Evidence for land emergence in the early to middle Precambrian

Abstract

The geological record provides abundant evidence of major periods of post-orogenic uplift followed by denudation of subaerial continental terrains within the Archaean era and at the Archaean-Proterozoic boundary 2600 ± 200 Ma ago. Archaean greenstone belts, with subaerial volcanoes at least 2 km high, formed in narrow basins bordered by lands with relief of perhaps 4 km. The erosion of the borderlands gave rise to substantial terrigenous debris in the late greywackes and molasse of the greenstone belts. The high rate of radiogenic heat production in the Archaean led to more plate production, more subduction and the creation of thick-root orogenic belts, and thus eventually to substantial uplift, erosion and production of voluminous clastic sediments in the early Proterozoic. Many of these detrital beds underwent later sedimentary recycling; remnant successions are up to 13 km thick.