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Quaternary paleoceanography of the Arctic Ocean: A study of sediment stratigraphy and physical properties
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A Quaternary perspective on the paleoceanographic evolution of the central Arctic Ocean has been obtained in this PhD thesis by studying sediment cores from all of the Arctic’s major submarine ridges and plateaus. The included cores were mainly recovered during the Healy-Oden Trans-Arctic expedition in 2005 and the Lomonosov Ridge off Greenland expedition in 2007. One of the main thesis objectives is to establish whether different sediment depositional regimes prevailed in different parts of the central Arctic Ocean during the Quaternary and, if so, establish general sedimentation rates for these regimes. This was approached by dating key cores using the decay of the cosmogenic isotopes 10Be and 14C, and through stratigraphic core-to-core correlation using sediment physical properties. However, the Arctic Ocean sea ice complicated the use of 10Be for dating because a solid sea ice cover prevents the 10Be isotopes from reaching the seafloor, resulting in too old ages. Dating using 14C is also complicated due to uncertain marine reservoir age corrections in the central Arctic Ocean. The core-to-core correlations show five areas with different depositional regimes; the northern Mendeleev Ridge and Alpha Ridge, southern Mendeleev Ridge, Morris Jesup Rise, Lomonosov Ridge and Yermak Plateau, listed in the order of increasing sedimentation rates from ~0.5cm/ka to ~4.8 cm/ka. A detailed study of the relationship between sediment bulk density and grain sizes suggests a strong link between variations in clay abundance and bulk density. Grain size analysis of a Lomonosov Ridge core show that fine silt and clay dominates the interglacials, possibly due to increased suspension freezing of these size fractions into sea ice and/or nepheloid transport. Sediments younger than the marine isotope stage (MIS) 7 generally contain more coarse silt, attributed to a regime shift during the Quaternary with increased iceberg transport into the central Arctic Ocean from MIS 6 and onwards.

Place, publisher, year, edition, pages
Stockholm: Department of Geology and Geochemistry, Stockholm University , 2009. , 37 p.
Series
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 337
Keyword [en]
Arctic Ocean, sedimentology, Quaternary, stratigraphy, physical properties
National Category
Earth and Related Environmental Sciences Geology Geology
Research subject
Marine Geoscience
Identifiers
URN: urn:nbn:se:su:diva-30895ISBN: 978-91-7155-968-5 (print)OAI: oai:DiVA.org:su-30895DiVA: diva2:274706
Public defence
2009-11-27, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: In progress. Paper 4: In progress. Paper 5: In progress. Paper 6: In progress. Available from: 2009-11-05 Created: 2009-10-30 Last updated: 2009-10-30Bibliographically approved
List of papers
1. Sedimentary regimes in Arctic’s Amerasian and Eurasian basins: Clues to differences in sedimentation rates
Open this publication in new window or tab >>Sedimentary regimes in Arctic’s Amerasian and Eurasian basins: Clues to differences in sedimentation rates
2008 (Swedish)In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 61, no 3-4, 275-284 p.Article in journal (Refereed) Published
Abstract [sv]

A standard lithostratigraphic model based on cores retrieved 1963–1973 from the ice island T-3 was developed by Clark et al. (1980) for the Amerasian Basin of the Arctic Ocean. We have investigated whether or not it is possible to apply this lithostratigraphy to cores from the Lomonosov Ridge, which can be correlated to Eurasian Basin cores, for the purpose of correlating the Amerasian and Eurasian stratigraphies. Published averaged

sedimentary proxies from a selected set of T-3 cores are used to correlate with the identical published proxies for the included Lomonosov Ridge cores. The standard lithostratigraphic classification could not be applied to the Lomonosov Ridge cores,

which is interpreted to result from differences in sedimentary regimes in the Amerasian and Eurasian Basins. These differences also apply to the barrier between the two basins, the Lomonosov Ridge. The general sedimentation rates are three to four times lower in the Amerasian Basin than in the Eurasian Basin if the first down-core paleomagnetic inclination change is used to correlate between the two basins whereas correlation based on sediment coarse fraction suggests only two times lower rates in the Amerasian Basin.

Keyword
Arctic Ocean, stratigraphy, sedimentary regimes, stratigraphic correlation, sedimentation rates
National Category
Geology
Identifiers
urn:nbn:se:su:diva-19508 (URN)10.1016/j.gloplacha.2007.10.007 (DOI)000255825900011 ()
Available from: 2008-11-15 Created: 2008-11-15 Last updated: 2017-12-13Bibliographically approved
2. Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores
Open this publication in new window or tab >>Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores
2009 (English)In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 68, no 1-2, 38-47 p.Article in journal (Refereed) Published
Abstract [en]

Neogene marine sediments can be dated via decay of the cosmogenic radionuclide 10Be. Two cores from theAlpha and Mendeleev Ridges in the Arctic Ocean have been analyzed for seawater-derived beryllium (Be)isotopes in order to date the sediments and to calculate sedimentation rates. The decrease of 10Be concentrationin the cores was used to calculate first order sedimentation rates. To eliminate the dilution effect of berylliumcaused by short-term changes in sedimentation rate and grain size, the 10Be concentrationswere normalized tothe terrigenous stable isotope 9Be determined in the same sample aliquot. The measured 10Be concentrationsyield low average sedimentation rates for the Alpha and Mendeleev Ridges of 2.3 mm ka−1 and 2.7 mm ka−1,respectively. Sedimentation rates calculated from the 10Be/9Be ratios result in similarly low values, rangingfrom 0.2 to 6.8 mm ka−1 for the Alpha Ridge core and from 1.9 to 6.9 mm ka−1 for the Mendeleev Ridge core.However, amino acid racemization dating for the past 150 ka of a core adjacent to the Mendeleev Ridge corestudied here indicates significantly higher sedimentation rates than calculated from the downcore decreaseof 10Be and 10Be/9Be. If such higher rates also prevailed at the locations of our cores, for which there isbiostratigraphic evidence, either the supply of 10Be was much lower than assumed or that of 9Be was muchhigher. This could imply that the signature of the deepwaters in this part of the Arctic Ocean compared to todaywas largely different for most of the past approximately one million years with a significantly lower 10Be/9Beratio. Our study also addresses the variability of beryllium isotopes in sediment cores across the Arctic Oceanthrough a comparison of previously published results. Calculated 10Be fluxes reveal low values in the AmerasianBasin and highest values in the Eurasian Basin, near the Fram Strait. The decrease of Be isotopes in the twostudied Amerasian Basin cores may thus have been caused by environmental factors such as significantlyreduced inflow of Atlantic waters in the past, reduced input of 10Be and/or increased input of 9Be from theshelves, combined with a more efficient sea ice shielding in this part of the Arctic Ocean.

National Category
Geology
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-30890 (URN)10.1016/j.gloplacha.2009.03.024 (DOI)000269401100005 ()
Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2017-12-12Bibliographically approved
3. Quaternary Arctic Ocean sea ice variations and deep water isolation times
Open this publication in new window or tab >>Quaternary Arctic Ocean sea ice variations and deep water isolation times
Show others...
2010 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, 3430-3441 p.Article in journal (Refereed) Published
Abstract [en]

A short sediment core retrieved from a local depression forming an intra basin on the Lomonosov Ridge during the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX) contains a record of the Marine Isotope Stages (MIS) 1-3 showing exceptionally high abundances of calcareous microfossils during parts of MIS 3. Based on radiocarbon dating, linear sedimentation rates of 7-9 cm/ka persist during the last deglaciation. Last Glacial Maximum (LGM) is partly characterized by a hiatus. Planktic foraminiferal abundance variations of Neogloboquadrina pachyderma sinistral and calcareous nannofossils reflect changes in Arctic Ocean summer sea ice coverage and probably inflow of subpolar North Atlantic water. Marine reservoir ages of 1400 years or more, at least during the last deglaciation, seem plausible from calibration of the radiocarbon ages using modeled reservoir corrections from previous studies in combination with the microfossil abundance record of the studied core. Paired benthic-planktic radiocarbon dated foraminiferal samples indicate a slow decrease in age difference between surface and bottom waters from the Late Glacial to the Holocene, suggesting circulation and ventilation changes.

National Category
Earth and Related Environmental Sciences
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-30891 (URN)10.1016/j.quascirev.2010.06.011 (DOI)000284724400007 ()
Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2017-12-12Bibliographically approved
4. Predictive relationships betweenbulk density and grain size in Pleistocene sediments from the Lomonosov Ridge
Open this publication in new window or tab >>Predictive relationships betweenbulk density and grain size in Pleistocene sediments from the Lomonosov Ridge
(English)Manuscript (preprint) (Other academic)
National Category
Geology
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-30893 (URN)
Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2010-01-14Bibliographically approved
5. Grain size distributions and ice-rafting in thecentral Arctic Ocean – a million year perspective
Open this publication in new window or tab >>Grain size distributions and ice-rafting in thecentral Arctic Ocean – a million year perspective
(English)Manuscript (preprint) (Other academic)
National Category
Geology
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-30892 (URN)
Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2010-01-14Bibliographically approved
6. Spatial and temporal ArcticOcean depositional regimes: a key to the evolution of ice and current patterns
Open this publication in new window or tab >>Spatial and temporal ArcticOcean depositional regimes: a key to the evolution of ice and current patterns
2010 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, 3644-3664 p.Article in journal (Refereed) Published
Abstract [en]

Sediment physical properties measured in cores from all the major ridges and plateaus in the central Arctic Ocean were studied in order to analyze the spatial and temporal consistency of sediment depositional regimes during the Quaternary. In total, six physiographically distinct areas are outlined. In five of these, cores can be correlated over large distances through characteristic patterns in sediment physical properties. These areas are (1) the southern Mendeleev Ridge, (2) the northern Mendeleev Ridge and Alpha Ridge, (3) the Lomonosov Ridge, (4) the Morris Jesup Rise and (5) the Yermak Plateau. Averaged downhole patterns in magnetic susceptibility, bulk density and lithostratigraphy were compiled to establish a composite stratigraphy for each area. In the sixth physiographic area, the Chukchi Borderland, repeated ice-grounding during recent glacial periods complicates the stratigraphy and prevents the compilation of a composite stratigraphy using the studied material. By utilizing published age models for the studied cores we are able to show that the northern Mendeleev Ridge and Alpha Ridge have the lowest average late Quaternary sedimentation rates, while intermediate sedimentation rates prevail on the southern Mendeleev Ridge and the Morris Jesup Rise. The second highest sedimentation rate is observed on the Lomonosov Ridge, whereas the average sedimentation rate on the Yermak Plateau is more than twice as high. The close correlation of physical properties within each area suggests uniform variations in sediment transport through time, at least throughout the later part of the Quaternary. The unique stratigraphic characteristics within each area is the product of similar past depositional regimes and are key for furthering our understanding of the evolution of ice drift and current patterns in the central Arctic Ocean.

National Category
Geology
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-30894 (URN)10.1016/j.quascirev.2010.06.005 (DOI)000284724400022 ()
Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2017-12-12Bibliographically approved

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