Paleogene palynostratigraphy of the eastern middle Magdalena Valley, Colombia

Abstract

This work presents a detailed study of the pollen and spore distribution in the Paleocene‐Eocene Lisama and La Paz Formations on the eastern border of the Middle Magdalena Valley, Colombia. One hundred and forty‐seven samples obtained from cores and outcrops were prepared for palynological research, fifty‐nine of which were rich in pollen and spores. Three hundred spore and pollen taxa were identified. The studied stratigraphic interval is a 2000 m thick coastal and fluvial deposit formed in a variable subsiding tectonic setting. The Lisama Formation is characterized by the dominance of the Proxapertites group. Some typical Paleocene forms start to disappear toward the upper part of the Lisama Formation (e .g. Bombacacidites annae, Ephedripites vanegensis, Retidiporites magdalenensis), and are followed by a barren interval probably linked to intense oxidation during paleosol development (the uppermost 266 m of the Lisama Formation). In the La Paz Formation there is a progressive appearance of early and middle Eocene species (e.g. Cyclusphaera scabrata, Foveotriporites hammenii, Monoporopollenites annulatus, Perfotricolpites digitatus, Spirosyncolpites spiralis, Striatopollis catatumbus, Bombacacidites gonzalezii). This biostratigraphic evidence indicates that an early‐middle Eocene hiatus in the eastern area of the Middle Magdalena Valley basin is not present, as many authors have previously suggested. One new pollen genus, Foveomonoporites, and two new pollen species, Foveomonoporites variabilis and Psilamonocolpites operculatus are described and illustrated.