Earth system transition during the Tonian–Cambrian interval of biological innovation: nutrients, climate, oxygen and the marine organic carbon capacitor
Graham A. Shields, 2017. "Earth system transition during the Tonian–Cambrian interval of biological innovation: nutrients, climate, oxygen and the marine organic carbon capacitor", Earth System Evolution and Early Life: A Celebration of the Work of Martin Brasier, A. T. Brasier, D. McIlroy, N. McLoughlin
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The Tonian–Cambrian interval (c. 0.9–0.5 Ga) witnessed major tectonic, climatic and chemical changes to the Earth system and culminated in the Ediacaran–Cambrian radiation of animals. Negative carbon isotope (δ13C) excursions of extraordinary magnitude form the backdrop to all these events and are consistent with the presence of a vast marine organic carbon reservoir that changed its size due to periodic imbalances between organic production (as an oxidant source) and terrestrial oxidant sinks. Prior to both Cryogenian glaciations, this pool of long-lived organic carbon may have become substantially depleted, leading to a weakening of the regulation of climate and oxygen. The late Ediacaran Shuram anomaly probably represents a third depletion event, which was followed by oxygenation and the Ediacaran–Cambrian radiation. The evolutionary diversification of animals shortened the ocean residence time of organic carbon and introduced new carbon cycle feedbacks that together helped to mould the modern Earth system.
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This volume in memory of Professor Martin Brasier, which has many of his unfinished works, summarizes recent progress in some of the hottest topics in palaeobiology including cellular preservation of early microbial life and early evolution of macroscopic animal life, encompassing the Ediacara biota. The papers focus on how to decipher evidence for early life, which requires exceptional preservation, employment of state-of-the-art techniques and also an understanding gleaned from Phanerozoic lagerstätte and modern analogues. The papers also apply Martin’s MOFAOTYOF principle (my oldest fossils are older than your oldest fossils), requiring an integrated approach to understanding fossils. The adoption of the null-hypothesis that all putative traces of life are abiotic until proven otherwise, and the consideration of putative fossils within their spatial context, characterized the work of Martin Brasier, as is well demonstrated by the papers in this volume.