Paleoenvironmental significance of the Family Anemiaceae in the Cretaceous of Brazil: inferences based on palynological data

Abstract

This paper discusses the paleoenvironmental value of the Family Anemiaceae from analyses of Cretaceous palynological assemblages containing spores belonging to the genus Cicatricosisporites. The analyzed samples are from Cretaceous units of several Brazilian sedimentary basins - Sanfranciscan Basin, Parnaíba Basin, Paraná Basin, Almada Basin and Pernambuco-Paraíba Basin. In the Areado and Codó formations, respectively from the Sanfranciscan and Parnaiba basins, the occurrence of terrestrial palynomorphs and abundant Classopollis pollen grains - isolated and in tetrads - indicates continental deposition close to the source area in a dry, hot climate. Cicatricosisporites, when not highly represented statistically in these formations, could suggest incompatibility with dry and hot conditions. However, some samples of the Codó Formation are characterized by the absence of Classopollis and the abundance of psilate and ornamented trilete spores - including Cicatricosisporites and Perotriletes. The latter suggests the existence of relatively humid periods with locally higher water availability. In the sample from the Bauru Group (Paraná Basin), only one specimen of Cicatricosisporites was observed among abundant ephedroid pollen grains (indicating an arid environment) and zonate and cingulate trilete spores (indicating a humid environment). This may suggest seasonal alternation in rainfall. In the Urucutuca (Almada basin) and Gramame (Pernambuco-Paraíba Basin) formations, the presence of palynoforaminifera and dinoflagellate cysts indicates marine depositional conditions, although continental palynomorphs co-occur. In the Urucutuca Formation, Cicatricosisporites constitutes the most abundant of the continental palynomorphs. We conclude that Cicatricosisporites can indicate a moderately humid climate from its frequent association with psilate and ornamented trilete spores and with Perotriletes, which indicates local standing water. Furthermore, Cicatricosisporites has generally low quantitative representation, when it occurs in association with indicators of dry climate.