Differences in Pennsylvanian - Cisuralian paleofloras in Bolivia and northern Argentina and its paleoclimatic and paleobiogeographic importance

DI PASQUO, M.M.

MENDOZA

Jornada; XXXVI Jornadas Argentinas de Botánica, XXVIII Reunión Anual de la Sociedad de Botánica de Chile y la II Reunión Científica de la Asociación Micológica Carlos Spegazzini; 2017

SAB

XXXVI Jornadas Argentinas de Botánica, XXVIII Reunión Anual de la Sociedad de Botánica de Chile y la II Reunión Científica de la Asociación Micológica Carlos Spegazzini (18-22 septiembre, Mendoza). Boletín de la Sociedad Argentina de Botánica, 52 (suplemento), p. 344-345. In northern Argentina and Bolivia, theMacharetí, Mandiyutí (Pennsylvanian)and Cuevo (Permian) and Titicaca(Pennsylvanian Permian) groups containvariable frequencies of spores and pollengrains (monosaccate, bisaccate and taeniate)spanning this interval. The Pennsylvanian unitsin northern Argentina and southern Boliviaare dominated by non striate/taeniate (ST)monosaccate and less bisaccate pollen grainsgenerally of cordaitalean and coniferaleanafÞ nities, but with signiÞ cant contributionsfrom lower vascular plants, notablypteridophytes, sphenophylls and lycopodsand very scarce ST pollen grains representingpteridosperms. Whereas, in units of centralnorthern Bolivia, several ST bisaccatepollen grains mainly of Protohaploxypinus-Stri at oabi eit es-St riat opodocarpidi te sgenera belonging to Pteridosperms are morefrequent. This would imply seasonal climatesunder humid conditions for the former ß oraswith respect to the other assemblages withST pollen grains attesting seasonal climatesunder drier conditions. In the Cisuralian, theever-present ST taxa of typical genera such asVittatina, Lueckisporites, Hamiapollenites,Lunatisporites, Pakhapites, Illinites, amongothers, registered in all the assemblages of thementioned units are related to the incomingof glossopterids and other gymnospermicplant groups during the Permian that wouldattest general warmer climates provedby the Gondwana movement to lowerlatitudes. Differences in Þ rst appearanceof same taxa (diachronism) are explainedbased on migration of plant species andpunctuated changes in paleogeography andclimate affected by near-field glaciation anddeglaciation processes. These ß oral changesare similar to other basins of South Americaand were useful to establish biozonalcorrelations and improve paleobiogeographicdistribution of the FLoras throughoutGondwana and elsewhere.