Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
High Arctic submarine glaciogenic landscapes: their formation and significance
Stockholm University, Faculty of Science, Department of Geological Sciences.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on studies of glacial and slope morphology in the high Arctic of western Greenland shelf and the Molloy Hole seafloor spreading area, based on high-resolution acoustic methods and other geophysical data. The main purpose is to improve our understanding of glacial dynamics and associated processes in the marginal region of a large marine-terminating ice sheet. Newly acquired data, together with existing datasets have been compiled to create bathymetric models, which were used to study the seafloor landscape and its preserved record of glacial and sedimentary processes. The new bathymetric models were used with novel processing tools combined with seismic profiles, sub-bottom profiles and overlays of geological- and gravimetric maps to describe the observed landforms and interpret causal relationships. The main conclusions are:

1)   The underlying geology is an important control on the cross-shelf trough (CST) dimensions in western Greenland. This is likely due to the influence of underlying geology to the frictional resistance of the ice flow over the basement rock. Our observations show that ice streaming in areas with basaltic bed-types cause minimal over-deepening of the main trunk of the trough, which also has weaker lateral boundaries allowing the ice stream to shift flow direction more easily. CSTs on the Cenozoic-Mesozoic sedimentary basins indicate a stronger eroding and more focused paleo-ice streams.

2)   Bedrock lithology has an important part in controlling the location of the head-to-trough transition in CSTs of western Greenland. The areas where the head’s network of channels converges to form the main trunk of the trough are mostly located on the boundary from crystalline to sedimentary bedrock. These areas are also marked by distinct over-deepenings.

3)   Preglacial conditions such as faults/fractures and lithological properties of the basement rocks in western Greenland served as an important control on the erosional potential of the glacial processes, particularly on a local scale. Faults and fractures have led to the topographic steering of the ice flow that causes further excavation and erosion of the bed, while uneven erosion patterns, based on differences in glacial morphological features, is observed between areas of adjacent bedrocks with different lithology.

4)   The occurrence of trough mouth fans is suggested to be controlled mainly by the shelf width, which governs the glacial flow length along available sediment sources. It is also controlled by the continental slope steepness, which may be too steep for sediment fans to accumulate, or may cause slope failure which eventually transports the sediments to the deep basin.

5)   The maximum ice extent in west Greenland extended towards the shelf edge. Geomorphological evidence of ice margin standstills and slow retreat (grounding zone wedges and transverse moraines) in some areas reveal a multi-stage deglaciation process.

6)   The view of a highly dynamic paleo-Greenland ice sheet is supported by the presence of a large number of CSTs which hosted ice streams, and evidence of ice stream flow-switching throughout one or several glaciations.

7)   The influence of glacial sedimentary processes extends into the deepest areas of the Arctic Ocean. A submarine landslide, here termed the Molloy Slide, has been described in the Molloy Hole in the Davis Strait between Greenland and Svalbard. This slide was likely caused by massive glacial sediment deposition along the west Svalbard margin.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University , 2016. , 34 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 360
Keyword [en]
High Arctic, GrIS, marine geophysics, glaciogenic landscapes, ice streams, submarine slides
National Category
Geology
Research subject
Marine Geology
Identifiers
URN: urn:nbn:se:su:diva-127165ISBN: 978-91-7649-367-0 (print)OAI: oai:DiVA.org:su-127165DiVA: diva2:907168
Public defence
2016-04-20, William-Olssonsalen, 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 1: Manuscript. Paper 2: Manuscript.

Available from: 2016-03-28 Created: 2016-02-26 Last updated: 2017-02-17Bibliographically approved
List of papers
1. Glacial landforms in a hard bedrock terrain, Melville Bay off nortwestern Greenland
Open this publication in new window or tab >>Glacial landforms in a hard bedrock terrain, Melville Bay off nortwestern Greenland
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Geology
Research subject
Marine Geology
Identifiers
urn:nbn:se:su:diva-127164 (URN)
Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2016-03-10Bibliographically approved
2. Paleo-ice stream behavior inferred from cross-shelf troughs and submarine glaciogenic debris flows along the west Greenland continental margin
Open this publication in new window or tab >>Paleo-ice stream behavior inferred from cross-shelf troughs and submarine glaciogenic debris flows along the west Greenland continental margin
(English)Manuscript (preprint) (Other academic)
Keyword
GrIS, bathymetric compilation, west Greenland, cross shelf troughs, ice streams, shifting ice streams
National Category
Geology
Research subject
Marine Geology
Identifiers
urn:nbn:se:su:diva-127160 (URN)
Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2016-03-10Bibliographically approved
3. Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole
Open this publication in new window or tab >>Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole
2014 (English)In: Geo-Marine Letters, ISSN 0276-0460, E-ISSN 1432-1157, Vol. 34, no 4, 315-325 p.Article in journal (Refereed) Published
Abstract [en]

The western Svalbard continental margin contains thick sediment sequences with areas known to contain gas hydrates. Together with a dynamic tectonic environment, this makes the region prone to submarine slides. This paper presents results from geophysical mapping of the deepest part of the high Arctic environment, the Molloy Hole. The mapping includes multibeam bathymetry, acoustic backscatter and sub-bottom profiling. The geophysical data reveal seabed features indicative of sediment transport and larger-scale mass wasting. The large slide scar is here referred to as the Molloy Slide. It is located adjacent to the prominent Molloy Hole and Ridge system. The slide is estimated to have transported >65 km(3) of sediments over the deep axial valley of the Molloy Ridge, and further into the Molloy Hole. A unique feature of this slide is that, although its run-out distance is relatively short (<5 km), it extends over an enormous vertical depth (>2,000 m) as a result of its position in a complex bathymetric setting. The slide was most likely triggered by seismic activity caused by seafloor spreading processes along the adjacent Molloy Ridge. However, gas-hydrate destabilization may also have played a role in the ensuing slide event.

National Category
Earth and Related Environmental Sciences
Research subject
Marine Geology
Identifiers
urn:nbn:se:su:diva-108215 (URN)10.1007/s00367-014-0371-5 (DOI)000341828100002 ()
Note

AuthorCount:4;

Available from: 2014-10-15 Created: 2014-10-15 Last updated: 2017-12-05Bibliographically approved
4. High resolution mapping of offshore and onshore glaciogenic features in metamorphic bedrock terrain, Melville Bay, northwestern Greenland
Open this publication in new window or tab >>High resolution mapping of offshore and onshore glaciogenic features in metamorphic bedrock terrain, Melville Bay, northwestern Greenland
Show others...
2015 (English)In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 250, 29-40 p.Article in journal (Refereed) Published
Abstract [en]

Geomorphological studies of previously glaciated landscapes are important to understand how ice sheets and glaciers respond to rapidly changing climate. Melville Bay, in northwestern Greenland, contains some of the most sensitive but least studied ice sheet sectors in the northern hemisphere, where the bathymetric knowledge previously was restricted to a few sparsely distributed single beam echo soundings. We present here the results of high-resolution, geomorphological mapping of the offshore and onshore landscapes in Melville Bay using multibeam sonar and satellite data, at 5- and 10-m resolutions respectively. The results show a similar areally-scoured bedrock-dominated landscape with a glacially modified cnoc-and-lochan morphology on the inner shelf (150-500 m depth) and on the nearby exposed coast. This is manifested by the presence of U-shaped troughs, moutonee-type elongated landforms, stoss-and-lee forms, and streamlined features. The submarine landscape shows features that are characteristic of bedrock in folded, faulted, and weathered metamorphic terrain, and, to a lesser extent, glacially molded bedforms; while coastal landforms exhibit higher relief, irregular-shaped basins, and more subdued fracture valleys. Although generally similar, the onshore and offshore landscapes contain examples of distinctly different landform patterns, which are interpreted to reflect a longer exposure to long-term deep weathering as well as to more recent periglacial weathering processes on land. The spatial variability in the distribution of landforms across the landscape in both study areas is mostly attributed to differences in lithological properties of the bedrock. The lack of sediment cover on the inner shelf is likely a result of a capacity for sediment erosion and removal by the West Greenland Current flowing northward over the area in combination with limited sediment supply from long sea ice-cover seasons. The distribution and orientation of the landforms in the offshore part indicate ice movement toward the NW, and suggests that this area acted as a tributary or onset region for the major paleo ice stream that formed the present day Melville Bay Trough.

Keyword
Melville Bay, northwest Greenland, Glacial erosional landforms, High-resolution mapping, Combined onshore-offshore mapping
National Category
Earth and Related Environmental Sciences
Research subject
Marine Geology
Identifiers
urn:nbn:se:su:diva-124161 (URN)10.1016/j.geomorph.2015.08.011 (DOI)000364266800003 ()
Available from: 2015-12-22 Created: 2015-12-15 Last updated: 2017-12-01Bibliographically approved

Open Access in DiVA

High Arctic submarine glaciogenic landscapes(8860 kB)136 downloads
File information
File name FULLTEXT03.pdfFile size 8860 kBChecksum SHA-512
b8dd1a30e662b8e0202f9a3dfa3aa859e5fb8d0f1f8ad61f61e816b758375740c91bc6cea15d2cd9793a9a8769e96fe80c43e60cdc77e0bb845b8c11af261e8a
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Freire, Francis Fletcher
By organisation
Department of Geological Sciences
Geology

Search outside of DiVA

GoogleGoogle Scholar
Total: 136 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 353 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf