An insight into the sedimentary history of the Lomonosov Ridge, Arctic Ocean

isabel.sauermilch [ at ]


The Arctic Ocean region is of great interest in a number of fields. It plays, and has played in the geological past, a key role for the Earth’s climate and oceanic circulation and their evolution. Furthermore, the coastal states surrounding it are interested in staking territorial claims in the Central Arctic Ocean, because it is regarded to house potential resources that will become more accessible with the forecasted ongoing decrease of annual sea ice coverage. Despite this, previous investigations and knowledge are not numerous due to the predominant heavy ice conditions which make it difficult to reach this remote and harsh region. Open questions about fundamental issues exist, e.g. related to the complex tectonic evolution of the Arctic Basins, the glacial history, and the details of known paleoceanographic changes in the Cenozoic. During RV Polarstern Expedition ARK XXVIII/4 in summer 2014, sea ice conditions were optimal for the collection of a comprehensive network of multichannel seismic reflection data along the Lomonosov Ridge between 80°N and 85°N. Two aims of collecting these data, among others, were to provide an appropriate database for an IODP drilling proposal, and to enhance knowledge of sedimentary and tectonic processes in the area. In this thesis, the northern part of the collected seismic dataset is processed and interpreted. Depending on the sea ice conditions and required resolution of the data, four survey set-ups with different streamer settings (300 m, 600 m, 3000 m) and airgun clusters (3, 4 G-Guns, 2 GI-Guns) were used. The dataset consists of two seismic profiles across the Lomonosov Ridge and its adjacent basins, a detailed network of profiles around the proposed drilling site, LORI-5B, and an along-ridge profile acquired with the 3000 m streamer. The seismic data were processed with an emphasis on velocity analysis of the upper seismic portions and the suppression of multiple reflections. One of the main achievements of this thesis is a detailed velocity model for the sedimentary stratigraphy at the ridge crest that provides, among others, details for the proposed drilling site LORI-5B. Furthermore, the sedimentary layers overlying the ridge are subdivided into four prominent sequences; three upper sediment layers and an underlying unit of presumed metasedimentary composition. An approximate age model, as well as a projection of the part of the ridge between 83°N and 84°30’N to its conjugate, the Severnaya Zemlya Archipelago at the Eurasia margin, is realized. Additionally, mass wasting structures detected in seismic, Parasound and bathymetric data are described in relation to their morphology and sediment stability, and interpreted in terms of approximate timing and possible trigger mechanisms.

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Thesis (Master)
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Sauermilch, I. (2015): An insight into the sedimentary history of the Lomonosov Ridge, Arctic Ocean , Master thesis, University of Bremen, Bremen.

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