Proterozoic

The Proterozoic rock record shows many features that suggest that large continents were present in this interval, including the first appearance in the geological record of very thick and abundant mature quartz sandstones, although some smaller examples are known from the Archean. These sedimentary rocks include well-sorted quartzites and quartz-rich graywackes, and indicate long periods of abrasion on stable continental shelves, and in some cases are depositionally related to abundant limestones that contain shallow-water fossils called stromatolites. These types of sedimentary assemblages indicate long-term sedimentation on a big stable continent, and are considered to mark the time when many small plates characteristic of the Archean graded into larger plates of the Proterozoic and younger times.

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