Rocks formed before 2.9 billion years ago have an extremely poor preservation potential (see the first figure). Thus, the late Archean marks the transition from a period of uniformly poor preservation potential to one in which the geological record is biased by the tectonic setting in which the rocks were formed. The peaks of ages illustrated in the first figure have been interpreted in terms of episodic, rather than continuous, generation of continental crust (6, 7). Such models are largely based on the records of igneous and sedimentary rocks selectively preserved in “stable” areas and are therefore biased by the formation of supercontinents. The challenge now is to explore the geological records from stages with poor preservation potential.
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