A case of pore mounds in Paleogene buliminids from the Austral Basin, Argentina

Abstract

Pore mounded (mamelones centralmente perforados) wall texture is characterized by the accumulation of shell material around pores, creating mound structures described as a typical wall texture often present in serial planktonic foraminifera such as the Santonian-Paleocene triserial genus Guembelitria. A surface wall texture with well developed and distinctive pore mounds is also recorded in the Austral Basin in two phylogenetically related buliminid species, Bulimina fueguina Malumián and "Kolesnikovella" severini (Cañón and Ernst). Both species have no adequate generic assignment and both are frequent and apparently endemic to the Austral Basin. The former has three chambers per whorl and is mostly recorded in the late middle Eocene, and the latter one, exhibits a tendency to have two chambers per whorl and is recorded in the late Eocene. Although rare, pore mounds are also known from other buliminid species elsewhere, thus being apparently associated to buliminid taxa among benthic foraminifera. This association seems consistent with the buliminid ancestors proposed for the modern triserial planktonic foraminifera, based on genetic studies, as well as for Cretaceous serial planktonic foraminifera, based on morphological and stratigraphical grounds.Simposio II: El Paleógeno de América del Sur y CentralFacultad de Ciencias Naturales y Muse