%0 Journal Article
%T Caracterizaci¨®n de calcretes de la Formaci¨®n Puerto Yeru¨¢ (Cret¨¢cico), en base a su micromorfolog¨ªa (Entre R¨ªos, Argentina)
%A Tofalo
%A Ofelia Rita
%A Pazos
%A Pablo Jos¨¦
%J Revista de la Asociaci£¿3n Argentina de Sedimentolog£¿-a
%D 2002
%I Scientific Electronic Library Online
%X calcretes have been reported from the cretaceous successions present in the mesopotamia of argentina, which are exposed along the right margin (fig. 1) of the uruguay river (entre rios province). those successions correspond to the puerto yeru¨¢ formation and their facies and aspects related to calcrete types have been analyzed in previous works (e.g. tofalo, 1986 a, b). however, the micromorphological and diagenetical characterization of calcretes remains unresolved. this paper attempts to determine the diagenetic processes related to their genesis, taking into account microfeatures such as fabrics and textures. the data set of this study consists of 30 samples comprising all calcrete types (nodular, massive, laminar and brecciated) distinguished from macroscopic observations in the field. some micro-features are present in all of calcrete types, such as alpha fabric (fig. 2a,b) and crystallaria (including circumgranular types) but others are typical of each type of calcrete. the alpha fabric is a dense and continuous mass of relict micrite, mainly recrystallised to microspar and spar, with floating etched skeletal grains of quartz, sandstone, volcanic ground-mass and paleosol fragments. it was generated by the replacive and displasive growth of micrite in the vadose zone from supersaturated carbonate solutions during periods of rapid evaporation. in a few cases, the host material is cemented by sparry calcite with well-developed cleavages and straight intercrystalline boundaries, suggesting precipitation in the phreatic zone (fig. 2c). nodular calcretes are characterized by alpha fabric containing isolated glaebules (orthic and disorthic) with variable size and shape (fig. 2d). nodules are a product of diffusion followed by precipitation and displasive growth of carbonate. a well-developed alpha fabric with minor clotted texture generated by the concentration of cryptocrystalline calcite and clay in a micritic matrix is diagnostic of the massive calcretes. laminar
%K calcretes
%K classification
%K micromorphology
%K microfabrics
%K diagenetic environment.
%U http://www.scielo.org.ar/scielo.php?script=sci_abstract&pid=S1853-63602002000200002&lng=en&nrm=iso&tlng=en