Cretaceous angiosperm pollen from the Kachaike Formation, south-western Santa Cruz Province, Argentina

Abstract

Thirty-three angiosperm pollen species are here reported from mid-Cretaceous deposits of the Kachaike Formation, Austral Basin, southern Argentina. Clavatipollenites is the most abundant angiosperm genus, with six well-defined morphological groups recognised on the basis of their reticulum morphology and sculpture. Pollen of eudicots are scarce, represented by tricolpate (Psilatricolpites spp. and Tricolpites spp.), tricolporoidate and tricolporate morphotypes (Dryadopollis spp.). Increasing complexity in the aperture structure is seen throughout the sequence; tricolpate and tricolporoidate forms are recorded in almost all samples, while tricolporate pollen grains are restricted to the middle and upper levels of the unit. The high species richness and abundance of monocolpate-ulcerate angiosperm related to monocots or magnoliids sensu lato recorded in the unit is comparable to that previously recognised in other assemblages from the early and middle Albian of the southern (e.g. Australia) and northern hemispheres (e.g. Western Portuguese basin, Europe). The recorded increase in the number of angiosperm species towards the middle and upper parts of the Kachaike Formation, with the presence of monocolpate, tricolpate, tricolporoidate and tricolporate pollen, suggests an early-early middle Albian age for these parts of the unit, in agreement with the early Albian age proposed for its basal levels on the basis of dinoflagellates.

Keywords:

• Angiosperm pollen
• Cretaceous
• southern South America

Acknowledgements

We kindly thank the detailed reviews made by Dr. J. Doyle and Dr. P. Hochuli, whose comments and suggestions greatly improved the final version of the manuscript. We are grateful to O. Cárdenas, L. Villar de Seoane and F. Tricárico for sample preparations and work with SEM.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This investigation was supported by the Projects BID-Conicet [PICT 433/07], [PICT 2010/528]; CONICET [PIP 679], [PIP 0512], [PIP 0286].