Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon.
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Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon.
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The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells.
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Cambrian marked a profound change in life on Earth: prior to the Cambrian, the majority of living organisms on the whole were small, unicellular and simple .
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The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of all modern animal phyla.
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Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period.
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The use of Treptichnus pedum, a reference ichnofossil to mark the lower boundary of the Cambrian, is problematic because very similar trace fossils belonging to the Treptichnids group are found well below T pedum in Namibia, Spain and Newfoundland, and possibly in the western USA.
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The Cambrian is divided into several regional faunal stages of which the Russian-Kazakhian system is most used in international parlance:.
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Lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites.
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In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into an epicontinental sea.
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The later half of Cambrian was surprisingly barren and showed evidence of several rapid extinction events; the stromatolites which had been replaced by reef building sponges known as Archaeocyatha, returned once more as the archaeocyathids became extinct.
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Some Cambrian organisms ventured onto land, producing the trace fossils Protichnites and Climactichnites.
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In contrast to later periods, the Cambrian fauna was somewhat restricted; free-floating organisms were rare, with the majority living on or close to the sea floor; and mineralizing animals were rarer than in future periods, in part due to the unfavourable ocean chemistry.
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