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The Thor suture zone: From subduction to intraplate basin setting


Author: Smit, J. · Wees, J.D. van · Cloetingh, S.
Publisher: Geological Society of America
Source:Geology, 9, 44, 707-710
Identifier: 572624
doi: doi:10.1130/G37958.1
Keywords: Geosciences · Metamorphic rocks · Seismology · Wave propagation · Accretionary complex · Back-arc extensions · Cascadia subduction zone · Gas reservoir · Inversion structures · P-wave velocity · Seismic profiles · Geological Survey Netherlands · 2015 Energy · Geo · PG - Petroleum Geosciences SGE - Sustainable Geo Energy · ELSS - Earth, Life and Social Sciences


The crustal seismic velocity structure of northwestern Europe shows a low P-wave velocity zone (LVZ) in the lower crust along the Caledonian Thor suture zone (TSZ) that cannot be easily attributed to Avalonia or Baltica plates abutting the TSZ. The LVZ appears to correspond to a hitherto unrecognized crustal segment (accretionary complex) that separates Avalonia from Baltica, explaining well the absence of Avalonia further east. Consequently, the northern boundary of Avalonia is shifted ~150 km southward. Our interpretation, based on analysis of deep seismic profiles, places the LVZ in a consistent crustal domain interpretation. A comparison with present-day examples of the Kuril and Cascadia subduction zones suggests that the LVZ separating Avalonia from Baltica is composed of remnants of the Caledonian accretionary complex. If so, the present-day geometry probably originates from pre-Variscan extension and eduction during Devonian-Carboniferous backarc extension. The reinterpretation of deep crustal zonation provides a crustal framework in which the northern limit of Avalonia corresponds to the southern limit of the deep North German Basin and the northern limit of prolific gas reservoirs and late Mesozoic inversion structures. © 2016 Geological Society of America.