Phanerozoic eon — LLMpedia

Phanerozoic eon
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Name	Phanerozoic eon
Color	#FFD700
Time start	541.0
Caption	Worldwide marine invertebrate fossils from the Cambrian Explosion to the Holocene

Contents

Phanerozoic eon

The Phanerozoic eon marks the interval of abundant visible life preserved in the geologic record, beginning near the base of the Cambrian Period and extending to the Holocene epoch. It encompasses major intervals characterized by evolutionary radiations and mass extinctions documented across stratigraphic successions studied by institutions such as the United States Geological Survey, the British Geological Survey, and the Geological Society of London. The eon underpins frameworks used by researchers at the Smithsonian Institution, the Natural History Museum, London, and universities including Harvard University and the University of Cambridge.

Overview

The eon begins with the Cambrian boundary formalized at sections like the Fortunian GSSP near the Miaolingian and proceeds through time slices defined by bodies such as the International Commission on Stratigraphy and the International Union of Geological Sciences. Major fossil assemblages from regions such as the Burgess Shale, the Chengjiang Biota, and the Ediacara Hills inform correlations used by the Geological Society of America and by stratigraphers referencing works by Charles Doolittle Walcott, James Hall, and Ruth Henderson. Paleontological collections at the Natural History Museum, London, the American Museum of Natural History, and the Royal Ontario Museum provide type specimens central to chronostratigraphic charts produced by agencies like the International Commission on Stratigraphy.

The eon is divided into three eras recognized by the International Commission on Stratigraphy: the Paleozoic Era, the Mesozoic Era, and the Cenozoic Era. Each era comprises periods such as the Ordovician, Silurian, Devonian, Carboniferous, and Permian in the Paleozoic; the Triassic, Jurassic, and Cretaceous in the Mesozoic; and the Paleogene, Neogene, and Quaternary in the Cenozoic. Chronostratigraphic definitions are anchored at Global Boundary Stratotype Sections and Points exemplified by sites like the GSSP of Llandovery and the GSSP of Ypresian, and calibrated with radiometric standards developed by laboratories associated with Oak Ridge National Laboratory and the Max Planck Society.

The interval includes the Cambrian Explosion, the proliferation of trilobites documented by collectors linked to Royal Ontario Museum expeditions, and later radiations such as the Devonian diversification of fishes and the rise of Amniota. It records mass extinctions including the Permian–Triassic extinction event, the Cretaceous–Paleogene extinction event that impacted clades associated with Tyrannosaurus rex and Triceratops horridus, and other crises studied in contexts like the Siberian Traps and the Deccan Traps. Evolution of major groups—angiosperms, mammals, birds, cetaceans, primates—is documented in museum holdings at institutions such as the Smithsonian Institution and the Natural History Museum, London and analyzed in journals from societies including the Paleontological Society.

Phanerozoic paleoclimate history spans greenhouse intervals like the Cretaceous thermal maximum and icehouse episodes such as the Late Ordovician glaciation and the Pleistocene ice ages. Sea-level curves synthesized by researchers at the University of California, Santa Barbara and the National Oceanic and Atmospheric Administration relate to depositional sequences observed in basins like the Paris Basin, the Permian Basin, and the Western Interior Seaway. Climate forcings associated with events such as emplacement of the Siberian Traps and the Deccan Traps are linked to proxy records from cores drilled by programs like the International Ocean Discovery Program and interpreted using climate models developed at centers including the National Center for Atmospheric Research.

Plate tectonic reconfiguration across the eon involves assembly and breakup of supercontinents such as Pangea, Rodinia, and Gondwana, with uplift and basin formation evident in orogens like the Appalachian Mountains, the Himalayas, and the Ural Mountains. Paleogeographic reconstructions by groups at the Paleomap Project, the University of Texas at Austin, and the Smithsonian Institution integrate paleomagnetic data produced by laboratories including the GFZ German Research Centre for Geosciences and the Scripps Institution of Oceanography. Tectonic episodes influenced sedimentary architectures in petroleum provinces such as the North Sea, the Gulf of Mexico, and the Persian Gulf.

Chronology of the eon is established via biostratigraphy using index fossils like conodonts cataloged by the United States Geological Survey, radiometric dating methods such as uranium–lead zircon geochronology refined at Carnegie Institution for Science, and chemostratigraphy employing isotopic excursions reported by teams from Columbia University and the University of Oxford. Sequence stratigraphy frameworks popularized by authors affiliated with the Society for Sedimentary Geology and the American Association of Petroleum Geologists are applied to GSSP-defined sections and to core records archived in repositories like the British Geological Survey core library.

The eon hosts strata that supply major hydrocarbon reserves in fields developed by companies such as ExxonMobil, Royal Dutch Shell, and BP, as well as mineral deposits exploited by corporations like Rio Tinto and BHP. Paleontological and stratigraphic research funded by agencies including the National Science Foundation and the European Research Council advances understanding of biodiversity crises and recovery, informing conservation efforts tied to organizations like the IUCN. Educational outreach uses fossils from the eon in exhibits at the American Museum of Natural History, the Natural History Museum, London, and the Field Museum of Natural History to communicate Earth history to the public.

Category:Geologic eon