New Palynological Data of the Cerro de las Cabras Formation (Middle Triassic) at its Type Locality, Mendoza, Argentina. Biostratigraphic and Phytogeographic Implications

Abstract

This palynological study presents a systematic update of the Cerro de Las Cabras Formation at its type section. Thirty-three genera and 81 species of palynomorphs are incorporated, including forms recorded for the first time in the Triassic of Argentina. Additionally, 53 forms of palynomorphs were synonymized with new or already known species of the unit from the taxonomic revision of previously published material. Four new combinations were proposed: Secarisporites argenteiformis, S. lobatoverrucosus, S. verrucosus and S. volkheimerii. The palynoflora is dominated by species of the Alisporites/Falcisporites, the Cycadopites/Monosulcites, the Secarisporites/Leptolepidites, and the Densoisporites/Lundbladispora complexes. The locally common presence of Illinites (∼14%), cf. Rimaesporites (∼4%), Minutosaccus (∼2.7%), Staurosaccites (∼2.3%), Protodiploxypinus (∼2%), Angustisulcites (∼1.7%), and Brachysaccus (∼1.7%) is noteworthy. The Permian taxa Cladaitina sp., Limitisporites rectus, Lueckisporites sp., Platysaccus sp. cf. P. trumpii, Protohaploxypinus goraiensis, Punctatisporites gretensis, and Retusotriletes sp. cf. R. nigritellus are interpreted to occur in situ. The common presence of typical north-central European species such as Illinites chitonoides and Illinites kosankei, along with the co-occurrences of Densoisporites playfordii, Angustisulcites gorpii, Ovalipollis notabilis, Samaropollenites speciosus, and Staurosaccites quadrifidus, enable the constraining of the age of the palynoflora to the late Anisian–early Ladinian. On the other hand, the present study reveals a greater number of species shared with the Northern Hemisphere and low-mid latitudes of Gondwana, including typical Onslow elements such as cf. Rimaesporites aquilonalis, Samaropollenites speciosus, Staurosaccites quadrifidus, and Minutosaccus crenulatus, which allow us to ascribe the studied assemblage to a mixed Onslow-Ipswich palynoflora.