Define relative dating of fossils
New dating methods are invented all the time, however, most have practical limitations.
For more information, contact Andrei Sarna-Wojcicki. Strontium Geochronology - With modern isotope separation equipment, the content of selected elemental isotopes can now be measured in concentrations to parts-per-million to parts-per-billion and beyond.Geochronology is the science of dating and determining the time sequence of events in the history of the Earth.This web page provides an overview of selected geochronology methods used by USGS scientists.Selected examples of correlation geochronology methods used by USGS scientists include: Paleomagnetic Dating - Under certain conditions, a record of the orientation of the Earth's magnetic field is preserved in rocks and sediments.Paleomagnetic dating is based on correlation of measurements derived from oriented samples to established records of variations of the Earth's magnetic field through time.Palynologists separate pollen from sediments for correlation and paleoenvironmental reconstructions.
Typically, paleontological information is used in conjunction with other methods of relative or absolute age dating.
Biostratigraphy is the science of correlation of sedimentary units base on the identifiable fossils they contain.
Paleontologists examine fossils of all kinds, but micropaleontology (the study of microscopic organisms) is perhaps the most useful method of dating because the remains of tiny organisms tend to be better preserved, more widely distributed, and may provide more precise age determinations than larger shells or bone material.
The most important tools for paleontologists are collections of fossils and paleontological reports (with fossil plates for identification) from other locations in the region or around the world.
Micropaleontologists and palynologists work with microscopes or scanning electron microscopes (SEM).
A geologic map or report typically is only a summary of investigations that frequently involve the collecting and processing of hundreds of rock samples, followed by the evaluation and interpretation of data from a variety of analytical techniques.