MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Eifelian-Givetian diversity trends in palynofloras from northwestern Argentian
Autor/es:
SOL NOETINGER; MERCEDES DI PASQUO
Lugar:
Mendoza
Reunión:
Congreso; 4th International Paleontological Congress; 2014
Institución organizadora:
IANIGLA
Resumen:
This study aims to elucidate diversity trends during the Middle Devonian in northwestern Argentina
through the characterization of palynological events. A dataset of spore genera counts from two
boreholes (San Antonio x-1, Santa Victoria x-1), ranging in age from the Eifelian to Givetian, was
analyzed. Several measures of diversity were compiled and contrasted with the composition of
the floras. The Simpson, Shannon-Wiener and standing diversity indices together with Pielou
and Hurlburt?s evenness measures were calculated. The standing diversity reaches its maximum
during the Eifelian and rapidly decreases towards the Givetian. This tendency is also supported by
the other computed parameters. The floras, during the Eifelian, are composed of apiculate, cavate
and boldly sculptured spores represented mainly by the genera Apiculiretusispora, Grandispora
and Verrucosisporites respectively. The decline in the evenness, towards the top of the sections, is
shown when the Verrucosisporites genus outnumbers in the assemblages. The domination of these
specimens is a pattern seen in other parts of Gondwana during the same time frame. The increment
of this particular genus, associated with filicopsids, co-occurs with the inception of Geminospora
lemurata and Biharisporites parviornatus. These species have a well-defined onset worldwide during
the late Eifelian?early Givetian and are known to have affinities with archaeopteridaleans. Both,
marine and continental elements, sustain a marginal depositional setting, with minor shoreline
shifts for both assemblages during the Eifelian. By the early Givetian there is a significant increase
of marine components. The diversity analysis and inferred palaeoenvironment support a change in
the conditions, that show a stressed domain during the late Eifelian?early Givetian, which led to the
predominance of few existing species and the establishment of new ones in the flora.