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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 ...
The Precambrian dates from around 3850 to 542 million years ago. The Neoproterozoic is characterized by a large glaciation event, followed by the appearance of the first multicellular body plans before the Cambrian Explosion. Until the late 1950s, the Precambrian was not believed to have hosted multicellular organisms.
The Canadian Shield (French: Bouclier canadien [buklje kanadjɛ̃]), also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks.
A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. [1] These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years.
Charnia is significant because it was the first Precambrian fossil to be recognized as such. The living organism grew on the sea floor, 570 to 550 million years ago, and is believed to have fed on nutrients in the water.
1 Precambrian-Paleozoic. 2 Mesozoic. Toggle Mesozoic subsection. 2.1 Selected Mesozoic taxa of North Carolina. 3 Cenozoic. Toggle Cenozoic subsection.
The Bitter Springs Group, also known as the Bitter Springs Formation is a Precambrian fossil locality in Australia, which preserves stromatolites and microorganisms in silica. [3] Its preservational mode ceased in the late Neoproterozoic with the advent of silicifying organisms.
The Belt Supergroup is an assemblage of primarily fine-grained sedimentary rocks and mafic intrusive rocks of late Precambrian (Mesoproterozoic) age. It is more than 15 kilometres (10 mi) thick, covers an area of some 200,000 km 2 (77,220 sq. mi), and is considered to be one of the world's best-exposed and most accessible sequences of ...