uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • 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
3D reflection seismic imaging at the 2.5 km deep COSC-1 scientific borehole, central Scandinavian Caledonides
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. (Applied Geophysics)ORCID iD: 0000-0003-1963-2588
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.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Show others and affiliations
2016 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 689, 40-55 p.Article in journal (Refereed) Published
Abstract [en]

The 2.5 km deep scientific COSC-1 borehole (ICDP 5054-1-A) was successfully drilled with nearly complete core recovery during spring and summer of 2014. Downhole and on-core measurements through the targeted Lower Seve Nappe provide a comprehensive data set. An observed gradual increase in strain below 1700 m, with mica schists and intermittent mylonites increasing in frequency and thickness, is here interpreted as the basal thrust zone of the Lower Seve Nappe. This high strain zone was not fully penetrated at the total drilled depth and is thus greater than 800 m in thickness.

To allow extrapolation of the results from downhole logging, core analysis and other experiments into the surrounding rock and to link these with the regional tectonic setting and evolution, three post-drilling high-resolution seismic experiments were conducted in and around the borehole. One of these, the first 3D seismic reflection land survey to target the nappe structures of the Scandinavian Caledonides, is presented here. It provides new information on the 3D geometry of structures both within the drilled Lower Seve Nappe and underlying rocks down to at least 9 km.

The observed reflectivity correlates well with results from the core analysis and downhole logging, despite challenges in processing. Reflections from the uppermost part of the Lower Seve Nappe have limited lateral extent and varying dips, possibly related to mafic lenses or boudins of variable character within felsic rock. Reflections occurring within the high strain zone, however, are laterally continuous over distances of a kilometer or more and dip 10–15° towards the southeast. Reflections from structures beneath the high strain unit and the COSC-1 borehole can be followed through most of the seismic volume down to at least 9 km and have dips of varying degree, mainly in the east–west thrust direction of the orogen.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 689, 40-55 p.
Keyword [en]
3D reflection seismic, continental scientific deep drilling, borehole geophysics, collisional orogeny in the Scandinavian Caledonides, Seve Nappe Complex, shear zones
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
URN: urn:nbn:se:uu:diva-261087DOI: 10.1016/j.tecto.2015.12.013ISI: 000387522100005OAI: oai:DiVA.org:uu-261087DiVA: diva2:849642
Projects
Collisional Orogeny in the Scandinavian Caledonides (COSC)
Funder
Swedish Research Council, 2013-5780Swedish Research Council, 2013-94German Research Foundation (DFG), BU1364/10-1German Research Foundation (DFG), GI982/2-1
Available from: 2015-08-29 Created: 2015-08-29 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Geophysical studies of the upper crust of the central Swedish Caledonides in relation to the COSC scientific drilling project
Open this publication in new window or tab >>Geophysical studies of the upper crust of the central Swedish Caledonides in relation to the COSC scientific drilling project
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Collisional Orogeny in the Scandinavian Caledonides (COSC) project aims to provide a deeper understanding of mountain belt dynamics through scientific deep drilling in the central parts of the mountain belt of western Sweden. The main targets include a subduction related allochthon, the basal orogenic detachment and the underlying partially subducted Precambrian basement. Research covered by this thesis, focusing primarily on reflection seismic data, was done within the framework of the COSC project.

The 55 km long composite COSC Seismic Profile (CSP) images the upper crust in high resolution and established the basis for the selection of the optimum location for the two 2.5 km deep COSC boreholes. Together with potential field and magnetotelluric data, these profiles allowed the construction of a constrained regional interpretation of the major tectonic units. Non-conventional pseudo 3D processing techniques were applied to the 2D data prior to the drilling of the first borehole, COSC-1, to provide predictions about the 3D geometry of subsurface structures and potential zones of interest for the sampling programs.

COSC-1 was drilled in 2014 and reached the targeted depth with nearly complete core recovery. A continuous geological section and a wealth of information from on-site and off-site scientific investigations were obtained. A major post-drilling seismic survey was conducted in and around the borehole and included a 3D reflection seismic experiment. The structurally and lithologically complex Lower Seve Nappe proved difficult to image in detail using standard processing techniques, but its basal mylonite zone and underlying structures are well resolved. The 3D data, from the surface down to the total drilled depth, show good correlation with the initial mapping of the COSC-1 core as well as with preliminary results from on-core and downhole logging.  

Good correlation is also observed between the 2D and 3D reflection seismic datasets. These will provide a strong link between the two boreholes and a means to extrapolate the results from the cores and boreholes into the surrounding rock. Ultimately, they will contribute to the deeper understanding of the tectonic evolution of the region, the Scandinavian Caledonides and the formation of major orogens. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1281
Keyword
reflection seismic, collisional orogeny, Scandinavian Caledonides, COSC, scientific drilling, geophysical logging, gravity, magnetics
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-261112 (URN)978-91-554-9320-2 (ISBN)
Public defence
2015-10-16, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Projects
Collisional Orogeny in the Scandinavian Caledonides
Funder
Swedish Research Council, 2009-4413Swedish Research Council, 2013-5780
Available from: 2015-09-25 Created: 2015-08-30 Last updated: 2016-08-16Bibliographically approved

Open Access in DiVA

fulltext(6165 kB)95 downloads
File information
File name FULLTEXT01.pdfFile size 6165 kBChecksum SHA-512
bf6770ca06758198cdf871f818ef1e76eede40b7d56afc348f9b96f20c3c6063ab678ebf368eccda6b3cf8fef3d34e34666bb57a8cb3736bab38009c8587dda0
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Authority records BETA

Hedin, PeterAlmqvist, BjarneBerthet, ThéoJuhlin, Christopher

Search in DiVA

By author/editor
Hedin, PeterAlmqvist, BjarneBerthet, ThéoJuhlin, Christopher
By organisation
Geophysics
In the same journal
Tectonophysics
Geophysics

Search outside of DiVA

GoogleGoogle Scholar
Total: 95 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

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 643 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • 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