What three elements make up most of the earth's crust

15 points need quick 1. looking at your graph and the geologic time scale during what period did this rock form? what is the age span of the rock, in millions of years? 2. this rock sample is limestone and shale. with what you know about rock formation, what type of environment did these organisms live in? 3. if some of these fossil samples were found in a rock also containing leaf fossils, could you use radiocarbon dating to determine the age of this rock? explain.