Plant biomarkers and elemental compositions reveal transport changes on the Iberian margin across the late Neogene

To reconstruct Iberian Margin paleoclimate and the effects of Mediterranean gateway restriction during the late Miocene, International Ocean Discovery Program Expedition 401 drilled Site U1609 on the southwestern Portuguese Margin (37º22.6259’N, 9º35.9120’W; 1660 m water depth) in the path of Mediterranean Overflow Water (MOW). We present a multiproxy study of plant waxes, lignin phenols, palynomorphs, and X-ray fluorescence. From 11.5–9.5 Ma, hemipelagic sediments have high Ca and dinoflagellate:pollen ratios. Between 9.5 and 6 Ma plant proxies (e.g., alkanes and lignin) and terrigenous elements (e.g., Ti) become more abundant, with more land-based flux attributed to tectonic uplift and the initiation of MOW. Sediments from 6–2.5 Ma indicate relatively stable elemental proportions, although precessional pacing of Ti/Ca occurs throughout the record. Plant wax n -alkane δ 13 C and δD values indicate C 3 vegetation and Atlantic storm tracks, like modern, occurred throughout the warmer Tortonian–Zanclean climates. In contrast, lignin indicates greater variability across the record. High lignin transport and low syringyl/vanillyl ratio suggest riverine export from high-elevation conifer forests in the SE Iberian Peninsula, followed by lateral ocean current transport transport, with fluxes increasing as MOW strengthened at 4.5 Ma. During the Messinian Salinity Crisis, when MOW ceased, lignin delivery was reduced and restricted to lowland riverine inputs from SW Iberia, where angiosperms today dominate the exported woody biomass. We find river-exported gymnosperm lignin to be a valuable tracer of distal advection tracking the history of MOW across the Messinian gateway reorganization.