Wanderlust World Wanderlust World Finding the same index fossil in rock layers in Mexico and Australia indicates those layers were deposited during the same geologic time period (relative age correlation). Index fossils are widespread, short‑lived species that serve as time markers.
Relative correlation does not provide the absolute age in years. To determine numeric ages, scientists use radiometric dating (e.g., uranium‑lead, potassium‑argon) on minerals from the same strata.
Matching index fossils = same relative age; radiometric dating = absolute age.