The Neoproterozoic Earth system was significantly different from the modern world, as evidenced by extraordinary carbon isotope fluctuations that defy conventional explanation. Because Earth's carbon and oxygen budgets must be balanced on very long time scales (>105 years), such prolonged excursions can best be explained by invoking a vast pool of dissolved organic matter (DOM) in the world's oceans and its remineralisation by surplus oxidant after pyrite burial. The episodic waxing and waning of a DOM reservoir helps to explain the occurrence and timing of extreme climate events during the Neoproterozoic Era. Ecological dominance by eukaryotes, such as animals and algae, arose from a series of opportunistic radiations of aerobic life forms during periods of net DOM remineralisation and oxygenation.
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Cover Image
Cover Image
Gently inclined strata of the upper Bylot Supergroup in Edwin Inlet, Baffin Island (Canada). Bangiomorpha pubescens, a fossil red alga and the oldest taxonomically resolved eukaryote, occurs in the Bylot Supergroup and equivalent rocks in northeastern Canada. Recent radiometric dating has tightly constrained the first appearance of this fossil to ca. 1045 million years ago. Image kindly provided by Galen Halverson (McGill University), who with his co-authors in this issue, reviews the methods by which the Proterozoic time scale is dated and provide an up-to-date compilation of age constraints on key fossil first and last appearances, geological events, and horizons during the Tonian and Cryogenian periods. Their article also develops a new age model for a ca. 819–740 Ma composite section in Svalbard. For details, see pages 137–147.
Carbon and carbon isotope mass balance in the Neoproterozoic Earth system
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