Start Relative age dating of sedimentary rocks

Relative age dating of sedimentary rocks

You might have noticed that many of the oldest age dates come from a mineral called zircon.

No bones about it, fossils are important age markers.

But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.

There are two basic approaches: relative age dating, and absolute age dating.

Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.

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.

In a way this field, called geochronology, is some of the purest detective work earth scientists do.

This is what archaeologists use to determine the age of human-made artifacts. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old.

Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.

With absolute age dating, you get a real age in actual years.

It’s based either on fossils which are recognized to represent a particular interval of time, or on radioactive decay of specific isotopes. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times.

Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.