Global zircon analysis records a gradual rise of continental crust throughout the Neoarchean

Determining when continental masses emerged above the global ocean is crucial to understanding secular changes in crustal and Earth-surface processes. The emergence of continents above sea level provided important sinks for atmospheric CO2, a source of bioavailable P2O5, and initiated the erosional component of the rock cycle. Previous estimates for continental emergence vary widely and depend on complex geochemical proxies. Here, we formulate a testable hypothesis for the behavior of sedimentary systems in a world with flooded vs. emergent continents and employ a simple sample-based analysis of the global detrital-zircon record. Our analysis filters the total detrital zircon database from >600,000 analyses to similar to 450,000 analyses, then calculates age distribution metrics for each rock sample containing >40 individual zircon analyses. We show that watersheds with inferred sizes, relative to their host continents, similar to modern ones became common similar to 2.8 billion years ago, and that consistent crustal recycling occurred at least since the Neoarchean. In light of the extant geologic record, this analysis suggests that widespread continental emergence began at the end of the Mesoarchean and progressed throughout the Neoarchean. Our analysis therefore provides a novel chronometer to track the emergence of continental-crust throughout Earth's history. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This passage emphasizes the importance of determining when continental masses emerged above the global ocean in understanding secular changes in crustal and Earth-surface processes. By analyzing the global detrital-zircon record, the study provides a new chronometer for tracking the emergence of continental crust throughout Earth's history.