High rates of organic carbon burial in submarine deltas maintained on geological timescales

Sophie Hage, Brian W. Romans, Thomas G. E. Peploe, Miquel Poyatos-Moré, Omid Haeri ardakani, Daniel Bell, Rebecca G. Englert, Sebastian A. Kaempfe-Droguett, Paul R. Nesbit, Georgia Sherstan, Dane P. Synnott, Stephen M. Hubbard

Research output: Contribution to journalArticleResearchpeer-review

1 Citation (Scopus)

Abstract

Burial of terrestrial organic carbon in marine sediments can draw down atmospheric CO2 levels on Earth over geologic timescales (≥105 yr). The largest sinks of organic carbon burial in present-day oceans lie in deltas, which are composed of three-dimensional sigmoidal sedimentary packages called clinothems, dipping from land to sea. Analysis of modern delta clinothems, however, provides only a snapshot of the temporal and spatial characteristics of these complex systems, making long-term organic carbon burial efficiency difficult to constrain. Here we determine the stratigraphy of an exhumed delta clinothem preserved in Upper Cretaceous (~75 million years ago) deposits in the Magallanes Basin, Chile, using field measurements and aerial photos, which was then combined with measurement of total organic carbon to create a comprehensive organic carbon budget. We show that the clinothem buried 93 ± 19 Mt terrestrial-rich organic carbon over a duration of 0.1–0.9 Myr. When normalized to the clinothem surface area, this represents an annual burial of 2.3–15.7 t km−2 yr−1 organic carbon, which is on the same order of magnitude as modern-day burial rates in clinothems such as the Amazon delta. This study demonstrates that deltas have been and will probably be substantial terrestrial organic carbon sinks over geologic timescales, a long-standing idea that had yet to be quantified.
Original languageEnglish
Pages (from-to)919-924
Number of pages6
JournalNature Geoscience
Volume15
Issue number11
DOIs
Publication statusPublished - 24 Oct 2022

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