Railsback's Some Fundamentals of Mineralogy and Geochemistry The standard geologic time scale MYBP (millions of years MYBP (millions of years MYBP before present) Era Era PeriodEpoch Eon Era Period before present) 0 Beginning 0 0 Holocene of present CENOZOIC QUATERNARY 0.01 interglacial Major 2.6 phase NARY Pleistocene 65 NEOGENE QUATER- ERO- extinction 23 2.6 First major MESOZOIC ZOIC 251 events CENO- PALEOGENE Northern 65 Pliocene Hemisphere PALEOZOIC 5 glaciation PHAN ZOIC 0.54 billion years ago 542 CRETACEOUS * Miocene (age of Earth's oldest easily NEOGENE 23 recognized fossils) 145 Oligocene CENOZOIC TERTIARY First cooling Neoproterozoic 34 JURASSIC from Eocene Cretaceous- Mesoproterozoic MESOZOIC 200 56 to-Eocene warm period TRIASSIC PALEOGENE Paleocene "Great 65 Paleoproterozoic Oxidation 251 The geologic time scale attempts to Event" PERMIAN give names to meaningful periods of PROTEROZOIC 2.5 billion years ago 299 time in Earth history, just as scholars of (an arbitrary numerological 2500 PENNSYLVANIAN American history speak of a "colonial boundary) 318 period", an "antebellum period", and so MISSISSIPPIAN on. Note the decreasing size of time Late Archean 359 periods closer to the present (i.e., to the top of diagram). We live in the DEVONIAN most recent days of the Holocene Middle Archean Epoch of the Quaternary Period of the PRECAMBRIAN 416 SILURIAN Cenozoic Era of the Phanerozoic Eon. ARCHEAN Early Archean 444 *In the first decade of the 21st Century, the International Commission on 3.8 billion years ago PALEOZOIC ORDOVICIAN Stratigraphy divided the Cenozoic period (more or less age of Earth's 3800 previously known as "the Tertiary " into oldest surviving rocks) 488 "Paleogene" and "Neogene". Much Hadean CAMBRIAN literature still uses the word "Tertiary" (Hadean time is included within the and the letter "T" as its abbreviation. Archean by many geologists.) Many Earth scientists also continue to 542 refer to the boundary at the end of the Millions of HADEAN 4.6 billion years ago Ediacaran Cretaceous as the "K-T" boundary, even years before though it would be the "K-P" boundary in (age of Earth) 4600 Millions of years present the new usage. before present After Stanley's Earth System History (3rd edn 2009) LBR Stanley11aLS 8/1999; rev 10/2010.