Index fossil relative dating
Evolution explains the observed faunal and floral succession preserved in rocks.
Faunal succession was documented by Smith in England during the first decade of the 19th century, and concurrently in France by Cuvier (with the assistance of the mineralogist Alexandre Brongniart).
For each dating or chronological method there is a link in the box at right to take you to that section of this page.
There, you will find a brief description of the method, plus links to take you to other webpages with more extensive information.
Ammonoids characterized by a more highly folded suture, called ceratite, replaced the goniatites and were most abundant in the Triassic Period (252 million to 201 million years ago).
For instance, paleontologists investigating the evolution of birds predicted that feathers would first be seen in primitive forms on flightless predecessor organisms such as feathered dinosaurs.
They hypothesize that the sudden decline of plankton during the K–T extinction at the end of the Cretaceous brought about the demise of the remaining ammonoid groups.
The principle of faunal succession, also known as the law of faunal succession, is based on the observation that sedimentary rock strata contain fossilized flora and fauna, and that these fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances.
In Cenozoic strata, fossilized tests of foraminifera are often used to determine faunal succession on a refined scale, each biostratigraphic unit (biozone) being a geological stratum that is defined on the basis of its characteristic fossil taxa. Simply, the earlier fossil life forms are simpler than more recent forms, and more recent forms are most similar to existing forms (principle of faunal succession).
An outline microfaunal zonal scheme based on both foraminifera and ostracoda was compiled by M.
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