Publication Date:
2020-12-14
Description:
Thrusting at shallow depths often precludes analysis by means of structural indicators effective in other geological contexts (e.g., mylonites, sheath folds, shear bands). In this paper, a combination of techniques (includ- ing structural analysis, magnetic methods, as anisotropy of magnetic susceptibility and paleomagnetism, and paleo- thermometry) is used to define thrusting conditions, defor- mation, and transport directions in the Cameros–Demanda thrust (North Spain). Three outcrops were analyzed along this intraplate, large-scale major structure having 150 km of outcropping length, 30 km of maximum horizontal dis- placement, and 5 km of vertical throw. Results obtained by means of the different techniques are compared with data derived from cross sections and stratigraphic analy- sis. Mixed-layer illite–smectite and vitrinite reflectance indicating deep diagenetic conditions and mature stage of hydrocarbon generation suggests shallow depths during deformation, thus confirming that the protolith for most of the fault rocks is the footwall of the main thrust. Kinematic indicators (foliation, S/C structures, and slickenside stria- tions) indicate altogether a dominant NNW movement of the hanging wall in the western zone and NE in the eastern zone of the thrust, thus implying strain partitioning between different branches of the main thrust. The study of AMS in fault rocks (nearly 400 samples of fault gouge, breccia, and microbreccia) indicates that the strike of magnetic foliation is oblique to the transport direction and that the magnetic lineation parallelizes the projection of the transport direc- tion onto the kmax/kint plane in sites with strong shear defor- mation. Paleomagnetism applied to fault rocks indicates the existence of remagnetizations linked to thrusting, in spite of the shallow depth for deformation, and a strong defor- mation or scattering of the magnetic remanence vectors in the fault zone. The application of the described techniques and consistency of results indicate that the proposed multi- disciplinary approach is useful when dealing with thrusts at shallow crustal levels.
Description:
Published
Description:
1023–1055
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
JCR Journal
Keywords:
Intraplate thrusting
;
Fault rock
;
Cameros–Demanda thrust
;
Transport direction
;
Magnetic techniques
;
Paleothermometry
;
Solid Earth
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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