone near Tuba City Arizona tell us that this rock must have formed in an environment that was at least periodically above sea level. A full development of the science of environmental indicators is beyond the scope of this tutorial. For us, it's sufficient to know simply that sedimentary rocks tell about these ancient enviroments. Our goal is to assemble the sequence of events that produced the rocks we see.