%0 Journal Article
%T Argilominerais da Formaˋˋo Cod車 (Aptiano Superior), Bacia de Graja迆, nordeste do Brasil
%A Gonˋalves
%A Daniele Freitas
%A Rossetti
%A Dilce de F芍tima
%A Truckenbrodt
%A Werner
%A Mendes
%A Anderson Conceiˋˋo
%J Latin American journal of sedimentology and basin analysis
%D 2006
%I Scientific Electronic Library Online
%X this work combines facies, stratigraphy, x-ray diffraction, sem and petrographic analyses in order to investigate argillaceous rocks of the cod車 formation exposed in the cod車 and graja迆 areas, northeastern brazil (fig. 1). the main goal is to characterize the clay mineral assemblage and record its variability along the depositional cycles in the attempt to discuss its origin and test its applicability as paleoclimatic and paleoenvironmental proxy indicators. the cod車 formation records the upper aptian deposition of the graja迆 basin, a tectonically subsiding structure originated during the early stages of rifting that culminated with the opening of the south atlantic ocean along the equatorial brazilian margin (aranha et al., 1990). this basin has been interpreted as a unique structure consisting of an intracontinental semi-graben, which was formed by combination of pure shear stress and strike-slip deformation (g車es and rossetti, 2001). the sedimentary successions of this basin include three depositional sequences, designated as s1, s2 and s3 (rossetti, 2001; fig. 2), with the first including the cod車 formation studied herein. the cod車 formation records a depositional system dominated by closed and hypersaline lakes and sabkhasalt pan complex (paz, 2000; paz & rossetti, 2001; paz & rossetti, 2005a). in the cod車 area, these deposits encompass a 25 m-thick prograding lacustrine succession arranged as shallowing-upward cycles that are attributed to central, transitional, and marginal lake facies associations. central lake deposits include mostly evaporites and bituminous black shales. transitional lake deposits consist of green to grey shales interbedded with limestones (lime-mudstone, laminated to massive peloidal wackestone to packstone and sparstone) formed in more oxygenated waters relative to the central lake deposits. marginal lake deposits include massive and indurated pelite with brownish-red colours, fenestral calcarenite of calcite grains, ostracodal wackesto
%K paleoclimate
%K paleoenvironment
%K clay minerals
%K late aptian
%K northeastern brazil.
%U http://www.scielo.org.ar/scielo.php?script=sci_abstract&pid=S1851-49792006000100003&lng=en&nrm=iso&tlng=en