Palynomorphs and facies associations of the Lagoa Azul Formation (Itararé Group, Pennsylvanian of the Paraná Basin), in southeastern Paraná State, Brazil

Abstract

In southeastern Paraná state, the Itararé Group rests through an angular unconformity over the preglacial substrate, composed of Precambrian to Devonian units which are increasingly older to the southeast. Because of this stratigraphic configuration, the outcrops of the Itararé Group in the Porto Amazonas region have been interpreted as representing its lowermost levels while those from the Campo do Tenente region, which are located more to the south, are considered to be younger. This paper presents the results of a palynological and facies analysis performed in seven outcrops from the lower portion of the Itararé Group (Lagoa Azul Formation) in the Porto Amazonas, Lapa and Campo do Tenente regions, aiming at the palynostratigraphic positioning. Nine sedimentary facies were identified, representing mostly mass-transport deposits and turbidites, deposited in a relatively deep marine environment under glacial influence. Palynological associations were recorded from all outcrops which are composed of scarce indigenous elements, comprising of spores and monosaccate pollen grains, with varied preservation degree. The general palynological features of the associations and the presence of certain species of spores and pollen grains suggest correlation to the Ahrensisporites cristatus Zone, which corresponds to the lower portion of the Itararé Group (Lagoa Azul Formation), of Pennsylvanian age (late Bashkirian to Kasimovian). The results corroborate the occurrence of glacial deposits of the lower Itararé Group in the outcrop belt. In addition, they demonstrate the importance of the study on processes of pre-Pennsylvanian palynofossils reworking and resedimentation.