Mechanisms of Late Pleistocene authigenic Fe–Mn-carbonate formation at the Laptev Sea continental slope (Siberian Arctic)

• Published in: arktos
• Main Authors: Logvina, Elizaveta, Krylov, Alexeу, Taldenkova, Еkaterina, Blinova, Valentina, Sapega, Vladimir, Novikhin, Andrey, Kassens, Heidemarie, Bauch, Henning A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2018
• Subjects: Anabar; Arctic; Laptev Sea; khatanga; laptev
• Online Access: https://oceanrep.geomar.de/id/eprint/41902/; https://oceanrep.geomar.de/id/eprint/41902/1/Logvina.pdf; https://doi.org/10.1007/s41063-018-0036-0

Study of the microstructure and isotopic composition of authigenic tubule-shaped carbonate concretions from sediment core PS51/154-11 on the western Laptev Sea continental slope (present water depth 270 m) has allowed for reconstruction of the conditions prevailing during their formation and identification of the mechanisms controlling their genesis. Concretions were collected from the basal sediment unit with an extrapolated age estimate of 16.3–17.6 cal.ka. Crystallization of carbonate tubules occurred at the beginning of the last deglaciation when the site was located in the proximity to the former coastline and the mouths of the Olenek and Anabar-Khatanga rivers in water depths of about 150–170 m. Microprobe analysis showed that the studied carbonate tubules consist of the minerals belonging to the siderite–rhodochrosite isomorphic series. The measured isotopic composition of δ13С and δ18O in the carbonates varies between − 21.0 and − 17.0‰ and between − 9.86 and 1.72‰ VPDB, respectively. The δ18O values in the authigenic carbonates give evidence for the gradual transition from a freshwater affected to modern-like marine sedimentation environment during carbonate crystallization. Water freshening is confirmed by the co-occurrence of authigenic Fe–Mn carbonates and Fe-phosphate vivianite that is a typical mineral of freshwater environments. The dominant source of dissolved inorganic carbon in the pore water was the isotopically light carbon derived from the diagenetic decomposition of organic matter. Two possible scenarios of authigenic carbonates formation are proposed: penetration of freshened ground waters and/or enhanced freshwater influence during short seasonal floods in combination with geochemical processes in a narrow marginal filter zone that was located extremely close to the Laptev Sea continental slope and the studied core site.