"Tectônica rúptil mesozóico-cenozóica na região da Serra dos Órgãos, RJ" / "Mesozoic-Cenozoic brittle tectonics of the Serra dos Órgãos range, RJ"

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Mezosoic-Cenozoic brittle tectonics of the Serra dos Órgãos range in the Rio de Janeiro State, southeastern Brazil, was investigated using morphostructural analysis and field surveys. The study area is a sector of the Serra do Mar coastal range, with summits over 2.200 m a.s.l., and is included in the central segment of the Neoproterozoic-Cambrian Ribeira Belt, where metassedimentary and several generations of granitoid rocks occur. Integrated analysis of digital elevation models, morphometric maps, lineaments, brittle structures and distribution of lithotypes, and comparison with the regional tectonic context of Southeastern Brazil, allowed us to admit that the main brittle features observed in the region are related to six superimposed brittle tectonic regimes. The first tectonic regime, of Neoproterozoic-Cambrian age, was characterized by left-lateral E-W-trending strike-slip, with NE-SW compression and NW-SE extension. Similar regimes were active during Early Cretaceous and Late Cretaceous to Paleocene, when they were responsible, respectively, for the emplacement of basic dykes swarm of the central-western portion of Rio de Janeiro State, and of the intrusive centers and alkaline dykes along the Cabo Frio Magmatic Lineament. This regime caused intense and widespread NE-SW-trending fracturing throughout the study area. During the Eocene, a NW-SE-trending extensional regime, considered as generator of the Continental Rift of Southeastern Brazil, operated in the region. It was responsible for the relief segmentation in the south-southeast part of the area, where NE-SW-trending elongated blocks in a step-like array descending to the southeast are observed. At the same time occurred the deformation of an old erosion surface, which had previously leveled the summit of the Serra dos Órgãos range at around 2.000 m a.s.l. The next tectonic regime is related to a NW-SE Late Pleistocene-Holocene compression which have reactivated NW-SE-trending fractures as normal faults, partially preserved as trapezoidal facets in the landscape. The last tectonic regime recorded in the region finds correspondence with an E-W Holocene compression.

ASSUNTO(S)

serra dos Órgãos range mesozóico-cenozóica brittle tectonics mesozoic-cenozoic paleostress. tectônica rúptil serra dos Órgãos morfometric analysis análises morfométricas paleotensões.

ACESSO AO ARTIGO

Documentos Relacionados