Testing the impact of seasonal phytodetritus deposition on δ 13 C of epibenthic foraminifer Cibicidoides wuellerstorfi : A 31,000 year high‐resolution record from the northwest African continental slope

Studies of temporal changes of ocean circulation and deepwater ventilation often rely on δ 13 C records of epibenthic foraminifer Cibicidoides wuellerstorfi . However, primary productivity‐related overprints may distort the signal and simulate a chemical age of ambient water mass that is too old and simulates poorly ventilated ambient bottom waters. To further constrain the use of C. wuellerstorfi δ 13 C records from high‐productivity areas, we analyzed a 14 C AMS ‐dated gravity core from the upwelling regime off northwest Africa at 12°N. We compare this new record with 37 radiocarbon dated δ 13 C records from the eastern Atlantic Ocean between 45°N and 25°S that are bathed by the same water mass. Only during Heinrich events 1 and 2, when the investigated core site off northwest Africa experienced year‐round, sustained deposition of organic matter, the δ 13 C values at this site faithfully record deepwater ventilation states. During times of predominantly seasonal deposition of fresh phytodetritus, however, δ 13 C values were significantly lower than at the reference sites. This underscores that reconstruction of paleocirculation and deep ocean ventilation using C. wuellerstorfi δ 13 C from regions that experienced seasonal phytodetritus deposition needs to be validated by additional proxies that are not affected by local productivity.