- No rock standard has been identified formally as marking the base; at the top of the Proterozoic the Cambrian - Precambrian boundary is identified on the basis of fossils.
- This is the general name for all Archaean and Proterozoic basement gneisses of the NW Scotland mainland and Outer Hebrides.
- The bulk of the Mozambique belt of eastern Africa and Madacascar is underlain by deeply eroded and multiply deformed high-grade Proterozoic and Archaean rocks.
The Proterozoic lasted from about 2,500 million to 570 million years ago. For millions of years only bacteria, algae, and other simple organisms existed, and the early invertebrates that followed were soft-bodied and rarely left any trace in the form of fossils.
Late 19th century: from Greek proteros 'former' + zōē 'life', zōos 'living' + -ic.
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