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Chlorococcalean algae as palaeoenvironmental indicators: new data from the Los Rastros Formation, Triassic of central-western Argentina

2006; Museo Argentino de Ciencias Naturales Bernardino Rivadavia e Instituto Nacional de Investigación de las Ciencias Naturales; Volume: 8; Linguagem: Inglês

10.22179/revmacn.8.321

1853-0400

Eduardo G. Ottone, Adriana Cecilia Mancuso,

Plant Diversity and Evolution

Chlorococcalean algae as palaeoenvironmental indicators: new data from the Los Rastros Formation, 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 palynological assemblage of miospores and Chlorococcalean algae. The miospore association is characterized by a relative abundance of corystosperm pollen grains with subordinate spores and inaperturates, diploxylonoid disaccates, monocolpates, monosaccates and striate pollen grains. The phytoplankton is represented by the Chlorococcalean Botryococcus and Plaesiodictyon. Geological data and variations in phytoplankton content indicate that the lacustrine system should be moderately eutrophic towards the lower third of the section, evolving into a body with oligotrophic conditions through the middle and upper part of the unit. Comparisons with the Río Gualo section suggest palaeoenvironmental similarities between the two areas. One new disaccate pollen grain species, Platysaccus rhombicus, is proposed.