Provenance studies on Neoproterozoic successions of the Tandilia System (Buenos Aires province, Argentina): Preliminary data

UDO ZIMMERMANN, DANIEL POIRÉ AND LUCÍA GÓMEZ PERAL

La Plata, Argentina

Congreso; XVI Congreso Geológico Argentino; 2005

Asociación Geológica Argentina

Neoproterozoic successions in the Tandilia System are well understood regarding petrography and facies. However, the exact age constraint and the tectonic setting are not well known. This study likes to decipher the composition of the source areas and using an integrated provenance study to understand the evolution of the Sierras Bayas basin using the sedimentary successions of the Sierras Bayas Group and the Cerro Negro Formation, which are covering a Paleoproterozoic basement comprised mainly of granitoids, orthogneisses and migmatites. Occurring major unconformities can be interpreted as basin wide and could lead to the understanding of a probable change in provenance, as a change in facies as well in mineralogical composition is observable. In contrast to comparable Neoproterozoic deposits in Uruguay, Africa significant differences are observable. The rocks in the Tandilia System are unfolded, unmetamorphosed, well preserved including the carbonate sequences, comprising no pronounced glacial deposits and no glacial related primary C-O isotope signature. The rocks are not penetrated by magmatic events with the exception of the Los Barrientos basic dolerites. Especially the fact that the rocks are not affected by any defined regional tectonic episode, a rifting around 740 Ma, or a collisional event around 540 Ma makes this succession unique. Finally, the well-preserved strata and the well understood stratigraphy are perfect preconditions to perform geochemical studies, as detailed C-O isotope analyses could reveal.