Geochemical composition of Trondheimsfjord surface sediments: Sources and spatial variability of marine and terrigenous components

• Published in: Continental Shelf Research
• Main Authors: Faust, Johan, Knies, Jochen, Slagstad, Trond, Vogt, Christoph, Milzer, Gesa, Giraudeau, Jacques
• Other Authors: University of Tromsø (UiT), Geological Survey of Norway (NGU), University of Bremen, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Trondheimsfjord; Surface sediments; Norway; Fjord environment; Elemental composition; Inorganic organic geochemistry; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Norwegian Sea
• Online Access: https://hal.science/hal-02128917; https://doi.org/10.1016/j.csr.2014.07.008

International audience High sedimentation rates in fjords provide excellent possibilities for high resolution sedimentary and geochemical records over the Holocene. As a baseline for an improved interpretation of geochemical data from fjord sediment cores, this study aims to investigate the inorganic/organic geochemistry of surface sediments and to identify geochemical proxies for terrestrial input and river discharge in the Trondheimsfjord, central Norway. Sixty evenly distributed surface sediment samples were analysed for their elemental composition, total organic carbon (C org), nitrogen (N org) and organic carbon stable isotopes (δ 13 C org), bulk mineral composition and grain size distribution. Our results indicate carbonate marine productivity to be the main CaCO 3 source. Also, a strong decreasing gradient of marine-derived organic matter from the entrance towards the fjord inner part is consistent with modern primary production data. We show that the origin of the organic matter as well as the distribution of CaCO 3 in Trondheimsfjord sediments can be used as a proxy for the variable inflow of Atlantic water and changes in river runoff. Furthermore, the comparison of grain size independent Al-based trace element ratios with geochemical analysis from terrigenous sediments and bedrocks provides evidence that the distribution of K/Al, Ni/Al and K/Ni in the fjord sediments reflect regional sources of K and Ni in the northern and southern drainage basin of the Trondheimsfjord. Applying these findings to temporally well-constrained sediment records will provide important insights into both the palaeoenvironmental changes of the hinterland and the palaeoceanographic modifications in the Norwegian Sea as response to rapid climate changes and associated feedback mechanisms.