Tephrochronology absolute dating
Paleontologists still commonly use biostratigraphy to date fossils, often in combination with paleomagnetism and tephrochronology.
This means they provide accurate temporal marker layers which can be used to verify or corroborate other dating techniques, linking sequences widely separated by location into a unified chronology that correlates climatic sequences and events.Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed.Such an established event provides a "tephra horizon".Sometimes only one method is possible, reducing the confidence researchers have in the results. “They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.” Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts.Methods fall into one of two categories: relative or absolute.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.
Generally speaking, the more complex a poem or piece of pottery is, the more advanced it is and the later it falls in the chronology.
Paleomagnetism is often used as a rough check of results from another dating method.
Tephrochronology: Within hours or days of a volcanic eruption, tephra — fragments of rock and other material hurled into the atmosphere by the event — is deposited in a single layer with a unique geochemical fingerprint.
The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout.
Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker.
Tephrochronology requires accurate geochemical fingerprinting (usually via an electron microprobe).