Portal de Periódicos da CAPES

Benito Juárez County

2016; Springer Nature; Linguagem: Inglês

10.1007/978-3-319-39457-2_3

2197-960X

Patricia Eugenia Zalba, Martín Eduardo Morosi, M.S. Conconi,

Paleontology and Stratigraphy of Fossils

In the Benito Juárez County, four sectors will be considered: El Ferrugo and Constante 10-El Cañón Sector; Villa Cacique Sector; Sierra La Juanita Sector and Cuchilla de Las Aguilas-Sierra de La Tinta Sector. Crystalline basement rocks have been altered by weathering processes, resulting, from bottom upwards in: bedrock, saprock, saprolite and, occasionally, in two superimposed paleosols. Argillized basement rocks are covered by a highly resistant conglomerate of the Balcarce Formation. Weathering profiles are analized in detail. Mineralogical composition, by X-ray diffraction of the clays of El Ferrugo and Constante 10 is similar. Also, these deposits are similar to those of La Verónica and Santa María, described in Chap. 2 . According to the technological characteristics of the clays of El Ferrugo and Constante 10-El Cañón Sector they are classified as “Fire clays”. In the Villa Cacique Sector the Olavarría Formation, followed by the Loma Negra Formation and overlaid by the Cerro Negro and the Balcarce Formation, are described. The clays of the Cerro Negro Formation are composed of detrital illite and diagenetic clay minerals. Chemical and technological analyses attest to low values of PCE. The clays are classified as varied clays (wide-ranging). At the Sierra La Juanita Sector, the Villa Mónica Formation overlies unconformably the crystalline basement rocks and has been exploited for the ceramic industry. In the last years the Villa Mónica Formation has been redefined as carbonate, mixed, both with quartz megacrystals, and hetherolitic facies; their origin is explained and a paragenetic sequence is proposed. MISS are described in siliciclastic and mixed facies of the Villa Mónica Formation. SEM of the clay deposits and paleoenvironmental conditions of the Villa Mónica Formation are discussed. The Villa Mónica Formation age is considered to be Riphean, on the basis of the type of stromatolites. Technologically, clays from the Villa Mónica Formation are classified as plastic clays. In the Cuchilla de Las Aguilas and Sierra de La Tinta Sector the sedimentary sequence overlying the basement rocks is represented by the Sierras Bayas Group covered by the Las Aguilas Formation and the latter, in turn, by the Balcarce Formation. Alunite provided a Middle Permian age according to K–Ar dating (telogenetic stage). MISS are described in the Las Aguilas Formation. Plastic clays, with refractory and semiplastic varieties, are used in red ceramic and cement industry.