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Global carbon cycling linked to eustatic changes in the aftermath of the early Aptian Oceanic Anoxic Event (OAE1a)

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he Aptian experienced significant carbon-cycle disruptions, marked by notable paleoclimatic and paleoceanographic shifts. While the mechanisms behind the Aptian oceanic anoxic events (OAE) are relatively well-understood, the interplay between global carbon-cycle dynamics and sea-level changes immediately following the early Aptian OAE1a remains enigmatic. By analyzing a carbonate succession from the western Tethys (eastern Spain), dated using ammonite biostratigraphy as Deshayesites deshayesi and Dufrenoyia furcata zones, we identify a temporal correlation between a sea-level highstand and a subsequent fall, aligning respectively with a global carbon-isotope excursion exceeding +4‰, unprecedented in the Cretaceous, and a sharp negative isotopic shift from +4.3‰ to −0.7‰. The concurrence of these sea-level fluctuations and carbon isotope variations across multiple regions underscores the eustatic origin of sea-level change and its profound impact on global carbon cycling. We propose that during highstand and transgressive stages, sea expansion acted as a carbon sink, facilitating the increased burial of isotopically light carbon. Conversely, rapid sea-level falls likely triggered sediment reworking, reintroducing this light carbon into the dissolved inorganic carbon (DIC) of the global ocean. This study highlights the overlooked role of remobilized sediments as a source of carbon during the Aptian, commonly attributed to volcanic degassing, and emphasizes the immediate and significant response of the carbon cycle to eustatic changes.

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Global and Planetary Change, 2026, vol. 263

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cc-by (c) Muñoz López, Daniel et al., 2026

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Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

# metadata.dc.title[].value
Global carbon cycling linked to eustatic changes in the aftermath of the early Aptian Oceanic Anoxic Event (OAE1a)