Precambrian
History of Earth 4600–539 million years ago / From Wikipedia, the free encyclopedia
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The Precambrian ( /priˈkæmbri.ən, -ˈkeɪm-/ pree-KAM-bree-ən, -KAYM-;[2] or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
| Precambrian | ||||||
|---|---|---|---|---|---|---|
4567.3 ± 0.16 – 538.8 ± 0.2 Ma | ||||||
| Chronology | ||||||
| ||||||
| Proposed subdivisions | See Proposed Precambrian timeline | |||||
| Etymology | ||||||
| Synonym(s) | Cryptozoic | |||||
| Usage information | ||||||
| Celestial body | Earth | |||||
| Regional usage | Global (ICS) | |||||
| Time scale(s) used | ICS Time Scale | |||||
| Definition | ||||||
| Chronological unit | Supereon | |||||
| Stratigraphic unit | Supereonthem | |||||
| Time span formality | Informal | |||||
| Lower boundary definition | Formation of the Earth | |||||
| Lower GSSA ratified | October 5, 2022[1] | |||||
| Upper boundary definition | Appearance of the Ichnofossil Treptichnus pedum | |||||
| Upper boundary GSSP | Fortune Head section, Newfoundland, Canada 47.0762°N 55.8310°W / 47.0762; -55.8310 | |||||
| Upper GSSP ratified | 1992 | |||||
The Precambrian is an informal unit of geologic time,[3] subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about 538.8 million years ago (Ma), when hard-shelled creatures first appeared in abundance.