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Correlations between the Lomonosov Ridge, Marvin Spur and adjacent basins of the Arctic Ocean based on seismic data
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
2009 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 472, no 1-4, 309-322 p.Article in journal (Refereed) Published
Abstract [en]

Seismic profiles across the Lomonosov Ridge, Marvin Spur and adjacent basins, acquired near the North Pole by the drifting ice-station NP-28, provide a reflection image of the upper parts of the Ridge that is readily correlatable with those acquired by the Alfred Wegner Institute closer to the Siberian margin. A prominent flat-lying composite reflection package is seen in most parts of the Ridge at a few hundred meters below the sea bottom. Underlying reflections are variable in intensity and also in dip. The base of this reflection package is often accompanied by a sharp increase in P-velocity and defines a major angular discontinuity, referred to here as the Lomonosov Unconformity. The Arctic Coring Expedition (ACEX) cored the first c. 430 m section on the Lomonosov Ridge near the North Pole, in 2004 defining the deeper water character of the Neogene and the shallower water Paleogene sediments. These boreholes penetrated the composite reflection package towards the base of the hole and identified sediments (our Unit III) of late Paleocene and early Eocene age. Campanian beds at the very base of the hole were thought to be representative of the units below the Lomonosov Unconformity, but the P-velocity data suggest that this is unlikely. Correlation of the lithologies along the top of the Lomonosov Ridge and to the Marvin Spur indicates that the Marvin Spur is a sliver of continental crust closely related to, and rifted off the Ridge. This narrow (50 km wide) linear basement high can be followed into, beneath and across the Makarov Basin, supporting the interpretation that this Basin is partly resting on thinned continental crust. In the Makarov Basin, the Paleogene succession is much thicker than on the Ridge. Thus, the condensed, shallow water succession (with hiati) was deposited on the Ridge during rapid Eocene to Miocene subsidence of the Basin. In the Amundsen Basin, adjacent to the Lomonosov Ridge, the sedimentary successions thicken towards the Canadian margin and the reflections on the Ridge are not readily identifiable. The approximate ages of the sedimentary units are inferred from their relationships to the linear magnetic anomalies in the Basin. Lomonosov acoustic basement dips gently into the Basin over a distance of about 100 km and the linear negative anomaly, previously thought to be chron 25, is probably related to a rift-related mafic intrusive complex.

Place, publisher, year, edition, pages
2009. Vol. 472, no 1-4, 309-322 p.
Keyword [en]
Arctic Ocean, Lomonosov Ridge, Marvin Spur, Makarov Basin, Amundsen Basin, Reflection seismic
National Category
Geosciences, Multidisciplinary
URN: urn:nbn:se:uu:diva-121755DOI: 10.1016/j.tecto.2008.05.029ISI: 000268086800028OAI: oai:DiVA.org:uu-121755DiVA: diva2:306496
Available from: 2010-03-31 Created: 2010-03-29 Last updated: 2011-03-11Bibliographically approved
In thesis
1. Geophysical Studies Bearing on the Origin of the Arctic Basin
Open this publication in new window or tab >>Geophysical Studies Bearing on the Origin of the Arctic Basin
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Deep troughs and ridges of the Arctic Basin are some of the least known features of the Earth's crust. Some of the ridges, eg. Chukchi and Nordwind, are connected directly to the continental shelves and are certainly submarine promontories of the latter. The character of the Lomonosov Ridge as a narrow slice of continental crust that separated from the Eurasian margin in the early Cenozoic (by opening of the Eurasian Basin), is not in doubt. Recent drilling (ACEX) and piston coring have confirmed this interpretation. However there are many other ridges and some of the troughs that are of uncertain origin.

Seismic research in combination with potential field data over the East-Siberian margin, Podvodnikov and Makarov basins and the Mendeleev Ridge, presented here, provides a framework for understanding this enigmatic part of the Earth. The constrained models of the crust illustrate their structure. The crust beneath the East Siberian margin is up to 40 km thick; it thins to about 20 km towards to the Podvodnikov Basin. The models over the Arlis Gap, in the middle of the Podvodnikov Basin, and the Mendeleev Ridge have shown that the crust beneath both these features is anomalously thick (up to 28–32 km) and has a velocity structure that suggests the presence of highly attenuated continental crust. The crustal thickness over the Makarov Basin varies from 8 km to 15 km.

Reflection profiles provide evidence of the character and thickness of the sedimentary cover (mostly Cenozoic and late Mesozoic), both on the ridges and beneath the troughs. Presented here is evidence that some of the ridges (eg. Marvin Spur) appear to be fragments of continental crust rifted off the Lomonosov Ridge (with a similar, unconformable Cenozoic cover); however, they gently plunge into and beneath troughs (eg. Makarov Basin).

Reflection seismic data collected by the HOTRAX expedition in 2005 over the central part of the Lomonosov Ridge illustrate the sedimentary structure on the top of the Ridge and in an internal basin. The main sedimentary units can be interpreted by correlation with the ACEX results. The major fault separating the surrounding ridges from the internal basin appears to have a roll over anticline in the hanging wall, suggesting that the basin was created by a growth fault. The seismic lines provide evidence of gently folded basement beneath the Lomonosov Ridge with intra basement reflections are usually parallel to the upper surfaces; in combination with velocities (c. 4–5 km/s), these suggest the presence of old well-consolidated sediments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 79 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 729
refraction seismic, reflection seismic, crustal structure, Arctic Ocean, Amerasia Basin.
Research subject
Geophysics with specialization in Seismology
urn:nbn:se:uu:diva-121757 (URN)978-91-554-7771-4 (ISBN)
Public defence
2010-05-07, Axel Hambergsalen, Geocentrum, Villavagen 16, Uppsala, Uppsala, 10:00 (English)
Available from: 2010-04-07 Created: 2010-03-29 Last updated: 2010-04-07

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