Ocean deoxygenation after the Sturtian Snowball.

The abrupt ending of the Sturtian 'Snowball' glaciation was characterised by enhanced chemical weathering and carbon cycle perturbations, but there is less certainty over how oxygen levels responded to those changes. Here we reconcile conflicting views using a carbonate-based multiproxy dataset from the Taishir Formation in Mongolia. The geochemical data reveal an episode of ocean deoxygenation, followed by a shift toward less reducing, but still largely anoxic conditions in a post-glacial ocean characterised by nutrient and sulfate limitation.

Natural sampling and aliasing of marine geochemical signals.

It is well known that the sedimentary rock record is both incomplete and biased by spatially highly variable rates of sedimentation. Without absolute age constraints of sufficient resolution, the temporal correlation of spatially disjunct records is therefore problematic and uncertain, but these effects have rarely been analysed quantitatively using signal processing methods. Here we use a computational process model to illustrate and analyse how spatial and temporal geochemical records can be biased by the inherent, heterogenous processes of marine sedimentation and preservation.

The nature of the last universal common ancestor and its impact on the early Earth system.

The nature of the last universal common ancestor (LUCA), its age and its impact on the Earth system have been the subject of vigorous debate across diverse disciplines, often based on disparate data and methods. Age estimates for LUCA are usually based on the fossil record, varying with every reinterpretation. The nature of LUCA's metabolism has proven equally contentious, with some attributing all core metabolisms to LUCA, whereas others reconstruct a simpler life form dependent on geochemistry.

Dynamic redox and nutrient cycling response to climate forcing in the Mesoproterozoic ocean.

Controls on Mesoproterozoic ocean redox heterogeneity, and links to nutrient cycling and oxygenation feedbacks, remain poorly resolved. Here, we report ocean redox and phosphorus cycling across two high-resolution sections from the ~1.4 Ga Xiamaling Formation, North China Craton.

Possible links between extreme oxygen perturbations and the Cambrian radiation of animals.

The role of oxygen as a driver for early animal evolution is widely debated. During the Cambrian explosion, episodic radiations of major animal phyla occurred coincident with repeated carbon isotope fluctuations. However, the driver of these isotope fluctuations and potential links to environmental oxygenation are unclear.

Carbon and carbon isotope mass balance in the Neoproterozoic Earth system.

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.

Publisher Correction: Coupling of ocean redox and animal evolution during the Ediacaran-Cambrian transition.

The original version of this Article incorrectly gave the second address in the list of affiliations as "State Key Laboratory of Palaeobiology and Stratigraphy & Center for Excellence in Life and Paleoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 210008 Nanjing, China", instead of the correct 'State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China". This has been corrected in both the PDF and HTML versions of the Article.

Elevated CO degassing rates prevented the return of Snowball Earth during the Phanerozoic.

The Cryogenian period (~720-635 Ma) is marked by extensive Snowball Earth glaciations. These have previously been linked to CO draw-down, but the severe cold climates of the Cryogenian have never been replicated during the Phanerozoic despite similar, and sometimes more dramatic changes to carbon sinks. Here we quantify the total CO input rate, both by measuring the global length of subduction zones in plate tectonic reconstructions, and by sea-level inversion.

Tectonic controls on the long-term carbon isotope mass balance.

The long-term, steady-state marine carbon isotope record reflects changes to the proportional burial rate of organic carbon relative to total carbon on a global scale. For this reason, times of high δC are conventionally interpreted to be oxygenation events caused by excess organic burial. Here we show that the carbon isotope mass balance is also significantly affected by tectonic uplift and erosion via changes to the inorganic carbon cycle that are independent of changes to the isotopic composition of carbon input.

Palaeoclimatology: evidence for hot early oceans?

The oxygen isotopes in sedimentary cherts (siliceous sediments) have been used to argue that the Precambrian oceans were hot--with temperatures of up to 70 degrees C at 3.3 Gyr before present. Robert and Chaussidon measure silicon isotopes in cherts and arrive at a similar conclusion.