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10 Be/ 9 Be Ratios Reveal Marine Authigenic Clay Formation
Author(s) -
Bernhardt A.,
Oelze M.,
Bouchez J.,
Blanckenburg F.,
Mohtadi M.,
Christl M.,
Wittmann H.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl086061
Subject(s) - authigenic , weathering , geology , sediment , seawater , mineralogy , coprecipitation , clay minerals , geochemistry , transect , environmental chemistry , oceanography , geomorphology , chemistry , inorganic chemistry
As reverse weathering has been shown to impact long‐term changes in atmospheric CO 2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio ( 10 Be/ 9 Be) recorded in marine clay‐sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders‐of‐magnitude difference in 10 Be/ 9 Be ratios between continental Be and Be dissolved in seawater. On marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay‐sized fraction to compare the riverine and marine 10 Be/ 9 Be ratio of this fraction. 10 Be/ 9 Be ratios increase fourfold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10 Be/ 9 Be from dissolved biogenic opal, which also serves as a Si‐source for the precipitation of marine authigenic clays. 10 Be/ 9 Be ratios thus sensitively track reverse‐weathering reactions forming marine authigenic clays.