A snapshot of mid Eocene landscapes in the southern Central Andes: Spore-pollen records from the Casa Grande Formation (Jujuy, Argentina)

TAPIA, MARIANO J.; FARRELL, EZEQUIEL E.; MAUTINO, LILIA R.; DEL PAPA, CECILIA; BARREDA, VIVIANA D.; PALAZZESI, LUIS

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2023 vol. 18 p. 1 - 18

1932-6203

The southern Central Andes–or Puna–now contains specialized plant communities adaptedto life in extreme environments. During the middle Eocene (~40 Ma), the Cordillera at theselatitudes was barely uplifted and global climates were much warmer than today. No fossilplant remains have been discovered so far from this age in the Puna region to attest to pastscenarios. Yet, we assume that the vegetation cover must have been very different fromwhat it looks today. To test this hypothesis, we study a spore-pollen record from the midEocene Casa Grande Formation (Jujuy, northwestern Argentina). Although sampling is preliminary, we found ~70 morphotypes of spores, pollen grains and other palynomorphs,many of which were produced by taxa with tropical or subtropical modern distributions (e.g.,Arecaceae, Ulmaceae Phyllostylon, Malvaceae Bombacoideae). Our reconstructed scenario implies the existence of a vegetated pond surrounded by trees, vines, and palms. Wealso report the northernmost records of a few unequivocal Gondwanan taxa (e.g., Nothofagus, Microcachrys), about 5,000 km north from their Patagonian-Antarctic hotspot. With fewexceptions, the discovered taxa–both Neotropical and Gondwanan–became extinct fromthe region following the severe effects of the Andean uplift and the climate deterioration during the Neogene. We found no evidence for enhanced aridity nor cool conditions in thesouthern Central Andes at mid Eocene times. Instead, the overall assemblage represents afrost-free and humid to seasonally-dry ecosystem that prevailed near a lacustrine environment, in agreement with previous paleoenvironmental studies. Our reconstruction adds afurther biotic component to the previously reported record of mammals