“Precambrian”的概念、定义、翻译、参考文献-科学参考

Precambrian

Biology

Describing the time from the formation of the earth, nearly 5 billion years ago, to the start of the Cambrian period, around 541 million years ago. The term ‘Precambrian’ is no longer used for a specific geological time interval, but remains as a general adjective. Precambrian time is now divided into three eons: Hadean, Archaean, and Proterozoic, the latter extending to the start of the present (Phanerozoic) eon. Fossils are rare, although stromatolites indicate that there were flourishing populations of cyanobacteria and other bacteria. However, subsequent metamorphism of Precambrian rocks makes correlation of rocks and events extremely difficult. The largest areas of exposed Precambrian rocks are the shield areas, such as the Canadian (Laurentian) Shield and the Baltic Shield.
http://www.ucmp.berkeley.edu/precambrian/archean_hadean.php Perspectives on Precambrian time provided by the website of the University of California Museum of Paleontology

Geology and Earth Sciences

A name now used only informally to describe the Hadean, Archaean, and Proterozoic, which together comprise the longest period of geologic time that began with the consolidation of the Earth’s crust and ended approximately 4000 million years later with the beginning of the Cambrian period around 542 Ma ago. The rocks of this period of geologic time are usually altered and few fossils with hard parts or skeletons have been found within them. Precambrian rocks outcrop extensively in shield areas such as northern Canada and the Baltic Sea.

Geography

The oldest era in Earth’s history dating from about 4 600 million years bp. ‘To speak of “the Precambrian” as a single unified time period is misleading, for it makes up roughly seven-eighths of the Earth’s history’ (UCMP).
http://www.ucmp.berkeley.edu/precambrian/precambrian.html The divisions of Precambrian time.

单词	Precambrian
释义	Precambrian Biology Describing the time from the formation of the earth, nearly 5 billion years ago, to the start of the Cambrian period, around 541 million years ago. The term ‘Precambrian’ is no longer used for a specific geological time interval, but remains as a general adjective. Precambrian time is now divided into three eons: Hadean, Archaean, and Proterozoic, the latter extending to the start of the present (Phanerozoic) eon. Fossils are rare, although stromatolites indicate that there were flourishing populations of cyanobacteria and other bacteria. However, subsequent metamorphism of Precambrian rocks makes correlation of rocks and events extremely difficult. The largest areas of exposed Precambrian rocks are the shield areas, such as the Canadian (Laurentian) Shield and the Baltic Shield. http://www.ucmp.berkeley.edu/precambrian/archean_hadean.php Perspectives on Precambrian time provided by the website of the University of California Museum of Paleontology Geology and Earth Sciences A name now used only informally to describe the Hadean, Archaean, and Proterozoic, which together comprise the longest period of geologic time that began with the consolidation of the Earth’s crust and ended approximately 4000 million years later with the beginning of the Cambrian period around 542 Ma ago. The rocks of this period of geologic time are usually altered and few fossils with hard parts or skeletons have been found within them. Precambrian rocks outcrop extensively in shield areas such as northern Canada and the Baltic Sea. Geography The oldest era in Earth’s history dating from about 4 600 million years bp. ‘To speak of “the Precambrian” as a single unified time period is misleading, for it makes up roughly seven-eighths of the Earth’s history’ (UCMP). http://www.ucmp.berkeley.edu/precambrian/precambrian.html The divisions of Precambrian time.
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