The evolution of Earth's surficial Mg cycle over the past 2 billion years.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38427740.
- Also identified by DOI 10.1126/sciadv.adj5474 and PMC identifier 10906924.
- Licence recorded as CC BY-NC.
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Abstract
The surficial cycling of Mg is coupled with the global carbon cycle, a predominant control of Earth's climate. However, how Earth's surficial Mg cycle evolved with time has been elusive. Magnesium isotope signatures of seawater (δ<sup>26</sup>Mg<sub>sw</sub>) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth's history. Here, we present a reconstruction of δ<sup>26</sup>Mg<sub>sw</sub> evolution over the past 2 billion years using marine halite fluid inclusions and sedimentary dolostones. The data show that δ<sup>26</sup>Mg<sub>sw</sub> decreased, with fluctuations, by about 1.4‰ from the Paleoproterozoic to the present time. Mass balance calculations based on this δ<sup>26</sup>Mg<sub>sw</sub> record reveal a long-term decline in net dolostone burial (NDB) over the past 2 billion years, due to the decrease in dolomitization in the oceans and the increase in dolostone weathering on the continents. This underlines a previously underappreciated connection between the weathering-burial cycle of dolostone and the Earth's climate on geologic timescales.