Which statement is accurate regarding geological time?

The statement regarding fossils aiding in determining the relative ages of rocks is accurate because fossils are key indicators of the age of the rock layers in which they are found. This principle is known as biostratigraphy. Certain fossils, especially those from species that existed for a relatively short geological time but were widely distributed, act as markers for specific time periods. When scientists find these fossilized remains in sedimentary rock layers, they can correlate the ages of different rock formations across various locations. This use of fossils to establish relative timelines is a foundational concept in geology, enabling researchers to piece together the historical timeline of life on Earth and the evolution of different organisms.

In contrast, the other statements do not hold true. The oldest fossils are generally found in the lower layers of rock sequences due to the principle of superposition, where sedimentary layers are deposited over time. Ill-defined layers do not represent continuous deposition, as they may indicate periods of erosion or non-deposition. Lastly, not all rocks form under uniform geological conditions; many geological processes, such as volcanic activity, sedimentation, and metamorphism, occur under varying conditions leading to diverse rock types and formations.