Paleointensity Confirms cm-scale Sedimentation Rates and Suggests Intervals with Non-uniform Deposition on the Lomonosov Ridge, Central Arctic Ocean

Abstract

Chronologies of Arctic Ocean Plio-Pleistocene sediments have been mainly based on paleomagnetic reversal stratigraphy due to low microfossil-content that precludes biostratigraphic dating methods and establishment of an oxygen isotope stratigraphy. Paleomagnetic reversal records primarily from Canadian Basin sediment cores, but also from other Arctic Ocean cores, were initially interpreted as polarity reversals (chron/sub-chron) because paleomagnetic excursions have not until recently been accepted as expressions of genuine geomagnetic features. A Geomagnetic Excursion Time Scale (GETS) has not yet been established and, therefore, the use of excursions as a dating tool is largely dependent on external time control. A number of cores from different regions of the Arctic Ocean have recently been dated interpreting short polarity reversal intervals as geomagnetic excursions. Some of these data reveal narrow intervals with complex patterns of short normal/reversed zones and also absence of excursions at 'expected' depths. Although these observations may be attributed to the short duration of geomagnetic excursions, intermittent bioturbation (?) or other erasing processes, they clearly demonstrate the need for an independent dating control confirming uniformity of accumulation. Paleointensity-records could convey reliable data for relatively high-resolution dating that may disclose variations in rate and uniformity of sedimentation. We present paleointensity records from cores from the Lomonosov Ridge with cm-scale sedimentation rates that carry records of inferred excursions. One of the cores has been dated correlating MnO enriched brown colored layers with interglacial cycles, biostratigraphic marker horizons and excursions (Jakobsson et al, 20001). The absence of excursions in the upper parts of the cores remains unaccounted for. Paleointensity records are correlated with SINT-800, revealing a good correspondence back to ca 250 ka. Below this level correlation becomes blurred. Depth-age plots show two linear segments (similar slopes) separated by a short break, suggesting a temporary change in sedimentation rate (hiatus?). The break corresponds with anomalous variations in the compositional S-0.3T-parameter. 1Jakobsson M., {\o}vlie R., An-Hanbali H., Arnold E., Backman J. and Mörth M., 2000. Manganese and color cycles in Arctic Ocean sediments constrain Pleistocene chronology. Geology, 28, 23-26.

Department

Center for Coastal and Ocean Mapping

Publication Date

12-2002

Volume

83, Issue 47

Journal Title

EOS Transactions, American Geophysical Union

Conference Date

Dec 6 - Dec 10, 2002

Publisher Place

San Francisco, CA, USA

Publisher

American Geophysical Union Publications

Document Type

Conference Proceeding

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