Effects of base level change, paleoenvironmental and faciological controls on palynological associations from the final stages of the LPIA in southwestern Gondwana

Abstract

Insights on paleoenvironmental, faciological and stratigraphic influence in Gondwanan Permocarboniferous glacial and terminal glacial palynofloral successions are provided by new numerical data recovered from drill core sections encompassing the upper Itararé Group, in southwestern Paraná Basin, Brazil. High resolution sampling from a composite section, consisting of four successive boreholes, allows the recognition of the Pennsylvanian Crucisaccites monoletus Zone (CmZ) and the Permian Vittatina costabilis Zone (VcZ). The main quantitative features of spore-pollen assemblages are subject to a high degree of paleoenvironmental, faciological and stratigraphic control, characterizing four distinct palynological intervals. Correlation of palynological and sedimentological data observed along the studied section is tested with the application of multivariate cluster analysis, which suggests that marked shifts in dominance of certain sporomorph genera coincide with stratigraphic surfaces limited by cycles and subcycles of glacier advance and retreat. Oscillations in the quantitative trends of the studied assemblages are interpreted as the result of multiple factors affecting the palynofloral record in the context of a glacio-marine environment from the final stages of the LPIA, which is confirmed by the presence of microplanktonic elements in addition to lithological data. Among the major recognized aspects to exert influence upon the overall composition of palynofloral assemblages are the phytogeographical distribution of particular plant taxa, climate change and sedimentary environments/facies. Gaps in the sedimentary record caused by base level oscillations are directly correlatable to surfaces of sudden palynological change. Additionally, evidence suggests that regressive-transgressive trends could have an effect in the pollen/spore proportions of palynofloral successions.