The Mesozoic-Cenozoic climate history of the Alpha-Mendeleev Ridge – AMEX 2008
The tectonic evolution as well as the paleoclimatic history of the central Arctic Ocean during Mesozoic-Early Cenozoic times is purely known. In this context, a major break-through was the recent very successful IODP drilling campaign on Lomonosov Ridge (Arctic Ocean Drilling Expedition - ACEX; Moran et al., 2006). For the Alpha-Mendeleev Ridge, however, no long-term, complete paleoclimatic records are available yet. During RV “Polarstern” Expedition ARK-XIV/1a (Jokat et al., 1999) and the “HOTRAX” Expedition (Darby et al., 2005) a couple of undisturbed sedimentary records were obtained on the Alpha Ridge, probably representing the Quaternary time interval. In only four short cores taken from drifting ice islands on the Alpha Ridge, older pre-Neogene, partly organic-carbon-rich (“black-shale type”) sediments were recovered (Fig. 1; Jackson et al., 1999; Clark et al., 1986; Firth and Clark, 1998). In general, these data suggest a warmer (ice-free) Arctic Ocean with strong seasonality and high paleoproductivity, most likely associated with upwelling conditions. Differences in sediment composition between the cores may have been caused by lateral and temporal nutrient conditions, oceanic currents, bottom-water oxygen levels, and basin topography. Detailed reconstructions of the long-term paleoenvironmental history from the Alpha-Mendeleev Ridge area representing the transition from Mesozoic-Early Tertiary Greenhouse conditions to upper Tertiary-Quaternary Icehouse conditions, however, are still needed. In addition, high-resolution, well-dated records representiating the late Quaternary (postglacial-Holocene) climate history are also absent from this permanently ice-covered region.
Thus, the overall goals of our marine-geological research program based on material to be taken during the “Polarstern” Expedition 2008 (Fig. 2) and part of the IPY Program, are (1) high-resolution studies of changes in paleoclimate, paleoceanic circulation, paleoproductivity, and sea-ice distribution in the central Arctic Ocean and the adjacent continental margin during Late Quaternary (especially postglacial-Holocene) times, and (2) the long-term history of the Mesozoic and Cenozoic Arctic Ocean and its environmental evolution from a warm to an ice-covered polar ocean. In areas such as the Alpha-Mendeleev-Ridge, pre-Quaternary sediments are cropping out, which could even be cored with coring facilities aboard “Polarstern” and which would allow to study the Mesozoic/Tertiary history of the (preglacial) Arctic Ocean.
Sampling should be performed on transects from the Canada Basin across the Alpha-Mendeleev Ridge into the Makarov Basin. Of interest are areas of high sedimentation rates for the high-resolution studies of late Quaternary (postglacial-Holocene) paleoenvironment and areas where older strata are cropping-out (for studying Mesozoic/Cenozoic sequences of paleoenvironmental change). Coring positions have to be collected carefully using detailed bathymetric mapping and sub-bottom profiling systems (e.g., Hydrosweep, Parasound) to avoid areas of sediment redeposition (turbidites and slumps) and erosion, and to identify areas where older sediments are cropping out.
The proposed “Polarstern”-Expedition 2008 (AMEX) which is composed of a geophysics program dealing with seismic site survey aspects and a geology program, will be part of an international approach. The geological and seismic data to be obtained during the “Polarstern” Expedition 2008 will be the base for a more precise planning of a future international (German, Norwegian, Danish, and Korean) scientific drilling within the Integrated Ocean Drilling Program (IODP).
The post-cruise research to be carried-out on AMEX material, will comprise:
- Stratigraphy of the sedimentary sequences (approach: oxygen and carbon stable isotopes, absolute age dating, paleomagneto-stratigraphy, biostratigraphy, natural radionuclides, magnetic susceptibility, correlation to other existing (dated) Arctic Ocean records; etc.)
- Terrigenous sediment supply and climate-related variability (approach: MSCL-logging and XRF-scanning records; bulk-, clay- and heavy-mineral assemblages; grain-size distribution; major, minor and rare earth elements; etc.)
- Organic- and inorganic-geochemical records and paleoenvironmental change, i.e., reconstruction of marine/terrigenous organic-carbon sources; sea-surface temperature, salinity, and productivity; water-mass anoxia; sea-ice cover; continental vegetation (approach: oxygen and carbon stable isotopes; organic-geochemical bulk parameters; maceral composition; biomarker composition; compound-specific carbon and hydrogen isotopes; TEX86 and Uk37 indices; major, minor and rare earth elements etc.)
- Marine biota and paleoenvironmental change (approach: foraminifers, diatoms, radiolarians, coccolithophorids, palynomorphs etc.)
Fig. 1: (A) Map with location of sediment cores FL422, FL437, FL533, and CESAR-6 on the Alpha Ridge; (B) Reconstruction of the Late Cretaceous Arctic Ocean (from Smith 1987; Lawver and Scotese 1990). AR Alpha Ridge, SB Svalbard, NSI New Siberian Islands, GRN-NAM pole of opening for Greenland-North America; (C) Organic carbon, hydrogen index and oxygen index data and lithologies of the lowermost Early Maastrichtian section of Core FL533 (data from Clark et al. 1986; Firth and Clark 1998).
Fig. 2: Proposed working area of "Polarstern" Expedition 2008
AWI Participants
Wilfried Jokat (chief-scientist of “Polarstern”-Expedition 2008; geophysics)
External collaborators
Hans Brumsack (ICBM Oldenburg)
Thomas Frederichs (Bremen University)
Robert Spielhagen (IFM-GEOMAR Kiel)
Christoph Vogt (Bremen University)
Seung-il Nam (Korean Institute of Geoscience and Mineral Resources)
Vladimir Shevchenko (IORAS Moscow)
Michael Levitan (GEOKHI Moscow)
Funding
AWI
References
Clark, D.L., Byers, C.W., Pratt, L. M., 1986. Cretaceous black mud from the Central Arctic Ocean. Palaeoceanography 1(3), 265-271.
Firth, J.V., Clark, D.L., 1998. An early Maastrichtian organic-walled phytoplankton cyst assemblage from an organic-rich black mud in Core FL-533, Alpha Ridge: evidence for upwelling conditions in the Cretaceous Arctic Ocean. Marine Micropaleontology 34, 1-27.
Jackson, H.R., Mudie, P.J., Blasco, S.M., 1985. Initial geological report on CESAR - The Canadian Expedition to study the Alpha Ridge, Arctic Ocean. Geological Survey of Canada Paper 84-22, 177 pp.
Jokat, W., Stein, R., Rachor, E., Schewe, I., and the Shipboard Scientific Party, 1999. Expedition Gives Fresh View of Central Arctic Geology. EOS, 80 (40): 465-473.
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