Early Eocene Spore and Pollen Assemblages from the Laguna del Hunco Fossil Lake Beds, Patagonia, Argentina

BARREDA, VIVIANA D.; ZAMALOA, MARÍA DEL CARMEN; GANDOLFO, MARÍA A.; JARAMILLO, CARLOS; WILF, PETER

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

Año: 2020 vol. 181 p. 594 - 615

1058-5893

Premise of research. The early Eocene Laguna del Hunco (LH) fossil site, northwestern Chubut Province,Argentina, holds one of the best-preserved and most diverse paleofloras worldwide. The paleoflora comprisesferns, gymnosperms, and flowering plants. Despite the rapidly growing knowledge of its macrofossil record, littleis known about the site?s palynological content. Herein, we present the first dispersed spore-pollen assemblagesrecovered from LH.Methodology. Palynological samples were collected from seven stratigraphic levels of the Tufolitas de LH(Huitrera Formation), of which six yielded palynomorphs. We determine the botanical affinities of fossilmorphotypes and provide systematic descriptions of some taxa. In addition, we establish similarities betweenLH and other Patagonian Eocene localities, and we compare palynological and prior megafloral records fromLH.Pivotal results. We identify 56 spore and pollen species and 28 plant families, of which eight (Cyatheaceae,Schizaeaceae, Polypodiaceae, Asteraceae, Chloranthaceae, Nothofagaceae, Rubiaceae, and Ulmaceae) are reliably reported from the site for the first time. Among other Eocene Patagonian palynofloras, the LH assemblageis similar to Pampa de Jones/Nahuel Huapi Este and Confluencia.Conclusions. The LH spore-pollen assemblages augment the plant fossil record for this significant Eocenelocality by incorporating new taxa (e.g., Asteraceae, with one morphotype that represents the oldest recordof the family in Patagonia). The new data also reinforce the presence of plant families previously reported frommacrofossils, such as Juglandaceae, with pollen grains similar to those of the Engelhardia-Alfaroa group, andFagaceae (Castaneoideae), complementing the macrofossil record of leaves and reproductive structures.