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Abstract: The Paleocene–Eocene Thermal Maximum (PETM), a hyperthermal event that occurred ca. 56 Ma, has been attributed to the release of substantial amounts of carbon, affecting the atmosphere, biosphere and the oceans. Current issues with respect to our understanding of the PETM include the amount of carbon released, the duration of carbon release, and the mechanism(s) of release, all of which are related to the magnitude and profile of the associated Carbon Isotope Excursion (CIE). High-resolution organic carbon profiles ( ) of six PETM sections in northern Spain are presented that span a transect from continental to marine environments. These data represent the highest-resolution isotope records for these sections and allow a comparison of the magnitude of the excursion, the shape of the vertical profile during the PETM episode, and the relative timing of the onset of the excursion across a linked sediment routing system. Previous studies using carbonate data have suggested that the continental Claret Conglomerate, found in this region, formed synchronously with a marine clay-rich siliciclastic unit, with these key lithological changes interpreted to be driven by increased seasonal rainfall-runoff in the warmer PETM climate. Our data suggest that deposition of these units did not immediately follow the CIE onset, indicating that there may be a temporal lag between the onset of the PETM warming and the response of the depositional systems in northern Spain. No systematic variation in the magnitude of the CIE between different depositional environments was found; the marine CIE magnitudes are at the higher end of those previously described ( ), and the continental ranges are lower ( ). [Copyright &y& Elsevier]

The micronutrient iron (Fe) plays a fundamental role controlling primary productivity in the upper ocean, with volcanic eruptions and deposition of airborne volcanic material (termed tephra) a potential source of Fe. Here, we investigate the geochemical and Fe isotopic (δ 56 Fe) composition of tephra layers, sediments, and mixed tephra-sediment samples from the Integrated Ocean Drilling Program (IODP) Hole 1396C, located offshore the volcanically active island of Montserrat in the Lesser Antilles, Caribbean Sea. We find that buried tephras, which have experienced diagenesis, exhibit lighter δ 56 Fe (relative to standard IRMM-524a) compositions (down to −0.26 ± 0.04‰, 2SD) than fresh tephra deposited in Montserrat (δ 56 Fe = 0.02 ± 0.02‰, 2SD). Such negative values suggest that isotopically heavier Fe has been lost from the originally deposited material. Using multivariate statistical modelling and mass balance constraints, we identify the outward Fe flux (with calculated δ 56 Fe of 0.21 ± 0.31‰, 2SD, n = 12) during non-reductive dissolution of tephra as the likely cause of the retention of these light δ 56 Fe compositions. Due to the widespread nature of tephra deposition, tephra diagenesis may provide an important source of isotopically heavy dissolved Fe (dFe) to the oceans. This process contrasts with more commonly considered reductive dissolution processes, which provide a source of dFe enriched in light isotopes to the oceans. • An iron isotope record is reported for archived tephra in the Caribbean Sea. • On average, 29% of all marine sediment in the Caribbean Sea is tephra. • Buried tephras have lighter Fe isotope composition than fresh tephra. • Diagenetic loss of iron by non-reductive dissolution is evidenced by isotope mass-balance. • Tephra diagenesis and dissolution may be important for seawater budgets. [ABSTRACT FROM AUTHOR]