Silurian and lower devonian chitinozoan biostratigraphy of the paraná basin in brazil and Paraguay

Abstract

The taxonomy and distribution of Chitinozoa from Silurian (Llandovery) and Lower Devonian strata are reported from the Paraná Basin in southern Brazil and eastern Paraguay. The preCarboniferous sequences of the Paraná Basin in this area are present in three sub-basins viz., the Alto Garças (north) and Apucarana (south) sub-basins in Brazil, and the "East Paraguay Sub-basin" in east Paraguay. There is more similarity in the lithology between the Alto Garças and "East Paraguay" subbasins, than between the former and the Apucarana sub-basin. Llandoverian and Lochkovian to Pragian beds are present in all sub-basins. So far, no Emsian beds have been found in outcrops from the north-northwest margin of the Alto Garças Sub-basin, and no early Emsian beds in the outcrops on the northeast margin. Furthermore, Emsian beds could not be identified from the "East Paraguay Sub-basin" in the present study. The Early Devonian sequence is more complete in the Apucarana Sub-basin. It seems that the Apucarana Sub-basin endured a different evolution compared to the two other sub-basins during the Ordovician, Silurian and lower Devonian. Of the 39 chitinozoan species encountered, 24 species are left in open nomenclature, and the following five species are newly described: Ancyrochitina paranaensis, Angochitina daemoni, Sphaerochitina silurica, Spinachitina harringtoni, and Spinachitina wolfarti. A chitinozoan biozonation, with five zones and three subzones, is proposed for the investigated interval, and compared with the spore zonation. In addition we infer that the Furnas Formation could correspond to two chitinozoan zones found in Bolivia and Argentina (zones of Urochitina loboi and Angochitina aff. A. comosa), ranging in age from late Lochkovian to earliest Pragian. The zones are, from oldest to youngest: total range zone of Belonechitina postrobusta (upper Rhuddanian); total range zone of Conochitina elongata (Aeronian); concurrent range subzone of Spinachitina wolfarti n. sp. and Plectochitina sp. A (lower Aeronian); concurrent range subzone of Conochitina proboscifera and Spinachitina harringtoni n. sp. (upper Aeronian s.l.); concurrent range subzone of Conochitina proboscifera and Desmochitina cf. D. densa (lower Telychian s.l.); concurrent range zone of Salopochitina monterrosae and Conochitina proboscifera (upper Telychianlower Sheinwoodian); total range zone of Urochitina loboi (upper Lochkovian); total range zone of Angochitina aff. A. comosa (lowermost Pragian); total range zone of Ramochitina magnifica (Pragian s.l.), and total range zone of Ancyrochitina parisi (upper Emsian).

The Furnas/Ponta Grossa contact and the age of the lowermost Ponta Grossa Formation in the Apucarana Sub-Basin (Paraná Basin, Brazil): integrated palynological age determination

“…About 2.7 km north of Amorinópolis city (Figure 1) in the northeastern part of the Alto Garças Sub-basin, chitinozoans have been described from a level ca. 1 m above a conglomerate between the Furnas and Ponta Grossa (= Chapada Group unit 2 sensu equivalents (Grahn et al, 2000. This is in agreement with the lowermost Chapada Group unit 2 in well RVR-1 (Figure 1; Mauller et al, 2009), where a sample ca.…”

“…The chitinozoans constitute a characteristic latest Emsian assemblage with species such as Ancyrochitina sp. B sensu Grahn, 2000, Angochitina daemoni, and Ramochitina ramosi. These species also occur in the Tibagi Member of the Ponta Grossa Formation, as defined in the Tibagi-Telemâco Borba section (Bergamaschi, 1999;Grahn et al, 2000).…”

“…Outcrops with a continuous sedimentary record over the Furnas/Ponta Grossa (or Ponta Grossa equivalents) contact are known from many localities in the Paraná Basin (Figures 1-2; for references see Grahn et al, 2000Pereira, 2000;Mauller et al, 2009). Published information of lithologies is also known from several Petrobras wells (e.g.…”

“…Published information of lithologies is also known from several Petrobras wells (e.g. Lange, 1967;Bergamaschi, 1999;Grahn et al, 2000; Gaugris & Grahn, 2006). Most of these localities display an arenaceous or silty facies in the lowermost part of the Ponta Grossa Formation in the Apucarana Sub-basin.…”

About Echinoderms of the Devonian of the Paraná Basin: Faunal Turnovers and Implications for Bioestratigraphic Utility

“…O Devoniano da Bacia do Paraná aflora em faixas relativamente estreitas nas bordas leste e noroeste, nas sub-bacias de Apucarana e Alto Garças, respectivamente, sendo recoberto por rochas mesozoicas na maior parte da área da bacia (Petri & Fúlfaro, 1983 Grahn et al, 2000Grahn et al, , 2013Bosetti et al, 2012). Essa nova interpretação é usada no presente trabalho.…”