Calcareous nannofossils are abundant biogenic carbonate particles in the oceanic fossil record, playing a key role in paleoceanographic studies. Despite this importance, the potential of calcareous nannofossils for analysing contourite sediments has received limited attention. It was previously thought that the taphonomic alterations caused by contour currents seriously compromised the use of nannofossil assemblages as reliable paleoenvironmental indicators. Here, we examine how calcareous nannofossils respond to contour current activity as sedimentary entities and evaluate their reliability as paleoenvironmental indicators within the Contourite Depositional System of the Gulf of Cadiz. To achieve this, we employed a multi proxy approach comparing absolute nannofossil abundances with Zr/Al ratios (a proxy for bottom current intensity) and ichnological data to constrain seafloor depositional processes. Additionally, relative nannofossil abundances were compared with diatom and phytolith records to characterize upper water column conditions. The Gulf of Cadiz is considered a natural laboratory for understanding contour current dynamics. We analyse samples from the IODP 339 Expedition hole U1387C, which belong to the Early Pliocene. We observed abrupt minimums in absolute nannofossil abundances during intervals of peaks in the Zr/Al ratio, associated with intense Mediterranean Outflow Water influence. However, our results indicate that this phenomenon affects the entire nannofossil assemblage of uniformly regardless of size. Consequently, relative abundances remain unaltered even under intense bottom current conditions, reliably preserving the original paleoenvironmental signal. This study also enables the reconstruction of Mediterranean Outflow Water dynamics in the Gulf of Cadiz during the Early Pliocene. • Nannofossils can play a fundamental role in the study of contourite sediments. • Nannofossil absolute abundances inversely correlate with current intensity proxies. • Taphonomically, winnowing alters calcareous nannofossil abundance but not percent composition. • Nannofossil percent composition record paleoenvironmental signals in contourites.
Martín-García et al. (Fri,) studied this question.