Palinología y paleoambientes en el perfil de Bajo Comisión (Cretácico), provincia de Santa Cruz, Argentina

Abstract

Palynology and paleoenvironments of the Bajo Comisión section, Cretaceous of Santa  Cruz province, Argentina. A section at the classical locality Bajo Comisión, originally studied by T. Halle, has provided new stratigraphical data. More than 200 palynological species assigned to the Albian have been determined. They were recovered in 16 fertile horizons along the 272 m thick column. The three lower fertile horizons  are referred to the Río Mayer Formation while the other levels belong to the Kachaike Formation. Counts of the main palynological groups include a marine sector in the lower half of the profile. Pteridophytes (abundant Anemiaceae) and ymnosperms (mainly Classopollis ) dominate throughout the column, while angiosperms are

represented by scarce and moderately varied primitive types. The environment was dominated by deltaic sedimentation (prodelta-deltaic front-subaqueous plains) with a moderate marine influence in the lower part of the column, becoming typically continental (sub-aerial- fluvial) at the upper half of the section. The stratigraphic distribution of 80 selected species shows a gradual and constant change in the composition of the palynological assemblage. Two main biostratigraphic units are characterized by first and last appearences of several taxa.

Further subdivisions that may have biostratigraphic significance are also suggested. Finally, comparisons with other palynofloras of the Austral Basin in Santa Cruz province, are made