Paleofloristic biozonation and chronostratigraphy of the Argentine Triassic

A paleobotanical biozonation and a chronostratigraphic chart for the contin ental Triassic of Argentina are proposed. The biostratigraphic study was ba sed on the multivariate analysis of 218 taxa distributed in 15 lithostratig raphic units and 134 taxa from 28 paleocommunities. The biostratigraphic an alysis was also supported on the Permian or Jurassic lineage of several spe cies, their acme, the temporal turnover and the evolution of the paleoflora s. This information was evaluated together with the stratigraphic location of the fossiliferous horizons, the geochronologic information and the relat ionship between paleocommunities and sedimentary facies and environments. F ive biozones were defined: 1. Dictyophyllum castellanosii, Johnstonia stelz neriana and Saportaca Biozone (CSD). Represented by a mixed forest and iden tified in the Barreal and Ischichuca Formations. 2. Yabeiella mareyesiaca, Scytophyllum bonettiae and Protophyllocladoxylon cortaderitaensis Biozone ( MBC). Mixed forests recognized in the Potrerillos, Cortaderita (lower secti on) and El Alcazar Formations. 3. Yabeiella brackebuschiana, Scytophyllum n euburgianum and Rhexoxylon piatnitzkyi Biozone (BNP). Mixed forests, identi fied in the Vera, Potrerillos and Ischigualasto Formations, and in the El T ranquilo Group. 4. Dicroidium odontopteroides and D. lancifolium Biozone (O L). Represented by a herbaceous and shrub-like paleocommunity, defined in t he Cacheuta Formation and in the upper section of the Cortaderita Formation . 5. Dictyophyllum tenuiserratum, Linguifolium arctum and Protocircoporoxyl on marianaensis Biozone (DLM). Deciduous and mesoxerophytic forests, identi fied in the Los Colorados and Rio, Blanco redbeds, the Paso Flores Formatio n and the Tronquimalal Group. The following local stages are defined on the bases of biozone chronology, analysis of the main stratigraphic unconformi ties and evolution of the basin infill: Barrealian (Early to Middle Triassi c), Cortaritian (late Middle to early Late Triassic) and Florian (upper Lat e Triassic).