Radiogenic isotopes for deciphering terrigenous input provenance in the western Mediterranean

• Published in: Chemical Geology
• Main Authors: Rodrigo-Gámiz, M., Martínez-Ruiz, F., Chiaradia, Massimo, Jiménez-Espejo, F.J., Ariztegui, Daniel
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: info:eu-repo/classification/ddc/550; North Atlantic
• Online Access: https://archive-ouverte.unige.ch/unige:73281

Radiogenic isotopic signatures in marine sediments can be used to trace terrigenous source areas and transport mechanisms, which are in turn related to climate variability. To date, most of the published studies using this approach have been focused on eastern Mediterranean sediments. In contrast, we study here the terrigenous input provenance in the westernmost Mediterranean (Alboran Sea basin) by using radiogenic isotope proxies and Nd model ages in a marine record spanning the last 20 ka. Nd, Sr and Pb isotopes, obtained from carbonate-free samples from the < 37μm size fraction, were used to characterize terrigenous variations, including eolian input. Substantial shifts in Pb isotopic signatures throughout the studied time interval reveal a change from North African dominated sources during the glacial period to European dominated sources during the Holocene. Nd and Sr shifts likewise indicate two main short-term changes in sediment provenance, during the last Heinrich event and the early-middle Holocene transition (ca. 8.9 ka cal. BP). Nd model ages over 1.45 Ga also support a contribution of an older component in the terrigenous source, likely Archaean material from the present Senegal region, during both periods. Conversely, terrigenous material mainly shows a dominant provenance from present-day Morocco, Mali, Mauritania, Niger, and Algeria, mixed with material from southern Iberia and southern France. Source variations in the westernmost Mediterranean were mainly driven by fluctuations in wind intensity and fluvial discharges. These fluctuations seem to have been modulated by the African monsoon system further conditioned by the ITZC migrations and the position of the North Atlantic anticyclone system.