Marz, Christian et al. (2011): Variable Eocene-Miocene sedimentation processes and bottom water redox conditions in the central Arctic Ocean (IODP Expedition 302)

Leg/Site/Hole:
IODP 302
Identifier:
2012-024345
georefid

10.1016/j.epsl.2011.08.025
doi

Creator:
Marz, Christian
University of Oldenburg, Institute for Chemistry and Biology of the Marine Environment, Oldenburg, Germany
author

Vogt, Christoph
University of Bremen, Germany
author

Schnetger, Bernhard
author

Brumsack, Hans-Juergen
author

Identification:
Variable Eocene-Miocene sedimentation processes and bottom water redox conditions in the central Arctic Ocean (IODP Expedition 302)
2011
Earth and Planetary Science Letters
Elsevier, Amsterdam, Netherlands
310
3-4
526-537
In 2004, Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition, ACEX) to the Lomonosov Ridge drilled the first Central Arctic Ocean sediment record reaching the uppermost Cretaceous ( approximately 430 m composite depth). While the Neogene part of the record is characterized by grayish-yellowish siliciclastic material, the Paleogene part is dominated by biosiliceous black shale-type sediments. The lithological transition between Paleogene and Neogene deposits was initially interpreted as a single sedimentological unconformity (hiatus) of approximately 26 Ma duration, separating Eocene from Miocene strata. More recently, however, continuous sedimentation on Lomonosov Ridge throughout the Cenozoic was proclaimed, questioning the existence of a hiatus. In this context, we studied the elemental and mineralogical sediment composition around the Paleogene-Neogene transition at high resolution to reconstruct variations in the depositional regime (e.g. wave/current activity, detrital provenance, and bottom water redox conditions). Already below the hiatus, mineralogical and geochemical proxies imply drastic changes in sediment provenance and/or weathering intensity in the hinterland, and point to the existence of another, earlier gap in the sediment record. The sediments directly overlying the hiatus (the Zebra interval) are characterized by pronounced and abrupt compositional changes that suggest repeated erosion and re-deposition of material. Regarding redox conditions, euxinic bottom waters prevailed at the Eocene Lomonosov Ridge, and became even more severe directly before the hiatus. With detrital sedimentation rates decreasing, authigenic trace metals were highly enriched in the sediment. This continuous authigenic trace metal enrichment under persistent euxinia implies that the Arctic trace metal pool was renewed continuously by water mass exchange with the world ocean, so the Eocene Arctic Ocean was not fully restricted. Above the hiatus, extreme positive Ce anomalies are clear signs of a periodically well-oxygenated water column, but redox conditions were highly variable during deposition of the Zebra interval. Significant Mn enrichments only occur above the Zebra interval, documenting the Miocene establishment of stable oxic conditions in the Arctic Ocean. In summary, extreme and abrupt changes in geochemistry and mineralogy across the studied sediment section do not suggest continuous sedimentation at the Lomonosov Ridge around the Eocene-Miocene transition, but imply repeated periods of very low sedimentation rates and/or erosion. Abstract Copyright (2011) Elsevier, B.V.
English
Serial
Coverage:Geographic coordinates:
North:87.5600
West:136.1000East: 139.3300
South:87.5100

Stratigraphy; Sedimentary petrology; anaerobic environment; Arctic Coring EXpedition; Arctic Ocean; bottom water; Cenozoic; cerium; depositional environment; diagenesis; Eh; Eocene; Expedition 302; geochemical anomalies; ICP mass spectra; Integrated Ocean Drilling Program; Lomonosov Ridge; marine sediments; mass spectra; metals; Miocene; Neogene; Paleogene; provenance; rare earths; sedimentation; sedimentation rates; sediments; spectra; Tertiary; trace metals; unconformities; weathering;

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