Aspectos tafonômicos das formações Pimenteira (Membro Picos) e Longá, Devoniano Médio e Superior da Bacia do Parnaíba, estado do Piauí, nordeste do Brasil

Abstract

Since the first work conducted to the Pimenteira Formation during the second half of the 20th century, scientific studies have focused mostly in the geological and taxonomical aspects of this formation, leaving the analysis of taphonomic signatures regarding the Devonian assemblages of the Parnaíba Basin aside. To date, the analysis of taphonomic signatures of macrofossils in the Parnaíba Basin were restricted to works developed based on macroinvertebrates and plant fragments collected in four outcrops of the Passagem Member (Oiti, Rio Bangue, BR-316/Km 305 and Barreiro Branco), in the state of Piauí. Two of the other Devonian units in the Parnaíba Basin (Picos Member of the Pimenteira Formation and Longá Formation) are studied herein for the first time, through the description of the taphonomic attributes of its macroinvertebrates assemblages, carrying on the taphonomic studies within this region. The main objective of this thesis is to promote a taphonomic analysis of the Riachão, Itainópolis, Sussuapara, Morro Branco de Kegel, Pimenteiras 2, Pimenteiras 3, Picos 2, Picos 3, Mucambo, Capelinha 1, Capelinha 2 and Capelinha 3 (Picos Member), and Fazenda Barreiras outcrops (Longá Formation), integrating taphonomic and stratigraphic data, based on the informatin extracted from the fieldnotebooks. Based on the analysis of each outcrop, four differente types of fossil assemblages were identifed: autochthonous-paraauthochtonous (Riachão, Pimenteiras 2, Fazenda Barreiras), paraauthochtonous (Sussuapara, Picos 2, Picos 3, Mucambo, Pimenteiras 3), paraautochthonous-allochthonous (Itainópolis, Morro branco de Kegel e Capelinha 2), and allochthonous (Capelinha 1 e Capelinha 3). The result obtained from the taphonomic analysis indicates the prevalence of fossiliferous assemblages as paraautochthonous to allochthonous, and reinforces models previously discussed in the literature, which provides evidence and supports the great fluvial and deltaic influence in shallow marine environments.