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Ehlert, Claudia; Doering, Kristin; Wallmann, Klaus; Scholz, Florian; Sommer, Stefan; Grasse, Patricia; Geilert, Sonja; Frank, Martin (2016): Age models for sediment cores M77/1-470-MUC29, M77/1-449-MUC19 and M77/1-459-MUC53 from the Peruvian shelf at 11°S. PANGAEA,, Supplement to: Ehlert, C et al. (2016): Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation. Geochimica et Cosmochimica Acta, 191, 102-117,

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Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm−2 yr−1. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.
German Science Foundation (DFG), grant/award no. 27542298: Climate - Biogeochemistry Interactions in the Tropical Ocean
Median Latitude: -10.999718 * Median Longitude: -78.194495 * South-bound Latitude: -11.000500 * West-bound Longitude: -78.521160 * North-bound Latitude: -10.996830 * East-bound Longitude: -77.943330
Date/Time Start: 2008-11-03T19:40:00 * Date/Time End: 2008-11-13T01:43:00
The age model for core 470-MUC29 has been published and described in detail in Ehlert et al. (2015). Based on correlation with other cores from the region using 210Pb datings and sediment properties (opal concentrations, sediment density, etc.), the sedimentation rate varies between 1.8 mm yr-1 in the upper part and 0.6 mm yr-1 in the deeper part. Therefore, the core covers the past ca. 550 years, and therefore the Modern Warm Period (MWP, 1870AD - present), the Transition Period (TP, 1820 - 1870AD) and the Little Ice Age (LIA, 1400 - 1820AD).
The age model of core 449-MUC19 was estimated using 210Pb datings. Assuming a constant sedimentation rate of 0.5 mm yr-1, the core covers the past ca. 1000 years and therefore reaches back to the Medieval Climatic Anomaly (MCA, ca. 800 - 1250AD)
Core 549-MUC53 has an average sedimentation rate of 0.58 mm yr-1 (based on 210Pb dating), and covers the time period from the LIA until Present .
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