Deciphering continental and oceanic climate signals in early Pliocene sediments from the Iberian Margin

The Iberian Margin, including the Portugal Shelf, is a distinctive area in our planet, characterized by a narrow continental shelf where detrital sediments transported by rivers record continental climate patterns. Ocean dynamics in this region are strongly influenced by the Mediterranean Outflow Water (MOW), and the North Atlantic subtropical gyre, both key components of the Atlantic Meridional Overturning Circulation (AMOC) and essential for understanding climate dynamics.

Past research has demonstrated that sedimentary processes from this region are driven by astronomically-forced climatic mechanisms. This study assesses the interaction of continental and oceanic processes along the Iberian Margin during the early Pliocene, an interval of significant palaeoceanographic interest marked by the reestablishment of the MOW after the Messinian Salinity Crisis.

For this, a high-resolution study of calcareous nannofossils assemblages and X-ray fluorescence (XRF) analyses were carried out on sedimentary material retrieved from the 397 IODP expedition (site 1587, southwestern Iberian Margin). Calcareous nannofossils assemblages reveal changes in paleoenvironmental parameters such as productivity and sea surface temperatures, while XRF data indicate changes in continental input.

Based on spectral and wavelet analyses of the XRF data, we identify a robust astronomical signal of precessional origin in the sediments. Moreover, the abundance of Reticulofenestra minuta and Reticulofenestra pseudoumbilicus larger than 7 µm correlates with eccentricity-driven orbital changes. In contrast, Reticulofenestra producta, R. haqii y R. minutula exhibit declining abundance at the base of the Pliocene, suggesting modulation by oceanic mechanisms independent of astronomical forcing. These findings thus evidence the role of orbital-driven climate processes (eccentricity and precession) shaping the continental input. Furthermore, the calcareous nannofossil association reflects distinct ocean dynamics associated to the North Atlantic and processes that determine variability in productivity in the region.