MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The evolution of floristic diversity in western Gondwana during the Late Paleozoic: A palynological approach
Autor/es:
BALARINO, M.L.; BERI, Á.; GUTIÉRREZ, P.R.
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress. The History of Life: A view from the Southern Hemisphere; 2014
Resumen:
This work analyzed the evolution of palynological assemblage diversity using the number of the genera present in each sample. Samples from two boreholes from the Paraná Basin, Uruguay (26 samples of DI.NA.MI.GE. Paso de las Toscas N° 254 and 14 samples of DI.NA.MI.GE. Cerrillada N° 221), one borehole from the Claromecó Basin, Argentina (10 samples of UTAL.La Estrella.x-1) and 18 outcrop samples from the La Deheza Formation, Paganzo Basin, Argentina, were analyzed. All analyses were performed with PAST 2.16. The evolution of diversity, extinction and appearance curves for each analyzed unit were obtained. In the boreholes 254 and 221, the biozones Cristatisporites inconstans-Vittatina saccata (early Cisuralian) and Striatoabieites anaverrucosus-Sataurosaccites cordubensis (late Cisuralian ? early Guadalupian) were recognized. In the La Deheza Formation, the biozones Raistrickia densa-Convolutispora muriornata (late Mississippian-Pennsylvanian), Pakhapites fusus-Vittatina subsaccata (late Pennsylvanian- early Cisuralian) and Lueckisporites-Weylandites (late Cisuralian- early Guadalupian) were recognized. The last two biozones can be partially correlated with those proposed in the Uruguayan boreholes. In the borehole La Estrella, the biozones Converrucosiporites confluens-Vittatina vittifera (early Cisuralian) and Tornopollenites toreutos-Reduviasporonites chalastus (late Cisuralian - Guadalupian) were recognized. The microfloristic assemblages from 221 and 254 boreholes and the La Deheza Formation show a similar diversity trend. An increase in diversity is observed at the basal section of each biozone and a steady diversity decrease towards their younger horizons. The genera appearance tends to be more important in the lowermost stratigraphic levels of each biozone. The extinction rates are predominant in the younger biozones. It is possible to observe that richness trends throughout the interval analyzed herein correlate with sedimentary facies that, in fact, are related to climatic changes. The pattern of palynofloral diversity evolution in boreholes 254, 221 and the La Deheza Formation indicates an increase of richness in glacial, glaciofluvial and deltaic environments with coal deposits. In lagoonal facies a peak of diversity first occurs, followed by a steady increase in extinction rates and scarce genera appearance. This process of extinction becomes more important in shallow marine facies.