Publication Date:
2019
Description:
〈p〉The oxygen isotope composition (〈sup〉18〈/sup〉O) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid 〈sup〉18〈/sup〉O on the rocks’ isotopic composition. A new 〈sup〉18〈/sup〉O record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide–water oxygen isotope fractionation, suggesting that increasing seawater 〈sup〉18〈/sup〉O over time was the primary cause of the long-term rise in 〈sup〉18〈/sup〉O values of marine precipitates. The 〈sup〉18〈/sup〉O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.〈/p〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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