Resumen de Algas Chlorococcales como indicadores paleoambientales: nuevos datos de la Formación Los Rastros, Triásico del centro-oeste de Argentina
Eduardo Guillermo Ottone, Adriana C. Mancuso
Chlorococcalean algae as palaeoenvironmental indicators: new data from the Los RastrosFormation, Triassic of central-western Argentina. Lacustrine strata of the Los Rastros Formation(Triassic) at the Ischigualasto Provincial Park section, San Juan province, yield a distinctive palynologicalassemblage of miospores and Chlorococcalean algae. The miospore association is characterized by a relativeabundance of corystosperm pollen grains with subordinate spores and inaperturates, diploxylonoid disaccates,monocolpates, monosaccates and striate pollen grains. The phytoplankton is represented by the ChlorococcaleanBotryococcus and Plaesiodictyon. Geological data and variations in phytoplankton content indicate that thelacustrine system should be moderately eutrophic towards the lower third of the section, evolving into a bodywith oligotrophic conditions through the middle and upper part of the unit. Comparisons with the Río Gualosection suggest palaeoenvironmental similarities between the two areas. One new disaccate pollen grain species,Platysaccus rhombicus, is proposed.
