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Published on: August 15, 2018
Calcium isotopes link ocean acidification to Aptian-Albian foraminiferal extinctions
Jonathan Chen1, Andrew D Jacobson1, Brian T Huber2
1Department of Earth, Environmental, and Planetary Sciences, Northwestern University, Evanston, IL, USA.
Abstract:
The second-largest extinction event in the evolutionary history of planktic foraminifera occurred at the Aptian-Albian boundary. This extinction may reflect ocean acidification (OA) associated with Oceanic Anoxic Event 1b. As calcium isotope ratios (δ44/40Ca) can track how biocalcification rates respond to OA, we measured δ44/40Ca records for planktic and benthic foraminifera, bulk carbonates, and authigenic calcite across the Aptian-Albian boundary in the South Atlantic. Benthic and bulk δ44/40Ca data display a distinct sequence of negative and positive excursions, similar to δ44/40Ca variations across other OA events. Planktic δ44/40Ca values increase markedly, tracking a reduction in calcification rates coincident with decreases in the size, diversity, and shell thickness of planktic foraminifera. These results suggest that OA drove extinctions of planktic foraminifera at the Aptian-Albian boundary.
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