Biostratigraphy: One of the first and most basic scientific dating methods is also one of the easiest to understand.Layers of rock build one atop another — find a fossil or artifact in one layer, and you can reasonably assume it’s older than anything above it.While K-Ar dating requires destroying large samples to measure potassium and argon levels separately, Ar-Ar dating can analyze both at once with a single, smaller sample.Uranium series dating: U-series dating includes a number of methods, each based on different uranium isotopes’ decay rates.Researchers can measure the amount of these trapped electrons to establish an age.But to use any trapped charge method, experts first need to calculate the rate at which the electrons were trapped.For example, New Zealand’s massive Taupo volcano erupted in A. Relative chronology: Researchers have often constructed timelines of a culture or civilization based on the stylistic evolution of its decorative or dramatic arts — that’s why the method is also sometimes called stylistic seriation.
Both methods date rock instead of organic material. But unlike radiocarbon dating, the older the sample, the more accurate the dating — researchers typically use these methods on finds at least 500,000 years old.
Researchers can first apply an absolute dating method to the layer.
They then use that absolute date to establish a relative age for fossils and artifacts in relation to that layer. Anything below the Taupo tephra is earlier than 232; anything above it is later.
Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating.
These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating.