Relative dating techniques for fossils

21 Jan

The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa (phylogeny) are some of the most important functions of the science of paleontology.Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the arbitrary date of 10,000 years.Relative dating requires an extensive knowledge of stratigraphic succession, a fancy term for the way rock strata are built up and changed by geologic processes.

The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record.Scientists find out the age of a dinosaur fossil by dating not only the rocks in which it lies, but those below and above it.Sometimes, scientists already know the age of the fossil because fossils of the same species have been found elsewhere and it has been possible to establish accurately from those when the dinosaur lived.Paul is super awesome, so I'm going to take him at his word.But really, how do scientists figure out how old their dinosaur bones are?Consider the following scenario: Paul the Paleontologist is a very famous scientist who has studied dinosaur bones all over the world.Recently, he appeared on the evening news to talk about a new dinosaur he just discovered. Paul says he can tell from the fossils that superus awesomus lived on Earth about 175 million years ago.We'll explore both relative and numerical dating on our quest to understand the process of geological dating.Along the way, we'll learn how stratigraphic succession and radioactive decay contribute to the work of paleontologists.Like extant organisms, fossils vary in size from microscopic, even single bacterial cells one micrometer in diameter, to gigantic, such as dinosaurs and trees many meters long and weighing many tons.A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates.