Maastrichtian palynoflora from north-central Patagonia, Argentina.

DE BENEDETTI, FACUNDO; MARÍA DEL C. ZAMALOA; GANDOLFO, MARIA A.; N. RUBEN CUNEO

Tucson, Arizona

Conferencia; Botany 2019; 2019

Botanical Society of America

During the Late Cretaceous, Southern South America was covered by extensive shallow epicontinental seas that gave place to a series of coastal plain sedimentary deposits representing estuaries, deltas, and lagoon/barrier complexes that, so far, are still poorly floristically understood. Among them, the La Colonia Formation deposits that outcrop in north-central Patagonia are providing abundant and critical information on the paleoenvironments and paleoclimate based on their paleobotanical and palynological components. The La Colonia paleoflora developed in freshwater coastal environments (lagoons or oxbow small lakes) featuring sporadic fine-grained sand beds associated with coastal sand bars. In this contribution, we report, for first time, a comprehensive palynological study of the La Colonia Fm. Among the most relevant palynomorphs are Quadraplanus brossus, Tubulifloridites lilliei, and Grapnelispora evansii that are representative of the Southern Hemisphere Proteacidites/Nothofagidites Province. We also identified the species Gabonisporis vigourouxii and Spinizonocolpites pollen-type which are distinctive species of the Late Cretaceous paleotropical Palmae Province. The presence of these taxa not only confirms the Maastrichtian age of the sediments but also allow the identification of the northern Patagonian Region within the Late Cretaceous Transitional (Mixed) Province. The composition of the La Colonia palynoflora (including palm pollen and other thermophilous taxa) supports humid, warm climatic conditions for the area during time of deposition.