| Summary: | This dissertation comprises a series of studies that use sedimentary records combined with regional geophysics to explore and expand our understanding of the central Arctic Ocean throughout the Cenozoic. Recovered from the Lomonosov Ridge during the Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition; ACEX), the sediment cores provide the only long term marine geologic record from the central Arctic Ocean and offer the first means for integrating and reinterpreting over 30 years of predominantly geophysical data collection. Results from a stress history analysis reveal that there is no evidence for largescale erosional events in the sediments from the Lomonosov Ridge. This implies that the transition from the Paleogene to Neogene, represented by a 25 million year (Myr) hiatus in the ACEX record, is a period of low to non-deposition, indicating a dynamic environment in which no large sedimentary deposits accumulated. Although regional seismic evidence suggests the grounding of massive icebergs or ice sheets during the Pleistocene, the lack of overconsolidated sediments argues against grounding at the drilling sites on the Lomonosov Ridge. Longstanding controversy over Quaternary sedimentation rates in the central Arctic Ocean arises from the unusual paleomagnetic inclination records from these sediments. By integrating the ACEX record with existing sediment cores proximal to the drill sites, it is shown that although they can be broadly correlated, the position and duration of excursions are not constrained stratigraphically. Petrophysical and environmental magnetic records that track primary glacial and interglacial depositional signals are identified and provide a means for constructing a Quaternary chronostratigraphy for central Arctic Ocean sediments. Simple subsidence models that describe the continued sinking of the Lomonosov Ridge since the late Paleocene rifting from the Barents-Kara Sea margin do not adequately account for the paleoenvironmental indicators seen bounding the 25 Myr mid-Cenozoic hiatus in the ALEX record. Variations in heat flow along strike of the Lomonosov Ridge and regional seismic data both suggest a more complicated geodynamic Cenozoic evolution for the Ridge. A period of tectonically induced uplift of the Lomonosov Ridge is argued as a possible mechanism to account for these diverse observations.
|
|---|