Waltham, MA: Fossil assemblage B includes the index fossils the orange ammonite and the blue ammonite, meaning that assemblage B must have been deposited during the interval of time indicated by the red box. Scientists find out the age of a dinosaur fossil by dating not only the rocks in which it lies, but those below and above it. The principle states that any geologic features that cut across strata must have formed after the rocks they cut through Figures 2 and 3. This matching process is called correlation, which has been an important process in constructing geological timescales. Interval of time when the earth's magnetic field is oriented so that the magnetic north pole is approximately in the same position as the geographic north pole.
Ecology and population biology Marine mammals:
18.5D: Carbon Dating and Estimating Fossil Age
Read on to find out! Behavior and life history Marine mammals: Cities U.