| Summary: | The earth system experienced a series of fundamental upheavals throughout the Archean-Paleoproterozoic transition (ca. 2500–2000 Ma). Most important were the establishment of an oxygen-rich atmosphere and the emergence of an aerobic biosphere. Fennoscandia provides a fairly complete record of the hallmark events of that transition: widespread igneous activity, its association with a possible upper-mantle oxidizing event, the global Huronian glaciation, a rise in atmospheric oxygen, the protracted and large-magnitude Lomagundi-Jatuli carbon isotope excursion, a substantial increase in the seawater sulfate reservoir, changes in the sulfur and phosphorus cycles, a radical modification in recycling of organic matter, and the Shunga Event—the accumulation of unprecedented organic-matter–rich sediments and the oldest known inferred generation of significant petroleum. Current research efforts are focused on providing an accurate temporal framework for these events and linking them into a coherent story of earth system evolution.
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