3‐D Structure of the Variscan Thrust Front in Northern France: New Insights From Seismic Reflection Profiles. Issue 7 (14th July 2021)

• Record Type: Journal Article
• Authors: Laurent, A.; Averbuch, O.; Beccaletto, L.; Graveleau, F.; Lacquement, F.; Capar, L.; Marc, S.
• Is Part Of: Tectonics. Volume 40:Issue 7(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-14
• Subjects: seismic interpretation -- orogenic thrust front -- variscan geodynamics -- out‐of‐sequence thrusting -- frontal triangle zone -- tectonic inheritance; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2020TC006642
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: In NW Europe, the late Carboniferous Variscan collision between the Laurussia and the Armorica‐Gondwana continental blocks led to the development of a crustal‐scale north‐verging thrust system along the southern Laurussian margin. In northern France, the 3‐D geometry and kinematics of the Variscan deformation front have been investigated on the basis of reprocessing and interpreting 532 km of industry‐level seismic reflection profiles. This extensive seismic imaging provides new constraints on the structural and kinematic features of the orogenic front. It particularly emphasizes the localization of displacement along the main frontal thrust zone that accommodated more than 50 km of total displacement of the allochthonous units above the foreland. It also highlights the induced large underthrusting of the foreland basin below the frontal thrust zone, and its truncation in a general out‐of‐sequence mode of thrust propagation. We built structural maps that led to better delineating a major NW‐SE lateral ramp along the main frontal thrust. The Mid‐Upper Devonian series within the flexured foreland were deformed at depth by N060–080° trending and N110–130° trending syn‐sedimentary normal faults that led to their south‐to southwestward thickening. These pre‐existing structures along the margin have exerted a primary control on the ensuing dynamics and geometry of the Northern Variscan Front by localizing both the frontal and lateral ramps during thrust wedge growth. Key Points: Seismic data emphasize the large underthrusting of the Carboniferous foreland basin beneath the northern France Variscan thrust wedge 3‐D imaging of the main thrust Allochton Main Basal Thrust evidences a major lateral ramp segmenting the frontal thrust zone Inherited normal faults from the Laurussian margin exerted a major control on the dynamics and segmentation of the thrust front