Sedimentary rock age dating
Most ancient sedimentary rocks cannot be dated radiometrically, but the laws of superposition and crosscutting relationships can be used to place absolute time limits on layers of sedimentary rocks crosscut or bounded by radiometrically dated igneous rocks.
Sediments less than about 50,000 years old that contain organic material can be dated based on the radioactive decay of the isotope Carbon 14.
Faunal Succession: Similar to the law of superposition is the law of faunal succession, which states that groups of fossil animals and plants occur throughout the geologic record in a distinct and identifiable order.
Following this law, sedimentary rocks can be “dated” by their characteristic fossil content.
If a geologist claims to be younger than his or her co-worker, that is a relative age.Relative dating techniques provide geologists abundant evidence of the incredible vastness of geologic time and ancient age of many rocks and formations.However, in order to place absolute dates on the relative time scale, other dating methods must be considered.Unlike people, you can’t really guess the age of a rock from looking at it.Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.