Cohesive breccias and microbreccias in quartzites in the Buenos Aires ranges: Similitude, differences, and an approximation to their tectonic links

• Main Authors: Massabie, A.C., Nestiero, O.E., Sanguinetti, A.S.
• Format: Journal/Newspaper
• Language: unknown
• Subjects: Breccias; Fault rocks; Microbreccia cohesive; Sierras de Buenos Aires; breccia; deformation mechanism; extensional tectonics; fault zone; faulting; greenschist facies; metamorphism; outcrop; Precambrian; protolith; quartzite; tectonic setting; Argentina; Buenos Aires [Argentina]; Sierras Australes; Sierras Septentrionales; South America; South Atlantic Ocean
• Online Access: https://hdl.handle.net/20.500.12110/paper_00044822_v63_n2_p163_Massabie

Quartzitic sandstones of the sierras Bayas Group in Sierras Septentrionales of Buenos Aires are studied. Outcrops of these deformed rocks are observed at sierras Bayas and Barker localities, where quartzitic sandstones from Precambrian units are present. These rocks are compared with similar fault breccias in Sierras Australes of Buenos Aires, which were develop in quartzitic rocks of several Paleozoic units of this region. At both regions, fault zones are subvertical layers with acute contacts on the wall rocks. An original sedimentary protolith is recognized in textures and structures preserved in all samples of Sierras Bayas. Sedimentary textures at Sierras Australes are obliterated by penetrative deformation in greenschists facies methamorphism and also show a metaquartzitic protolith. In both analyzed regions, similar cataclastic textures are observed. All these breccias and microbreccias would be associated with a major extensional tectonic event of Jurassic - Cretaceous age, which could be related to the origin of Colorado and Salado extensional basins during the opening of the South Atlantic Ocean. Fil:Massabie, A.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Nestiero, O.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.