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GEOLOGIA DO GRÁBEN DE MARTINÓPOLE, ÁREA DE CAMPANÁRIO/PAULA PESSOA (GRANJA, CE): IMPLICAÇÕES NA EVOLUÇÃO LITOESTR ATI GRÁFICA E TECTONOMETAMÓRFICA DO NOROESTE DO CEARÁ

1992; Sociedade Brasileira de Geologia; Volume: 22; Issue: 2 Linguagem: Inglês

10.25249/0375-7536.1992143156

2177-4382

Diógenes Custódio de Oliveira,

Geography and Environmental Studies

CEARÁ. The MartinópoleGraben is located in the Northwestern part of Ceará State.A reconnaissance geologic mapping in an area between Campanário and Paula Pessoa cities allowed the stablishement of a lithostratigraphic and tectonometamorphic evolution of this Graben (Table 1).Six major stratigraphic units have been recognized in the study area (from bottom to top): Gnáissico-Migmatítico Complex, Martinópole Group, São José Group, Casinha Metasediments, and Jaibaras Group.The Gnáissico-Migmatítico Complex underlies all other units and is characterized by an additional deformational phase (D n-1 ) which is not present on the Martinópole Graben.The São Joaquim Formation was excluded from the Martinópole Group due to its highly complex pattern of deformation and its different metamorphic grade (upper amphibolite with intermediate pressure facies potassium feldspar/sillimanite isograde and kyanite isograde).On the other hand within the Graben, the rocks have pointed out metamorphism in prehnite-pumpellyite facies(kaolinite + 2quartz X pyrophyllite + H 2 O) to green schist facies (chlorite/biotite isograde or on the upper part of the stability of pyrophyllite).The Martinópole Group has been defined as a volcanoclastic unit, also containing minor amounts of volcanic and siliciclastic rocks.This group remains with the two original formations: Covão (bottom) and Santa Terezinha (top).The São José Group, which is distinguished by very low-grade metamorphic claystones and sandstones has an uncertain stratigraphic relationship with the Martinópole Group; the informal unit named Casinha Metasediments consists of diamictites with a pre-foliate pebbly framework.It can be correlated with the Olho d'Agua do Caboclo Formation (as defined by Hackspacher et al. 1988).The Jaibaras Group filled small pullapart basins and comprised molassic clastic wedges, that are represented by Massapé Formation conglomerates and by the fine clastic rocks of the Pacujá Formation, (both are Brazilian in age).All the units underwent several pulses of shear/faulting with different magnitudes, deformational mechanisms and age.