Re-inventing the planet: the Neoproterozoic revolution in oxygenation, biogeochemistry and biological complexity

Lead Research Organisation: University College London
Department Name: Earth Sciences

Abstract

The Earth is a truly remarkable planet. In addition to the physical processes driving plate tectonics, climate and ocean-atmospheric exchange, it supports an extraordinary diversity of living organisms, from microbes to mammals and everything in between. Such wasn't always the case, however, and it is clear that both the planet and its biosphere have evolved - indeed, co-evolved - over deep time. In the past two billion years, by far the most fundamental shift in this co-evolutionary process occurred during the Neoproterozoic (1000 to 542 million years ago), a planetary revolution that culminated in the modern Earth system. The Neoproterozoic begins with a biosphere populated almost exclusively by microbes, and ends in the midst of its greatest ever evolutionary radiation - including the diverse macroscopic and biomineralizing organisms that define the modern biosphere. At the same time, it witnessed the greatest climatic and biogeochemical perturbations that the planet has ever experienced, alongside major palaeogeographic reconfigurations and a deep ocean that is becoming oxygenated for the first time. There is no question that these phenomena are broadly interlinked, but the tangle of causes, consequences and co-evolutionary feedbacks has yet to be convincingly teased apart. In order to reconstruct the Neoproterozoic revolution, we propose a multidisciplinary programme of research that will capture its evolving geochemical and biological signatures in unprecedented detail. Most significantly, these collated data will be assessed and modeled in the context of a co-evolving Earth system, whereby developments in one compartment potentially facilitate and escalate those in another, sometimes to the extent of deriving entirely novel phenomena and co-evolutionary opportunities. Our approach will be guided by three general hypotheses, testable against accruing data and theory: H1) that the enhanced weathering associated with land-dwelling eukaryotes was initiated in the early Neoproterozoic leading to major environmental change, including extreme glaciations and stepwise increase(s) in atmospheric oxygen concentration; H2) that major environmental changes in the mid Neoproterozoic triggered the emergence of animals; and H3) that the late Neoproterozoic-Cambrian radiations of animals and biomineralization were themselves responsible for much of the accompanying biogeochemical perturbation. Primary data for this project will be assembled from field studies of key geological sections in the UK and North China, along with contributed sample sets from Namibia, Spitsbergen and various archived collections. Together, these offer close to comprehensive coverage of the Neoproterozoic - not least, spectacular new surfaces of Ediacaran macrofossils from Charnwood Forest. Collected samples will be analysed to assess associated weathering and climate (Sr, C, O and S isotopes), oceanic redox conditions (Fe speciation and trace metals), nutrient dynamics (P speciation and trace metals) and biological constituents (microfossils, macrofossils and biomarker molecules). These data will be integrated and interrogated through the development of heuristic, spatial and evolutionary models. Beyond its integrative approach, the strength of this proposal lies in the diversity of the contributing researchers. Alongside our own expertise in biogeochemistry, palaeobiology and Earth system modelling, we are very pleased to have attracted world-class project partners in Neoproterozoic stratigraphy, geochronology and biomarker analysis. Further insight will come from our contingent of two PDRAs and three PhD students working across the range of topics and linked via a schedule of regular team meetings. Taken together, we anticipate a fundamentally improved understanding of the Neoproterozoic Earth system and the co-evolutionary interplay between the biosphere and planet.

Publications

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He T (2017) Measuring the 'Great Unconformity' on the North China Craton using new detrital zircon age data in Geological Society, London, Special Publications

 
Description We have used field-based geochemical and geological data to test novel theories of how the evolution of complex life and animals both influenced and was influenced by their environment. In particular, we have found evidence that normal animal behaviours (e.g. burrowing) help to control atmospheric oxygen levels. Our geochemistry work has shown that the eariest animal-based reefs encountered major fluctuations in oxygen levels, that glaciations (Snowball Earth) were preceded by important changes in chemical weathering on a global scale, and have contributed to a better understanding of how the modern Earth system came into being. Most recently, we have discovered how weathering processes can affect the long-term carbon cycle and our understanding of how the atmosphere and oceans became oxygenated.
Exploitation Route We hope that the feedbacks identified in our study will inform future climate and earth system models.
Sectors Environment

URL http://www.lifeandplanet.net/project-i-reinventing-the-planet.html
 
Description Our findings and group collaborations have acted as a focus for six early career workshops in the UK and China, the last of which attracted over 50 participants from all over China. This has set the stage for a new Sino-UK co-funded research programme in the field of 'Biosphere Evolution, Transitions and Resilience' to begin during the course of 2016.
First Year Of Impact 2016
Sector Education
Impact Types Societal

 
Description Negative feedbacks: Snowball Earth, the Cambrian explosion and the Industrial Revolution 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Invited lecture at Nanjing University, China followed by long afternoon discussion with research group there

Request for further collaboration
Year(s) Of Engagement Activity 2013
 
Description Snowball Earth and the beginnings of animal evolution 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Schools
Results and Impact Popular science lecture for over 100 school pupils and science teachers from Greater London which sparked half-an-hour of questions afterward

Several requests for further information
Year(s) Of Engagement Activity 2013
URL https://lecturecast.ucl.ac.uk:8443/ess/echo/presentation/a3e3c381-b0f2-429a-9df0-424abefd5471
 
Description Why no Phanerozoic Snowball Earth? Changes in biogeochemical cycling across the Precambrian-Cambrian transition 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Invited lecture at Cambridge University

n/a
Year(s) Of Engagement Activity 2013