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The Cambrian (/ ˈ k æ m b r i. ə n, ˈ k eɪ m-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. [5] The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma.
It was preceded by the less-documented (but probably more extensive) End-Botomian mass extinction around 517 million years ago, and the Dresbachian extinction event about 502 million years ago. The Cambrian–Ordovician extinction event ended the Cambrian period, and led into the subsequent Ordovician period.
It has also been suggested that the end of that second cold period [4] was responsible for the subsequent Cambrian explosion, a time of rapid diversification of multi-cellular life during the Cambrian Period. The hypothesis is still controversial, [5] [6] though is gaining credence among researchers, as evidence in its favour has mounted. [7]
The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago.
The Cambrian explosion (also known as Cambrian radiation [1] or Cambrian diversification) is an interval of time beginning approximately in the Cambrian period of the early Paleozoic, when a sudden radiation of complex life occurred and practically all major animal phyla started appearing in the fossil record.
End of the Ediacaran Period, the Proterozoic Eon and the Precambrian Supereon. The Ediacaran fauna disappears, while the Cambrian explosion initiates the emergence of most forms of complex life, including vertebrates ( fish ), arthropods , echinoderms and molluscs .
The Cambrian is a major division of the geologic timescale that begins about 538.8 ± 0.2 Ma. [40] Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. The waters of the Cambrian period appear to have been widespread and shallow. Continental drift rates may have been anomalously high.
4.2-kiloyear event dry, lasted most of the 22nd century BC, linked to the end of the Old Kingdom in Egypt, and the Akkadian Empire in Mesopotamia, various archaeological cultures in Persia and China 1800–1500: Middle Bronze Age Cold Epoch, a period of unusually cold climate in the North Atlantic region Bond Event 2