Mechanics of thick-skinned Variscan overprinting of Cadomian basement (Iberian Variscides) |
| |
| Authors: | António Ribeiro José Munhá António Mateus Paulo Fonseca Eurico Pereira Fernando Noronha José Romão José Rodrigues Paulo Castro Carlos Meireles Narciso Ferreira |
| |
| Institution: | 1. Department Geologia and CEGUL, Faculdade de Ciências, Universidade de Lisboa, Ed. C6, Piso 3, Campo Grande, 1749-016 Lisboa, Portugal;2. Department de Geologia, Laboratório Nacional de Energia e Geologia, 4466-956 S. Mamede Infesta, Portugal;3. Department Geologia and CEGUP, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal;4. Department Geologia, Laboratório Nacional de Energia e Geologia, Apartado 7586, 2721-866 Alfragide, Portugal |
| |
| Abstract: | Remnants of the Cadomian basement can be found in the Iberian Variscides (IBVA) in several key sectors of its autochthonous units (composed of Neoproterozoic to Lower Palaeozoic metasedimentary sequences) and within the Continental Allochthonous Terrane (CAT). Comprehensive characterization of these critical exposures shows that the prevailing features are related to major geological events dated within the age range of 620–540 Ma. Indeed, near the Cambrian–Ordovician boundary, the IBVA Internal Zones experienced pervasive basement thinning and cover thickening, reflecting diffusive displacement of intracratonic rifting that continued until Lower Devonian times. In the thick-skinned Internal Zones, Helvetic/Penninic style nappes were generated, whereas flower upright axial structures developed along transpressive, intraplate shear zones. These features contrast with those preserved in the thin-skinned IBVA External Zones, dominated by décollements above (un-)deformed Palaeozoic and Cadomian basement. The inferred attenuation of rheological contrast between Cadomian basement and Palaeozoic cover can be explained by inherited fabrics due to thermal softening operated during the Cambrian–Lower Devonian extensional regime. Deeper décollements (and subsequent strain partitioning) are also expected to develop at the upper-lower crust (and at the Moho?) transition, as imaged by the available seismic profiling and MT surveys. The whole data implies a significant discontinuity between Cadomian and Variscan Cycles that should have constrained subsequent lithospheric evolution. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
