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).
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.
Oxygen isotope concentrations in mollusk shell and calcareous algal material normalize with seawater while the organisms are alive.
Paleontologists frequently work in conjunction with other scientists utilizing any number of other geochronology methods.
Like fossils, the chemical and physical characteristics of rocks, minerals, and organic materials can be used for correlation.
Great volcanic eruptions in the Western United States in the geologic past produced airfall deposits that have been recognized as far away as the East Coast.
The USGS maintains a tephrochronology laboratory in Menlo Park, CA.