PALYNOLOGY OF THE LA VETEADA FORMATION IN ITS TYPE LOCALITY (LOPINGIAN), FAMATINA RANGE, LA RIOJA PROVINCE, ARGENTINA. SPORES

GUTIERREZ, P. R.; ZAVATTIERI, A.M.; EZPELETA M.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2017 p. 441 - 464

0002-7014

This is a systematic study of the palynological assemblages recorded in the upper part of the La Veteada Formation (La Veteada Assemblage), which constitutes the section of the type locality, La Rioja Province, Argentina. In this contribution, 38 species of trilete and monolete spores are described and/or illustrated. Two new species are described: Lundbladispora verrucosa sp. nov., and Secarisporites triangularis sp. nov., and also a new combination of Secarisporites imperialis (Jansonius) nov. comb. is proposed. The trilete spores are one of the dominant groups of the analized microflora reducing its frequency from the base to top of the section (from 32.2% to 14.5%). Dominate the cingulate-cavate spores (derived from herbaceous lycophytes) represented by species of the genera Densoisporites-Densosporites-Lundbladispora, and Secarisporites. Smooth and apiculate trilete spores (derived from ferns and sphenopsids) are represented by the genera Calamospora, Punctatisporites, Granulatisporites, Brevitriletes, Cyclogranisporites, Osmundacidites, Verrucosisporites, Raistrickia, Foveosporites, between others. The upper section of the Veteada Formation at its type locality was deposited in fluvial-lacustrine environments under arid to semiarid climatic conditions. Semiperennial hypersaline/brackish lakes dominate the sedimentation with periodic expansion and retraction episodes suggesting a low-relief setting. In the surrounding areas of these water-bodies dominated by evaporites grew the herbaceous vegetation mainly composed of the herbaceous lycopsids Isoetales, Selaginellales, Lycopodiales, and ferns. While in the flood-plain, herbaceous vegetation of pteridophytes (Filicales, Zygopteridales), bryophytes and herbaceous sphenophytes were developed along the river courses and in the surrounding areas of the freshwater bodies (ponds and small lakes). The presence of Densoisporites complicatus, D. nejburgii, D. playfordii, D. solidus, Leptolepidites jonkerii, Lundbladispora brevicula, L. obsoleta, L. springsurensis, L. wilmotii, Ringosporites fossulatus, Secarisporites bullatus, S. imperialis, and S. lacunatus allow confirming a Lopingian age for the upper section of the La Veteada Formation. Microfloras containing high proportions of lycopsid-tetrads are commonly recorded mainly in extra-gondwanic realm constrained to late Permian to early Triassic age.