The earliest Ostracoda record from Brazil: Vila Maria Formation, Rio Ivaí Group, Paraná Basin, Central Brazil

Abstract

-Two species of Ostracoda are described for the first time from the parastratotype-section of Vila Maria Formation; this section is 30 m thick, located on the northern border of the Paraná Basin. The Vila Maria Formation records the Upper Ordovician-Lower Silurian boundary of the Paraná Basin in Bom Jardim de Goiás, State of Goiás, central Brazil. The new species represents the earliest Ostracoda occurrence from Brazilian strata. Delicate internal and external molds of isolated valves are abundant in the basal portion of the parastratotype-section of Vila Maria Formation. This interval comprises black shales that record post-glacial marine transgression, overlapping the Upper Ordovician glacial sequence of the Iapó Formation. The paleogeographic reconstruction indicates that deposition of the basal portion of the Vila Maria Formation took place in high-latitude, cool water conditions at the margin of Gondwana, under similar environmental conditions to the Djeffara Formation in the Ghadames Basin and the Tichitt Group in the Taoudeni Basin, both in the Northern Africa.Key words: Ostracoda, Ordovician, Paraná Basin.RESUMO -Duas espécies de Ostracoda têm ocorrências inéditas descritas a partir da seção-tipo suplementar da Formação Vila Maria, seção que tem 30 m de espessura, localizada na borda norte da Bacia do Paraná. A Formação Vila Maria está posicionada no limite Ordoviciano Superior-Siluriano inferior da Bacia do Paraná na região de Bom Jardim de Goiás, Estado de Goiás, Brasil central. As novas espécies descritas representam a ocorrência mais antiga de Ostracoda de estratos brasileiros. Moldes internos e externos de valvas isoladas são abundantes na porção basal da seção-tipo suplementar da Formação Vila Maria. Este intervalo é constituído por folhelhos pretos representando a transgressão marinha pós-glacial, sobrepostos aos diamictitos da Formação Iapó, que representa a sequência glacial do Neordoviciano na Bacia do Paraná. A reconstrução paleogeográfica indica que a deposição da porção basal da Formação Vila Maria ocorreu sob condições de altas latitudes e águas frias na margem de Gondwana, onde atualmente se localiza a América do Sul, sob condições semelhantes àquelas das Formações Djeffara na Bacia de Ghadames e Tichitt Group na Bacia do Taoudeni onde atualmente se localiza a porção norte da África.Palavras-chave: Ostracoda, Ordoviciano, Bacia do Paraná.

The first record of Hirnantian Ostracoda in South America: implications for the biostratigraphy and paleozoogeography of the Paraná basin

“…The methodology for extraction of ostracodes from rock samples followed Adôrno et al (2016): First, they were separated from the main bulk of samples by hand cutting ∼0.3 cm 3 blocks containing specimens. After that, each specimen was excavated from its blocks and cleaned with 1 mm syringe needles under a Leica ES4 stereoscopic microscope.…”

“…The taxonomy of Harpabollia harparum (Troedsson, 1918) and Satiellina paranaensis Adôrno and Salas in Adôrno et al, 2016 as well as their stratigraphic and paleozoogeographical Gonçalves et al-First record of Hirnantian Ostracoda from Brazil distribution are presented here. Supraordinal and ordinal taxonomies follow Liebau (2005) while the subordinal taxonomy is based on Mohibullah et al (2013).…”

“…Family incertae sedis Genus Satiellina Vannier, 1986 Type species.-Bollia delgadoi Vannier, 1983(Vannier, 1986, by original designation. (Adôrno et al, 2016).…”

“…Occurrences of Satiellina paranensis and Conchoprimitia brasiliensis Adôrno and Salas in Adôrno et al, 2016 in shale levels at the base of the Vila Maria Formation, which overlies the Iapó, imply an Ordovician age for both the Iapó and lowermost Vila Maria formations because Satiellina Vannier, 1986 andConchoprimitia Öpik, 1935 are restricted to the Ordovician Period. Coupled with the absence of an unconformity between the Iapó and Vila Maria formations, as well as the presence of glacial diamictite strata, this feature suggests a Hirnantian age for the interval (Adôrno et al, 2016). However, no index fossil typical of the Hirnantian has been observed in the Iapó-Vila Maria transition until now.…”

Chronostratigraphy and environment of Furnas Formation by trace fossil analysis: Calibrating the lower Paleozoic Gondwana realm in the Paraná Basin (Brazil)

“…The Rio Ivaí Group records deposition in fluvial to shallow marine environments (Alto Garças Formation), glacial-marine settings (Iapó Formation), and offshore marine realms (Vila Maria Formation) (Assine et al, 1998a(Assine et al, , 1998b. Palynomorphs and marine macroinvertebrate body fossils indicate a Late Ordovician to Early Silurian (early Llandovery) age for the Iapó and Vila Maria formations (Assine et al, 1994;Popp et al, 1981;Burjack and Popp, 1981;Faria, 1982;Gray et al, 1985;Rodrigues et al, 1989;Borghi et al, 1996;Adôrno et al, 2016).…”