Pleistocene stratigraphy and paleoenvironmental variation from Lomonosov Ridge sediments, central Arctic Ocean

High resolution seismoacoustic chirp sonar data and piston cores were collected from the Lomonosov Ridge in the central Arctic Ocean (85degrees-90degreesN; 130degrees-155degreesE). The chirp sonar data indicate substantial erosion on the ridge crest above 1000 mbsl while data from deeper sites show apparently undisturbed sedimentation. Piston cores from both the eroded ridge crest and the slopes have been analyzed for a variety of properties, permitting inter-core correlation and description of paleoenvironmental change over time. Based on the evidence of extensive sediment erosion at depths above 1000 mbsl, we infer that the top of the Lomonosov Ridge has been eroded by grounded ice during a prominent glacial event that took place during MIS 6 according to a newly published age model. This event is coeval with a dramatic shift from low amplitude glacial-interglacial variability to high amplitude variability recorded in the sedimentary record. The new age model used in our study is based on nannofossil biostratigraphy and correlation between sedimentary cycles and a low-latitude oxygen isotope record and confirmed by paleomagnetic polarity studies where negative paleomagnetic inclinations are assigned to excursions. Due to the controversy between this age model and age models that assign the negative paleomagnetic inclinations to polarity reversals, we provide a correlation to Lomonosov Ridge core PS2185-6 [Spielhagen et al., Geology, 25 (1997) 783). According to the latter age models, the Lomonosov Ridge was eroded by ice grounding much earlier, at MIS 16. (C) 2001 Elsevier Science B.V. All rights reserved.