The case for a Neoproterozoic Oxygenation Event: Geochemical evidence and biological consequences (original) (raw)
Related papers
The Neoproterozoic Oxygenation Event: Environmental perturbations and biogeochemical cycling
Earth-Science Reviews, 2011
The oxygen content of the Earth's surface environment is thought to have increased in two broad steps: the Great Oxygenation Event (GOE) around the Archean-Proterozoic boundary and the Neoproterozoic Oxygenation Event (NOE), during which oxygen possibly accumulated to the levels required to support animal life and ventilate the deep oceans. Although the concept of the GOE is widely accepted, the NOE is less well constrained and its timing and extent remain the subjects of debate. We review available evidence for the NOE against the background of major climatic perturbations, tectonic upheaval related to the break-up of the supercontinent Rodinia and reassembly into Gondwana, and, most importantly, major biological innovations exemplified by the Ediacarian Biota and the Cambrian 'Explosion'. Geochemical lines of evidence for the NOE include perturbations to the biogeochemical cycling of carbon. Generally high δ 13 C values are possibly indicative of increased organic carbon burial and the release of oxidative power to the Earth's surface environment after c. 800 Ma. A demonstrably global and primary record of extremely negative δ 13 C values after about 580 Ma strongly suggests the oxidation of a large dissolved organic carbon pool (DOC), the culmination of which around c. 550 Ma coincided with an abrupt diversification of Ediacaran macrobiota. Increasing 87 Sr/ 86 Sr ratios toward the Neoproterozoic-Cambrian transition indicates enhanced continental weathering which may have fuelled higher organic production and burial during the later Neoproterozoic. Evidence for enhanced oxidative recycling is given by the increase in sulfur isotope fractionation between sulfide and sulfate, exceeding the range usually attained by sulfate reduction alone, reflecting an increasing importance of the oxidative part in the sulfur cycle. S/C ratios attained a maximum during the Precambrian-Cambrian transition, further indicating higher sulfate concentrations in the ocean and a transition from dominantly pyrite burial to sulfate burial after the Neoproterozoic. Strong evidence for the oxygenation of the deep marine environment has emerged through elemental approaches over the past few years which were able to show significant increases in redox-sensitive trace-metal (notably Mo) enrichment in marine sediments not only during the GOE but even more pronounced during the inferred NOE. In addition to past studies involving Mo enrichment, which has been extended and further substantiated in the current review, we present new compilations of V and U concentrations in black shales throughout Earth history that confirm such a rise and further support the NOE. With regard to ocean ventilation, we also review other sedimentary redox indicators, such as iron speciation, molybdenum isotopes and the more ambiguous REE patterns. Although the timing and extent of the NOE remain the subjects of debate and speculation, we consider the record of redox-sensitive trace-metals and C and S contents in black shales to indicate delayed ocean ventilation later in the Cambrian on a global scale with regard to rising oxygen levels in the atmosphere which likely rose during the Late Neoproterozoic.
Interface Focus, 2020
One contribution of 15 to a theme issue 'The origin and rise of complex life: integrating models, geochemical and palaeontological data'. A hypothesized rise in oxygen levels in the Neoproterozoic, dubbed the Neoproterozoic Oxygenation Event, has been repeatedly linked to the origin and rise of animal life. However, a new body of work has emerged over the past decade that questions this narrative. We explore available proxy records of atmospheric and marine oxygenation and, considering the unique systema-tics of each geochemical system, attempt to reconcile the data. We also present new results from a comprehensive COPSE biogeochemical model that combines several recent additions, to create a continuous model record from 850 to 250 Ma. We conclude that oxygen levels were intermediate across the Ediacaran and early Palaeozoic, and highly dynamic. Stable, modern-like conditions were not reached until the Late Palaeozoic. We therefore propose that the terms Neoproterozoic Oxygenation Window and Palaeozoic Oxygen-ation Event are more appropriate descriptors of the rise of oxygen in Earth's atmosphere and oceans.
Earth history. Low mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals
Science (New York, N.Y.), 2014
The oxygenation of Earth's surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth's surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans.
Nature Geoscience, 2024
A geologically rapid Neoproterozoic oxygenation event is commonly linked to the appearance of marine animal groups in the fossil record. However, there is still debate about what evidence from the sedimentary geochemical record—if any—provides strong support for a persistent shift in surface oxygen immediately preceding the rise of animals. We present statistical learning analyses of a large dataset of geochemical data and associated geological context from the Neoproterozoic and Palaeozoic sedimentary record and then use Earth system modelling to link trends in redox-sensitive trace metal and organic carbon concentrations to the oxygenation of Earth’s oceans and atmosphere. We do not find evidence for the wholesale oxygenation of Earth’s oceans in the late Neoproterozoic era. We do, however, reconstruct a moderate long-term increase in atmospheric oxygen and marine productivity. These changes to the Earth system would have increased dissolved oxygen and food supply in shallow-water habitats during the broad interval of geologic time in which the major animal groups first radiated. This approach provides some of the most direct evidence for potential physiological drivers of the Cambrian radiation, while highlighting the importance of later Palaeozoic oxygenation in the evolution of the modern Earth system.
Emerging views on the evolution of atmospheric oxygen during the Precambrian
Journal of Mineralogical and Petrological Sciences, 2005
The oxygenation of the atmosphere produced some irreversible changes in the Earth's history, including evolution of higher biological forms. Several aspects of this important process, such as its timing and causes, have remained subjects of debate. The present review is an attempt to provide an update on issues related to the evolution of atmospheric oxygen during the Precambrian. It is generally believed that the amount of atmospheric oxygen increased during the Paleoproterozoic despite the fact that photosynthesis originated much earlier in the Earth's history. The pattern of Fe retention in paleosols and the record of mass independent fractionation in sulfur isotopes confirm that the transition to more oxidizing conditions took place during the Paleoproterozoic.
Anoxia in the terrestrial environment during the late Mesoproterozoic
A signifi cant body of evidence suggests that the marine environment remained largely anoxic throughout most of the Precambrian. In contrast, the oxygenation history of terrestrial aquatic environments has received little attention, despite the signifi cance of such settings for early eukaryote evolution. To address this, we provide here a geochemical and isotopic assessment of sediments from the late Mesoproterozoic Nonesuch Formation of central North America. We utilize rhenium-osmium (Re-Os) geochronology to yield a depositional age of 1078 ± 24 Ma, while Os isotope compositions support existing evidence for a lacustrine setting. Fe-S-C systematics suggest that the Nonesuch Formation was deposited from an anoxic Fe-rich (ferruginous) water column. Thus, similar to the marine realm, anoxia persisted in terrestrial aquatic environments in the Middle to Late Proterozoic, but sulfi dic water column conditions were not ubiquitous. Our data suggest that oxygenation of the terrestrial realm was not pervasive at this time and may not have preceded oxygenation of the marine environment, signifying a major requirement for further investigation of links between the oxygenation state of terrestrial aquatic environments and eukaryote evolution.
Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age
Proceedings of the National Academy of Sciences, 2009
Molecular oxygen (O2) began to accumulate in the atmosphere and surface ocean ca. 2,400 million years ago (Ma), but the persistent oxygenation of water masses throughout the oceans developed much later, perhaps beginning as recently as 580 -550 Ma. For much of the intervening interval, moderately oxic surface waters lay above an oxygen minimum zone (OMZ) that tended toward euxinia (anoxic and sulfidic). Here we illustrate how contributions to primary production by anoxygenic photoautotrophs (including physiologically versatile cyanobacteria) influenced biogeochemical cycling during Earth's middle age, helping to perpetuate our planet's intermediate redox state by tempering O 2 production. Specifically, the ability to generate organic matter (OM) using sulfide as an electron donor enabled a positive biogeochemical feedback that sustained euxinia in the OMZ. On a geologic time scale, pyrite precipitation and burial governed a second feedback that moderated sulfide availability and water column oxygenation. Thus, we argue that the proportional contribution of anoxygenic photosynthesis to overall primary production would have influenced oceanic redox and the Proterozoic O 2 budget. Later Neoproterozoic collapse of widespread euxinia and a concomitant return to ferruginous (anoxic and Fe 2؉ rich) subsurface waters set in motion Earth's transition from its prokaryote-dominated middle age, removing a physiological barrier to eukaryotic diversification (sulfide) and establishing, for the first time in Earth's history, complete dominance of oxygenic photosynthesis in the oceans. This paved the way for the further oxygenation of the oceans and atmosphere and, ultimately, the evolution of complex multicellular organisms.
Japan Geoscience Union, 2015
The terminal Proterozoic to earliest Phanerozoic (650-500 Ma) is a critical period of life evolution on Earth, marked by the emergence of the (i) Lantian biota, (ii) diversification of the Ediaraca biota, and (iii) the Early Cambrian Metazoan Explosion. These three bioevents apparently set an evolutionary agenda for animals to eventually proliferate on Earth during the Phanerozoic. Although a causal link between environmental amelioration and metazoan emergence or proliferation in the mid-Ediacaran (580 Ma) has been discussed, the precise relationship between environmental changes, in particular redox condition changes and these three major bioevents have long remained disputed. We investigated sedimentary organic molecules from 660 to 510 Ma as a proxy for redox conditions in three water depth settings, surface water, shallow intermediate water, and deep intermediate water. Samples were taken from South China, Oman, and Australia. Those data show that three major oxidations in the intermediate water occurred just after the Marinoan Snowball Earth (635 Ma), the Gaskiers Glaciation to the Shuram event (580-555 Ma), and in the earliest Cambrian (515-525 Ma). These oceanic oxidation events coincided with the emergence of the Lantian Biota, the proliferation of the early Ediacaran Biota, and Cambrian explosion, respectively. Moreover, this analysis also shows that anoxia occurred in surface water during the Marinoan Glaciation and Ediacaran-Cambrian boundary, across which the Ediacaran Biota were wiped out. Thus, oceanic redox condition changes played a crucial role driving the origination, evolution and extinction of early animals.