Palinoestratigrafia e paleoecologia da Formação Taciba (Grupo Itararé) na região de Ibaiti-PR, nordeste da Bacia do Paraná

Abstract

The Itarare Group, the Permocarboniferous unit of the brazilian Parana Basin, encloses the record of the most prominent and widespread glaciation of the Phanerozoic Eon, the Late Paleozoic Ice Age (LPIA). Despite holding the thickest and geographically more extensive record of the referred glaciation, the Itarare Group has scarce marine fossils with biostratigraphic potential and a few absolute age data, what hamper regional correlation with another gondwanic basins. In this sense, the palynology is the main tool for age control and stratigraphic correlation in this unit, in spite of its low resolution. This work aims to contribute with the palynological knowledge of the last stages of the LPIA (Taciba Formation) in the northern Parana Basin. For this, three samples of muddy facies were collected in two distinct outcrops in the Ibaiti region (northeast Parana State) and analyzed according to the recommended methods for paleozoic samples. The samples revealed a relatively abundant and diverse palynological assamblage constituted by a total of 35 sporomorphs that includes 19 spores, 16 pollen grains and 7 microplancton elements. The most abundant taxa consist of cingulizonate ( Vallatisporites and Cristatisporites ) and apiculate ( Horriditriletes ) spores in addition to taeniate bisaccate pollen grains (Protohaploxypinus and Illinites). Subordinate taxa include monosaccate ( Cannanaropolis and Plicatipollenites ) and non-taeniate bisaccate pollen grains ( Limitisporites ) along with microplancton elements. These latter encompasses some diagnostic taxa of marine environment, as algae Tasmanites sp. , Deusilites tenuistriatus , Leiosphaeridia sp. and Navifusa variabilis. Four paleoecological associations defined for the Ibaiti palynological assamblage indicated that at the time of deposition of the upper Itarare Group, parent plants occupied distinct landscape positions, from flat areas partially or totally flooded to mountain regions. The identified species correlate with the Protohaploxypinus goraiensis Subzone of the Vittatina costabilis Interval Zone (VcZ), mainly based on the presence of Protohaploxypinus limpidus , Illinites unicus and Vittatina subsaccata . Moreover, palynology placed deposition of the last deglacial episode in northern Parana Basin in the early Permian (Early Cisuralian), age that is attributed to the Protohaploxypinus goraiensis Subzone.