Can we determine the ages of glacial events from the fossil record?
Most geologically recent fossils in Maine are found in the marine clays deposited shortly after recession of the Laurentide Ice Sheet. If they are well preserved, samples of shells, wood, etc. can be sent to a laboratory for radiocarbon dating (based on their content of the carbon-14 isotope). The ages obtained in this manner are approximate and must be adjusted to determine their equivalents in actual calendar years. In most cases, ages of fossils from marine clays only tell us that the glacier was gone by a certain time. However, fossils are occasionally found in sediments formed right at the glacier margin, and then we can get a more definite timing of glacial retreat from different parts of Maine.
