Fossil black smoker yields oxygen isotopic composition of Neoproterozoic seawater.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29654300.
- Also identified by DOI 10.1038/s41467-018-03890-w and PMC identifier 5899122.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The evolution of the seawater oxygen isotopic composition (δ<sup>18</sup>O) through geological time remains controversial. Yet, the past δ<sup>18</sup>O<sub>seawater</sub> is key to assess past seawater temperatures, providing insights into past climate change and life evolution. Here we provide a new and unprecedentedly precise δ<sup>18</sup>O value of -1.33 ± 0.98‰ for the Neoproterozoic bottom seawater supporting a constant oxygen isotope composition through time. We demonstrate that the Aït Ahmane ultramafic unit of the ca. 760 Ma Bou Azzer ophiolite (Morocco) host a fossil black smoker-type hydrothermal system. In this system we analyzed an untapped archive for the ocean oxygen isotopic composition consisting in pure magnetite veins directly precipitated from a Neoproterozoic seawater-derived fluid. Our results suggest that, while δ<sup>18</sup>O<sub>seawater</sub> and submarine hydrothermal processes were likely similar to present day, Neoproterozoic oceans were 15-30 °C warmer on the eve of the Sturtian glaciation and the major life diversification that followed.