Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen

Z. Hajnal, S. Lucas, D. White, J. Lewry, S. Bezdan, M. R. Stauffer, M. D. Thomas

Research output: Contribution to journalArticle

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Abstract

Postcollisional (1.8-1.7 Ga) intracontinental deformation in the Trans-Hudson Orogen (Canada) produced a series of orogen-parallel high-angle faults and folds. In seismic eflection profiles, the faults are imaged by subvertical zones of diffractions and truncated reflections that extend to 4-8 s (12-24 km). The folded and faulted upper part of the crust is underlain by laterally coherent shallow-dipping reflections that are locally bounded by discrete, highly reflective zones. These zones are interpreted as detachments (shear zones) and can be traced from the upper to lower crust, where some of them appear to pass into laterally continuous reflections that define the Moho. Two distinct regimes of postcollisional crustal deformation are inferred from the seismic images: high-angle faulting and lateral block extrusion in the upper crust and low-angle ductile shearing in the mid/lower crust. The surface geology indicates that the faults resulted in southwest (orogen-parallel) extrusion of the orogen's internal zone relative to the bounding Archean Hearne and Superior cratons. Faulting was concurrent with the development of upright folds with trends that are subparallel to the extrusion direction. The seismic images suggest that the high-angle fold/fault structures are kinematically linked to low-angle detachments represented by laterally coherent, highly reflective zones. The detachment shear zones are inferred to have a top-to-the-southwest sense of shear associated with a subhorizontal, northeast-southwest extension direction, parallel to those observed for 1.83-1.80 Ga collisional shear zones exposed in major postcollisional fold culminations. Long-lived orogen-parallel extension is interpreted as a consequence of the boundary conditions imposed by the northeast trend of both the Superior and Hearne margins.

Original languageEnglish
Pages (from-to)427-439
Number of pages13
JournalTectonics
Volume15
Issue number2
Publication statusPublished - Apr 1996

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detachment
seismic reflection
Extrusion
Faulting
crusts
extrusion
shear
fold
shear zone
lower crust
Geology
Shearing
faulting
trends
Diffraction
Boundary conditions
cratons
crustal deformation
geology
Moho

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Hajnal, Z., Lucas, S., White, D., Lewry, J., Bezdan, S., Stauffer, M. R., & Thomas, M. D. (1996). Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen. Tectonics, 15(2), 427-439.

Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen. / Hajnal, Z.; Lucas, S.; White, D.; Lewry, J.; Bezdan, S.; Stauffer, M. R.; Thomas, M. D.

In: Tectonics, Vol. 15, No. 2, 04.1996, p. 427-439.

Research output: Contribution to journalArticle

Hajnal, Z, Lucas, S, White, D, Lewry, J, Bezdan, S, Stauffer, MR & Thomas, MD 1996, 'Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen', Tectonics, vol. 15, no. 2, pp. 427-439.
Hajnal Z, Lucas S, White D, Lewry J, Bezdan S, Stauffer MR et al. Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen. Tectonics. 1996 Apr;15(2):427-439.
Hajnal, Z. ; Lucas, S. ; White, D. ; Lewry, J. ; Bezdan, S. ; Stauffer, M. R. ; Thomas, M. D. / Seismic reflection images of high-angle faults and linked detachments in the Trans-Hudson Orogen. In: Tectonics. 1996 ; Vol. 15, No. 2. pp. 427-439.
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