Complete question:
Which characteristic is most useful in correlating Devonian-age sedimentary bedrock in New York State with Devonian-age sedimentary bedrock in other parts of the world?
a. Color
b. Index fossils
c. Rock types
d. Particle size
Answer:
b. Index fossils
Step-by-step explanation:
Fossils are animal and vegetable rests found in different strata of sedimentary rocks. Sedimentary layers deposit chronologically, so they are used to reflect history. They keep in each layer some of the forms of life that inhabited that area in the past. These fossils turn to be very useful while dating ages. The term Index fossils refer to those fossils that only existed in a given era or geological period during evolution.
Index fossils must:
- Be easily recognizable and distinguishable from all the other fossils
- Have lived in a relatively short geological period
- Present a wide geographic distribution
- Have lived in different sedimentary basins
- Appear in different types of rocks
- Be abundant
In the exposed example, we are looking for a correlation between the Devonian-age sedimentary rock layers from New York with the Devonian layers of other parts of the world. This comparison is the same period (Devonian) and in places that might be far away from each other, meaning there was a wide geographical distribution of the species.
A quick evolution and extinction contribute to narrow the geological period of their existence, increasing the chronological precision. Widely distributed fossils allow geologists to establish relationships between rocks that are far away from each other.