The Proterozoic record in southwestern North America documents a sequence of magmatic, deformational and metamorphic events that shaped the continent’s cratonic margin. Starting in the Mesoproterozoic ...

During the Proterozoic era, oxygen produced by photosynthesizing bacteria collects in the oceans and then in the atmosphere. Iron present in exposed rocks reacts with this oxygen, and rust colors the ...

The Proterozoic is a Precambrian eon of geologic time extending from about 2.5 billion to 541 million years ago, bounded by the Archean–Proterozoic and Proterozoic–Phanerozoic transitions. It is ...