Precambrian perspectives.

The Precambrian record is interpreted in terms of an evolutionary progression that moves in the direction of increasing continental stability. An early, highly mobile microplate tectonics phase progressed through a more stable, largely intracratonic, ensialic, mobile belt phase to the modern macroplate tectonics phase that involves large, rigid lithospheric plates. Various phases are characterized by distinctive crustal associations. Three controls-bulk earth heat production, crustal fractionation and cratonization, and atmospheric oxygen accumulation-are viewed as the cumulative cause of the trends and events that characterize the crust at different stages of development, from its inception approximately 4.6 billion years ago to the present.