If a fossil is encased in a stratum of sedimentary rock without any strata of volcanic rock (for example, lava or ash) nearby, then it should be ________.
A) easy to determine the absolute age of the fossil, because the radioisotopes in the sediments will not have been "reset" by the heat of the igneous rocks
B) easy to determine the absolute age of the fossil, because the igneous rocks will not have physically obstructed the deposition of sediment of a single age next to the fossil
C) difficult to determine the absolute age of the fossil, because the "marker fossils" common to igneous rock will be absent
D) difficult to determine the absolute age of the fossil, because radiometric dating of sedimentary rock is less accurate than that of igneous rock

Question

Quizplus · Accepted Answer

Radiometric dating of sedimentary rock is less accurate than that of igneous rock because the radioactive isotopes used for dating are not as concentrated in sedimentary rocks, making it harder to determine the absolute age of the fossil. Additionally, without nearby igneous rocks, there may be a lack of "marker fossils" that are commonly found in igneous rocks, which can make it more difficult to correlate the age of the fossil to other rock layers.

If a Fossil Is Encased in a Stratum of Sedimentary