Manganese cycles in Quaternary sediments of the Arctic Ocean - Climatic signals or diagenesis?
Final Report Abstract
In Quaternary deposits of the Arctic Ocean, brown Mn-rich layers are well-known, widespread, but also debated features. We applied inorganic geochemical analyses to sediment cores from the western Arctic Mendeleev Ridge (RV Polarstern Expedition ARK-XXIII/3) and the central Arctic Lomonosov Ridge (IODP Expedition 302). Our results show that a) most brown layers are associated with detrital (icerafted) and biogenic carbonate enrichments, b) all Mn-rich layers are enriched in Fe (oxyhydr)oxides and Co, Cu, Mo and Ni scavenged by Mn/Fe (oxyhydr)oxides, and c) distinct bioturbation patterns (i.e., brown burrows into the underlying sediments) suggest these metal enrichments formed close to the sediment–water interface. We infer that the metal-rich layers formed under warmer (interglacial/interstadial) conditions with an intensified continental hydrological cycle and only seasonal sea ice cover. Metals were delivered to the Arctic Ocean by rivers/sea ice/coastal erosion, while seasonal productivity increased the reactive organic matter export to the sea floor. The coeval deposition of organic matter and Mn/Fe (oxyhydr)oxides triggered an intense diagenetic Mn and Fe cycling at the sediment-water interface. These climate-induced primary and secondary processes resulted in the enrichments of Mn/Fe (oxyhydr)oxides, scavenging of trace metals, and the degradation of labile organic matter. With the onset of glacial/stadial conditions, the riverine/erosive delivery of metals strongly decreased, a solid sea ice cover terminated the production and export of fresh organic matter, and gray-yellowish sediments with lower metal contents were deposited. Our data do not support glacial/stadial bottom water oxygen depletion that might have affected the Mn distribution. Despite the climatic control on the composition of the brown layers, pore water data show that diagenetic redistribution of Mn and Mo is still affecting the deeper sediments. The degree of Mn remobilisation (potentially causing complete dissolution of existing, and formation of new Mn layers) largely depends on the availability and reactivity of Mn and organic matter. The different responses of adsorbed trace metals, in particular Mo and Co, to Mn diagenesis might serve as a way to quantify the diagenetic overprint individual Mn layers experienced, but additional systematic analyses are required to support this hypothesis. Without doubt, the findings of this study provide valuable insights into the use of Mn-rich layers as stratigraphic marker horizons in Arctic marine sediments, particularly in the frame of tentative future IODP expeditions to the Arctic Ocean.
Publications
- Geochemical cycles in Arctic marine sediments - Climate signals or diagenesis? NSG/EUROPROX Symposium, Utrecht, 28.11.2008
C. März, B. Schnetger, H.-J. Brumsack
- Inorganic geochemistry of Arctic (Plio- /Pleistocene) sediments - From Lomonosov Ridge to Bering Sea. Geochimica Actie (Geochemical Seminar), Utrecht University, 04.06.2009
C. März, B. Schnetger, H.-J. Brumsack
- Major and minor element signatures and their paleoenvironmental significance in Central Arctic Ocean sediments (Lomonosov Ridge, IODP Leg 320). IODP/ICDP Kolloquium, Potsdam, 16.- 18.03.2009
C. März, B. Schnetger, H.-J. Brumsack
- Manganese cycles in Arctic Ocean sediments - Climate signals or diagenesis? European Geosciences Union (EGU) General Assembly, Vienna, 19.-25.04.2009
C. März, A. Stratmann, S. Eckert, B. Schnetger, H.-J. Brumsack
- Manganese diagenesis in Arctic Ocean sediments – Stratigraphic and paleoenvironmental implications. IODP/ICDP Kolloquium, Potsdam, 16.-18.03.2009
C. März, A. Stratmann, S. Eckert, B. Schnetger, H.-J. Brumsack
- (2010) Paleoenvironmental implications of Cenozoic sediments from the Central Arctic Ocean (IODP Expedition 302) using inorganic geochemistry. Paleoceanography 25, PA3206
C. März, B. Schnetger, H.-J. Brumsack
(See online at https://doi.org/10.1029/2009PA001860) - What can inorganic geochemical records tell us about the history of the Arctic Ocean? UK Polar Network, Polar sedimentary processes and archives workshop, Loughborough, 18.-19.11.2010
C. März, B. Schnetger, H.-J. Brumsack
- (2011): Das Marine Sediment als Gedächtnis des Klimas (The marine sediments as long-term climate archive), in: J. Lozán (Ed.) Warnsignale Klima: Die Meere - Änderungen und Risiken
C. März, P. Böning, H.-J. Brumsack
- (2011): Manganese-rich brown layers in Arctic Ocean sediments: Composition, formation mechanisms, and diagenetic overprint. Geochim. Cosmochim. Acta. 75, 7668-7687
C. März, A. Stratmann, J. Matthiessen, A.-K. Meinhardt, S. Eckert, B. Schnetger, C. Vogt, R. Stein, H.-J. Brumsack
- Metal-rich brown layers in Arctic Ocean sediments: Climate versus diagenesis. Goldschmidt Conference 2011, Prague, 15.-19.08.2011
C. März, A. Stratmann, S. Eckert, B. Schnetger, S.W. Poulton, H.-J. Brumsack
- More than just "brown layers": Manganese enrichments in Quaternary Arctic Ocean sediments. Session CL 1.3, European Geosciences Union (EGU) General Assembly, Vienna, 22.-27.04.2012
C. März, A. Stratmann, J. Matthiessen, S.W. Poulton, A.-K. Meinhardt, S. Eckert, B. Schnetger, C. Vogt, R. Stein, H.-J. Brumsack
- More than just “brown layers”: Manganese in Quaternary Arctic Ocean sediments. Goldschmidt Conference 2012, Montreal, 24.-29.06.2012
C. März, A. Stratmann, J. Matthiessen, S.W. Poulton, A.-K. Meinhardt, S. Eckert, B. Schnetger, C. Vogt, R. Stein, H.-J. Brumsack
