Provenance and paleogeography of the Devonian Durazno Group, southern Parana Basin in Uruguay

BASEI MIGUEL ANGELO STIPP; SICCARDI ARON; URIZ NORBERTO J.; BLANCO GONZALO; CINGOLANI CARLOS A.; ABRE PAULINA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 66 p. 248 - 267

0895-9811

A succession of Devonian cover rocks occurs in outcrop and in the subsurface of central-northernUruguay where they were deposited in an intracratonic basin. This Durazno Group comprises threedistinct stratigraphic units, namely the Cerrezuelo, Cordob es and La Paloma formations. The Durazno Group does not exceed 300 m of average thickness and preserves a transgressive-regressive cycle within a shallow-marine siliciclastic shelf platform, and is characterized by an assemblage of invertebrate fossils of Malvinokaffric affinity especially within the Lower Devonian Cordob es shales. The sedimentary provenance of the Durazno Group was determined using petrography, geochemistry, and morphological studies of detrital zircons as well as their UePb ages. Sandstone petrography of Cerrezuelo and La Paloma sequences shows that they have a dominantly quartz-feldspathic composition with a minor contribution of other minerals. Whole-rock geochemical data indicate that alteration was strong in each of the three formations studied; chondritic-normalized REE patterns essentially parallel to PAAS, the presence of a negative Eu-anomaly, and Th/Sc and La/Hf ratios point to an average source composition similar to UCCor slightly more felsic. Within the Cerrezuelo Formation, recycling of older volcano-etasedimentarysources is interpreted from Zr/Sc ratios and high Hf, Zr, and REE concentrations. UePb detrital zircon age populations of the Cerrezuelo and La Paloma formations indicate that the principal source terranes are of Neoproterozoic age, but include also minor populations derived from Mesoproterozoic and Archean-Paleoproterozoic rocks. A provenance from the Cuchilla Dionisio-Dom Feliciano, Nico P erez and Piedra Alta terranes of Uruguay and southern Brazil is likely. This study establishes an intracratonic extensional tectonic setting during Durazno time. Considering provenance age sources, regional paleocurrent distributions and the established orogenic history recorded in SW Gondwana, we suggest that the basinfill was derived from paleohighs located in what is currently SE Uruguay.