Tracking Variability in Atmospheric, Oceanic, and Riverine Inputs to the Iberian Margin Over the Last 250 kyr

Abstract

Abstract The Iberian Margin provides an exceptional archive of climate variability due to its high sedimentation rates. However, uncertainties persist regarding the provenance of terrigenous detrital sediments on the Iberian Margin, and the climate‐driven changes in their source areas and transport processes. By integrating clay mineralogy with grain‐size data and end‐member modeling for IODP Site U1588 sediments, we characterize terrigenous detrital inputs to the southwestern Iberian Margin and reconstruct their orbital‐scale variations over the last ∼250 kyr. Three sources of sediment supply are identified. (I) Fine‐grained Iberian riverine inputs: rich in smectite (61%) and poor in kaolinite (7%) and chlorite (7%); (II‐A) Saharan dust: rich in illite (49%) with low kaolinite and smectite, consistent with the silt‐sized mode; (II‐B) Sahelian dust: richest in kaolinite (22%) with high smectite, reflecting additional aeolian source; and (III) Mediterranean Outflow Water‐transported particles: rich in chlorite (22%) with intermediate levels of other clay minerals, co‐varying with the sortable‐silt fraction. Our end‐member modeling results indicate North African dust as a major source for Iberian Margin sediments, as supported by spatiotemporal variations in the illite/kaolinite (I/K) ratio. Illite mineralogy further reveals a marked contrast across the glacial‐interglacial cycles. Relative to the last glacial cycle (∼130–0 ka), the penultimate cycle (∼250–130 ka) shows higher illite contents and I/K ratios, weaker chemical weathering, and pronounced precessional cyclicity. This contrast suggests a long‐term contraction of North African dust sources, expressed as reduced Saharan input during the last glacial cycle, and likely caused by a northward displacement of the Intertropical Convergence Zone.