Molybdenum isotope constraints on the temporal development of sulfidic conditions during Mediterranean sapropel intervals

T. Sweere; R. Hennekam; D. Vance; G. J. Reichart

doi:10.7185/geochemlet.2108

Molybdenum isotope constraints on the temporal development of sulfidic conditions during Mediterranean sapropel intervals

T. Sweere^*, R. Hennekam, D. Vance, G. J. Reichart

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Mediterranean sapropels represent some of the largest scale deoxygenation events in recent Earth history. Here, we use high resolutionMo isotope data for seven such events (sapropels S3 to S9) to semi-quantitatively constrain past H2S concentrations using a new interpretive framework. Bottom water H2S was present for all studied sapropels, but the extent of redox changes varied considerably between them, the ultimate driver likely being variations in monsoon strength. Nearquantitative removal of Mo (δ98Mo > 2‰) during deposition of sapropels S5 and S7 suggests predominantly highly sulfidic conditions with long deep water residence times, comparable to the modern Black Sea, whereas considerably lower δ98Mo values for sapropels S3, S4, S8, and S9 (-0.4 to +0.9‰) imply mildly euxinic conditions only (0 <H2S < 11 μmol/L). The high resolution data reveal consistent temporal patterns that track the development of basin restriction and euxinia over several kyr. These observations illustrate how Mo isotopes can provide quantitative constraints on basin wide redox changes on relatively short time scales.

Original language	English
Pages (from-to)	16-20
Number of pages	5
Journal	Geochemical Perspectives Letters
Volume	17
DOIs	https://doi.org/10.7185/geochemlet.2108
Publication status	Published - 18 Feb 2021

Bibliographical note

Funding Information:
We thank the captain and crew of the R/V Pelagia cruise 64PE406, carried out under NESSC programme and financially supported by the Netherlands Ministry of OCW, grant number 024.002.001. We are thankful to B. van der Wagt, P. Laan, M. Klaver, and A. Dickson for analytical support. RH is supported through NWO grant ALW OP.2015.113 awarded to G.-J.R. Constructive comments by Tais Dahl and two anonymous reviewers have helped us to improve our manuscript.

Publisher Copyright:
© 2021 The Authors.

Funding

We thank the captain and crew of the R/V Pelagia cruise 64PE406, carried out under NESSC programme and financially supported by the Netherlands Ministry of OCW, grant number 024.002.001. We are thankful to B. van der Wagt, P. Laan, M. Klaver, and A. Dickson for analytical support. RH is supported through NWO grant ALW OP.2015.113 awarded to G.-J.R. Constructive comments by Tais Dahl and two anonymous reviewers have helped us to improve our manuscript.

Keywords

sapropels
Mediterranean
anoxia
euxinia
Mo-isotopes
molybdenum

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abstract = "Mediterranean sapropels represent some of the largest scale deoxygenation events in recent Earth history. Here, we use high resolutionMo isotope data for seven such events (sapropels S3 to S9) to semi-quantitatively constrain past H2S concentrations using a new interpretive framework. Bottom water H2S was present for all studied sapropels, but the extent of redox changes varied considerably between them, the ultimate driver likely being variations in monsoon strength. Nearquantitative removal of Mo (δ98Mo > 2‰) during deposition of sapropels S5 and S7 suggests predominantly highly sulfidic conditions with long deep water residence times, comparable to the modern Black Sea, whereas considerably lower δ98Mo values for sapropels S3, S4, S8, and S9 (-0.4 to +0.9‰) imply mildly euxinic conditions only (0 ",

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Molybdenum isotope constraints on the temporal development of sulfidic conditions during Mediterranean sapropel intervals

Abstract

Bibliographical note

Funding

Keywords

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