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Precambrian (Geology Dictionary)

Precambrian : A non-standard geologic time period immediately preceding the Phanerozoic Eon, divided into several eons of the geologic time scale. It spans from the formation of Earth about 4540 Ma (million years ago) to the beginning of the Cambrian Period, about 541.0 ± 1.0 Ma, when macroscopic hard-shelled animals first appeared in abundance.

_ ស្វែងរកឬបកប្រែពាក្យផ្សេងទៀតនៅប្រអប់នេះ៖
_ខាងក្រោមនេះជាសៀវភៅនិងឯកសារសម្រាប់ការងារនិងរៀនគ្រប់ប្រភេទ៖
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