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

摘要

In this systematic study of palynological assemblages from the upper part of the type section of the La Veteada Formation, 38 species of trilete and monolete spores are described and/or illustrated. Two new species are instituted: Lundbladispora verrucosa and Secarisporites triangularis, and a new combination Secarisporites imperialis (Jansonius) is proposed. Trilete spores comprise a dominant group in the analyzed palynoflora and show a reduced frequency from the base to the top of the section (from 32.2 to 14.5%). Cinguli-cavate spores (derived from herbaceous lycophytes) are dominant and represented by the genera Densoisporites, Lundbladispora and Secarisporites. Smooth and apiculate trilete spores (derived from ferns and sphenopsids) are represented by genera such as Calamospora, Punctatisporites, Granulatisporites, Brevitriletes, Cyclogranisporites and Osmundacidites. This upper section of the La Veteada Formation was deposited in fluvialhypersaline/brackish lacustrine environments under arid to semiarid climatic conditions. The areas surrounding these water-bodies dominated by evaporites were vegetated mainly by herbaceous lycopsids (Isoetales, Selaginellales, Lycopodiales) and ferns. Pteridophytes (Filicales, Zygopteridales), bryophytes and herbaceous sphenophytes were developed along the river courses and in the surrounding areas of freshwater bodies (ponds and small lakes) on the flood plain. The presence of Densoisporites complicatus, D. nejburgii, D. playfordii, D. solidus, Leptolepidites jonkeri, Lundbladispora brevicula, L. obsoleta, L. springsurensis, L. wilmotti, Ringosporites fossulatus, Secarisporites bullatus, S. imperialis and S. lacunatus confirm a late Permian (Lopingian) age for the upper La Veteada Formation. The palynofloras contain significant proportions of lycopsid tetrads; as is the case with many extra-Gondwanic strata of Lopingian/Early Triassic age.