A NEW CHRONOLOGICAL CONCEPT FOR THE EASTERN ARCTIC OCEAN
KNIES, JOCHEN . Geological Survey of Norway.
Matthiessen, Jens . Alfred Wegener Institute for Polar and Marine Research.
Nowaczyk, Norbert . GeoForschungsZentrum Potsdam.
Stein, Ruediger . Alfred Wegener Institute for Polar and Marine Research.
Vogt, Christoph . University of Bremen.
Wollenburg, Jutta . Alfred Wegener Institute for Polar and Marine Research.
Problems and constrains in dating late Quaternary Arctic Ocean sediments
Studies on sedimentary records from the central and eastern Arctic Ocean with sedimentation rates up to ~3 cm/ka have highlighted the tremendous impact of the Arctic Ocean freshwater budget on world climate during major deglacial phases, i.e. the last glacial/interglacial and the marine oxygen isotope (MIS) 4/3 transition. However, the sometimes enigmatic and discontinuous stable oxygen isotope records limit the precision of paleoenvironmental interpretations. Various approaches including sedimentological, physical and –micropaleontological methods have been applied to establish a chronostratigraphy but low preservation and discontinuous records of biogenic material and equivocal interpretations of paleomagnetic and radionuclide records limit the stratigraphic resolution of the different methods.
Multi-proxy stratigraphic concept
Our new strategy for tackling these ongoing chronostratigraphic problems integrates various chronostratigraphic approaches to date records from the marginal eastern Arctic Ocean that underlies the submerging Atlantic-water derived intermediate waters (Fig. 1). We chose the Yermak Plateau – the Atlantic/Arctic Ocean gateway – as key area for our study because, (1) here, rather than in central Arctic Ocean, carbonate bearing sequences permit establishment of a relatively continuous stable oxygen isotope stratigraphy, which is still the prerequisite for any subsequent application of chronological approaches, and (2) the dynamic coupling between the northernmost branch of the Gulf Stream and the Arctic Ocean – possibly one of the decisive factors controlling rapid climate changes – is best studied in our key area. Once the records are exactly dated, they may provide useful stratigraphic reference sections for central Arctic Ocean records underlying the submerging Atlantic-water derived intermediate waters. We have selected three locations of high priority (PS2138, PS1533, PS1535) and two locations of lower priority (PS2837, PS2123). At these sites previous studies have shown that a well-constrained chronostratigraphy can be established but, unfortunately, almost no core material is left for additional studies (Fig. 1). Our main goal is to strengthen the reliability of Arctic Ocean chronology and establish a new, fundamental basis for generating high-resolution paleoenvironmental reconstructions in the Arctic Ocean.
Sediment core PS2138 as one example
The chronology in core PS2138 recovered from the marginal eastern Arctic Ocean is based on the oxygen isotope stratigraphy performed on planktic and benthic foraminifera, 24 AMS14C dates back to 31 14C ka B.P., geomagnetic excursions, radioistopic signals, micropaleontological evidences and deduced paleoproductivity fluctuations as well as the correlation of ice rafted debris (IRD) events to the polar marine events in the North Atlantic. The bulk of direct and indirect age tie points available from this record over the past 150.000 years highly strengthens the reliability of paleoenvironmental reconstruction in the area even on timescales <1000 years.
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