Carboniferous postglacial brachiopod faunas in the Southwestern Gondwana margin

CISTERNA, G.A.; STERREN, A.F.

Nanjing

Congreso; 7th International Brachiopod Congress; 2015

The glaciomarine sediments related to the Late Paleozoic Ice Age (LPIA),have an excellent stratigraphic record in Argentina, particular thoseassociated to the Late Carboniferous glacial episode identified along thesouthwestern South American basins. The deglaciation processes connected tothis event produced an important sea level rise and consequently an extended postglacialtransgression from Bolivia (Tarija basin) to Argentina (Precordillera andPatagonia). Two postglacial faunas associated to the diamictite bearing sequencesof the late Serpukhovian-Bashkirian interval are recognized: the widelyextended Levipustula fauna identifiedin the Argentine Precordillera and Bolivia, and the Aseptella-Tuberculatella/Rhipidomella-Micrapheliaassociation from Precordillera. Strong faunal contrasts between westernArgentina and Patagonia have been proposed because of the paleogeographicalposition of Patagonia, considered to be a terrane accreted to Gondwana in theLate Paleozoic (Ramos, 2008).  However, theLanipustula fauna dominated bybryozoans and bivalves with diversified spiriferid brachiopods appears to becomparable with the Levipustula faunafrom western Argentina. Also, the brachiopod assemblage from Tuberculatella biozone would exhibit somecommon elements (Tuberculatella,Aseptella, Beecheria) with the Aseptella-Tuberculatella/Rhipidomella-Micraphelia association, henceit could have also an interbasinal correlation value. The significant compositionaldifferences observed between this assemblage and the relatively equivalent Levipustula fauna, should be explainedby paleoecological controls. The present review offers an appropriated scenarioto future statistics paleoecological analyzes, with the purpose of tounderstand the evolution of the Carboniferous postglacial faunas in Gondwana.