Estilos Estruturais de bacias sedimentares

ESTILOS ESTRUTURAIS EM BACIAS SEDIMENTARES
- REVISÃO CONCEITUAL

Edison

José MILANI

Geólogo pela UFRGS (1977)
Mestre em Geologia pela UFOP (1985)
DEPEX/NEXPARISEINT
- Curitiba/PR

ABSTRACT

This article is an overview of applicable concepts concerning to the geometric characterization of structural assemblages commonly observed in sedimentary basins, also considering their genetic aspects in relation to plate tectonics.
The structural style of a specific geologic province is defined by the association of existing elements and their spatial arrangement. Its characterization affects the predictability of locating preferred areas for the occurrence of structures, which is highly desirable in expIoratory activity.
Based on key diagnostic characteristics, one can describe the predominant structural style of an area during a particular tectonic phase. As a criterion for classification in this case, use has been made of the spatial orientation of the stress field responsiblefordeforrnation, thereby recognizing:
a) compressional structural style, typical of the convergent boundaries of lithospheric plates; it is characteristic of foId beIts dominated by thrust faults;
b) transcurrent structuraI style, originating at conservative plate boundaries and characterized by a rich association of elements containing lateral displacement faults, thrust faults and normal faults, as well as folds, in a well-defined geometric arrangement;
c) extensional structural style, characteristic of divergent plate boundaries, the domain of normal faults that appear along grabens in areas where the continental crust is submited to rifting.

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INTRODUÇÃO

Os elementos estruturais de uma determinada região organizam-se segundo normas ditadas pelos campos de tensões atuantes quando de sua formação, estejam eles arranjados segundo um padrão geométrico bem definido ou em uma distribuição espacial aparentemente caótica.
Estes campos tensoriais são