The ordovician-silurian sequence of the Paraná Basin

Abstract

Although it constitutes one of the most studied themes of Brazilian geology. the stratigraphy of the
Paraná Basin in its Brazilian portion only included Silurian age strata in the ear/y 80's, with the mapping and definition
of the Vila Maria Formation in its northern portion. From then on a few works were directed at identifying the preDevonian package in subsurface sections, and to the establishment of the distribution of these sediments throughout
the basin. At the same time biostratigraphic studies established a Llandoverian age for the marine fossiliferous pelites
of the Vila Maria Formation. The present study is based on the identification of the basal pre-Devonian units of the
Paraná Basin by its lithological characteristics, gamma ray patterns in profiles, and microfossil contentoThe area of
occurrence of the Ordovician-Silurian sequence was redefined at the basin scale, as well as it was established a new
correlation of these units in the Brazilian portion of the basin with its equivalents in Paraguay. the area where important
type sections of this package occurs. Furthermore , new results of the biostratigraphic investigations on samples of
fossiliferous horizons of Brazilian and Paraguayan wells are included in order to give support to the stratigraphic study
carried out.