Using Stable Isotopes to Disentangle Marine Sedimentary Signals in Reactive Silicon Pools

Summary, in English

Many studies use sedimentary biogenic silica (bSiO₂) stable isotopes (e.g., δ³⁰Si) as paleoproxies but neglect signals from other sedimentary reactive SiO₂ phases. We quantified δ³⁰Si for multiple reactive Si pools in coastal river-plume sediments, revealing up to −5‰ difference between acid-leachable and alkaline-digestible amorphous SiO₂. Thus, previous studies have missed valuable information on early diagenetic products and, in cases where sediments were not cleaned, potentially biased bSiO₂ δ³⁰Si values. Acid-leachable δ³⁰Si, that is, from authigenic products, are the result of either multistep fractionation from a bSiO₂ source or an ~2‰ fractionation (consistent with metal hydroxide formation) from slowly dissolving lithogenic SiO₂. This analysis also suggests that sedimentary diatom bSiO₂, which has increased regionally in the last half-century, is the critical substrate of early authigenic Si precipitates. Regional eutrophication, which has stimulated sedimentary bSiO₂ accumulation, may have facilitated additional sequestration of both sedimentary Si and cations from early diagenetic products.

• Author: Rebecca A. Pickering; Lucie Cassarino; Katharine R. Hendry; Xiangli L. Wang; Kanchan Maiti; Jeffrey W. Krause
• Publishing year: 2020-08-16
• Language: English
• Publication/Series: Geophysical Research Letters
• Volume: 47
• Issue: 15
• Links: http://dx.doi.org/10.1029/2020GL087877
• Document type: Journal article
• Publisher: American Geophysical Union (AGU)
• Topic: Oceanography, Hydrology, Water Resources
• Keywords: authigenic coatings; biogenic silica; early diagenesis; Gulf of Mexico; reactive silicon; stable silicon isotopes
• Status: Published
• ISBN/ISSN/Other: ISSN: 0094-8276