The role of bedding in the formation of fault–fold structures,
Autor(a) principal: | |
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Data de Publicação: | 2010 |
Outros Autores: | , |
Tipo de documento: | Artigo |
Idioma: | por |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10174/2983 |
Resumo: | Fold-fault structures within a major transpressional shear zone of the SW Iberian Massif were investigated by combining geological mapping, cross-section analysis and microtectonic studies. A significant example of contractional deformation is displayed in the Portalegre-Esperanc¸a Shear Zone (PESZ) where a heterogeneous Ordovician stratigraphic sequence, showing a strong competence contrast between quartzites, slates and quartzo-feldspathic rocks favoured strain localization and fault nucleation that controlled fold formation. The presence of pelitic layers within the thick-bedded quartzites had probably provided weakness zones that were more favourable for the strain localization than the previous foliation present in the quartzites. The quartzites and the quartzo-feldspathic rocks (granites and volcaniclastic rocks) accommodated heterogeneous high strain developing different degrees of mylonitization. The quartzites with protomylonitic textures are dominant and represent coarse-grained siliciclastic sediments that suffered metamorphism and partial dynamic recrystallization. Ultramylonites occur within discrete high-strain shear zones. It is probable that the strain localization in the PESZ involved both the effect of having layers of different competence and layers or stratigraphic contacts with rocks that experienced grain size reduction dominated by cataclasis and dislocation creep. Folds within quartzites with sub-horizontal to gently plunging hinges vary from closed to open in thick-bedded quartzites and from tight to closed in thin-bedded quartzites. Observed changes in structural style of deformed quartzites, slates and quartzo-feldspathic rocks are interpreted to result from the constraints imposed by the mechanical properties of the different lithologies. As the folds tightened during shortening, the alternating zones of contrasting competence favoured the disruption of the bedding. The deformation history in the PESZ was dominated by thrusting and strike-slip faulting along incompetent layers that locally developed staircase geometry and transected the lower Ordovician stratigraphic sequence. The kinematic model proposed for the PESZ is consistent with the models of transpressional shear zones stretched along strike with the development of coeval strike-slip and low angle oblique-slip faults associated to active buckle folds with axes parallel to the principal extension direction |
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The role of bedding in the formation of fault–fold structures,competence contrastmylonitizationfault nucleation and propagationfolds formationtranspressionFold-fault structures within a major transpressional shear zone of the SW Iberian Massif were investigated by combining geological mapping, cross-section analysis and microtectonic studies. A significant example of contractional deformation is displayed in the Portalegre-Esperanc¸a Shear Zone (PESZ) where a heterogeneous Ordovician stratigraphic sequence, showing a strong competence contrast between quartzites, slates and quartzo-feldspathic rocks favoured strain localization and fault nucleation that controlled fold formation. The presence of pelitic layers within the thick-bedded quartzites had probably provided weakness zones that were more favourable for the strain localization than the previous foliation present in the quartzites. The quartzites and the quartzo-feldspathic rocks (granites and volcaniclastic rocks) accommodated heterogeneous high strain developing different degrees of mylonitization. The quartzites with protomylonitic textures are dominant and represent coarse-grained siliciclastic sediments that suffered metamorphism and partial dynamic recrystallization. Ultramylonites occur within discrete high-strain shear zones. It is probable that the strain localization in the PESZ involved both the effect of having layers of different competence and layers or stratigraphic contacts with rocks that experienced grain size reduction dominated by cataclasis and dislocation creep. Folds within quartzites with sub-horizontal to gently plunging hinges vary from closed to open in thick-bedded quartzites and from tight to closed in thin-bedded quartzites. Observed changes in structural style of deformed quartzites, slates and quartzo-feldspathic rocks are interpreted to result from the constraints imposed by the mechanical properties of the different lithologies. As the folds tightened during shortening, the alternating zones of contrasting competence favoured the disruption of the bedding. The deformation history in the PESZ was dominated by thrusting and strike-slip faulting along incompetent layers that locally developed staircase geometry and transected the lower Ordovician stratigraphic sequence. The kinematic model proposed for the PESZ is consistent with the models of transpressional shear zones stretched along strike with the development of coeval strike-slip and low angle oblique-slip faults associated to active buckle folds with axes parallel to the principal extension direction2011-12-22T17:50:39Z2011-12-222010-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10174/2983http://hdl.handle.net/10174/2983por521-53545Geological Journalmpereira@uevora.ptndnd250Pereira, M. FranciscoSilva, Jose B.Ribeiro, Carlosinfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-01-03T18:39:43Zoai:dspace.uevora.pt:10174/2983Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T00:58:30.051256Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
The role of bedding in the formation of fault–fold structures, |
title |
The role of bedding in the formation of fault–fold structures, |
spellingShingle |
The role of bedding in the formation of fault–fold structures, Pereira, M. Francisco competence contrast mylonitization fault nucleation and propagation folds formation transpression |
title_short |
The role of bedding in the formation of fault–fold structures, |
title_full |
The role of bedding in the formation of fault–fold structures, |
title_fullStr |
The role of bedding in the formation of fault–fold structures, |
title_full_unstemmed |
The role of bedding in the formation of fault–fold structures, |
title_sort |
The role of bedding in the formation of fault–fold structures, |
author |
Pereira, M. Francisco |
author_facet |
Pereira, M. Francisco Silva, Jose B. Ribeiro, Carlos |
author_role |
author |
author2 |
Silva, Jose B. Ribeiro, Carlos |
author2_role |
author author |
dc.contributor.author.fl_str_mv |
Pereira, M. Francisco Silva, Jose B. Ribeiro, Carlos |
dc.subject.por.fl_str_mv |
competence contrast mylonitization fault nucleation and propagation folds formation transpression |
topic |
competence contrast mylonitization fault nucleation and propagation folds formation transpression |
description |
Fold-fault structures within a major transpressional shear zone of the SW Iberian Massif were investigated by combining geological mapping, cross-section analysis and microtectonic studies. A significant example of contractional deformation is displayed in the Portalegre-Esperanc¸a Shear Zone (PESZ) where a heterogeneous Ordovician stratigraphic sequence, showing a strong competence contrast between quartzites, slates and quartzo-feldspathic rocks favoured strain localization and fault nucleation that controlled fold formation. The presence of pelitic layers within the thick-bedded quartzites had probably provided weakness zones that were more favourable for the strain localization than the previous foliation present in the quartzites. The quartzites and the quartzo-feldspathic rocks (granites and volcaniclastic rocks) accommodated heterogeneous high strain developing different degrees of mylonitization. The quartzites with protomylonitic textures are dominant and represent coarse-grained siliciclastic sediments that suffered metamorphism and partial dynamic recrystallization. Ultramylonites occur within discrete high-strain shear zones. It is probable that the strain localization in the PESZ involved both the effect of having layers of different competence and layers or stratigraphic contacts with rocks that experienced grain size reduction dominated by cataclasis and dislocation creep. Folds within quartzites with sub-horizontal to gently plunging hinges vary from closed to open in thick-bedded quartzites and from tight to closed in thin-bedded quartzites. Observed changes in structural style of deformed quartzites, slates and quartzo-feldspathic rocks are interpreted to result from the constraints imposed by the mechanical properties of the different lithologies. As the folds tightened during shortening, the alternating zones of contrasting competence favoured the disruption of the bedding. The deformation history in the PESZ was dominated by thrusting and strike-slip faulting along incompetent layers that locally developed staircase geometry and transected the lower Ordovician stratigraphic sequence. The kinematic model proposed for the PESZ is consistent with the models of transpressional shear zones stretched along strike with the development of coeval strike-slip and low angle oblique-slip faults associated to active buckle folds with axes parallel to the principal extension direction |
publishDate |
2010 |
dc.date.none.fl_str_mv |
2010-01-01T00:00:00Z 2011-12-22T17:50:39Z 2011-12-22 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10174/2983 http://hdl.handle.net/10174/2983 |
url |
http://hdl.handle.net/10174/2983 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.relation.none.fl_str_mv |
521-535 45 Geological Journal mpereira@uevora.pt nd nd 250 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
collection |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
repository.mail.fl_str_mv |
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1799136467780370432 |