Cebollati group, Nico Perez terrane: Definition and age; Grupo Cebollati, terreno Nico Perez: Definicion y edad

The Cebollati Group (Nico Perez Terrane) is formally erected in this work to include a meta sedimentary succession informally known as {sup L}as Teta s Complex{sup .} It is shown that the stratigraphy of the unit can be reconstructed at a number of sections between Minas and Zapicin, using sedimentary structures and stromatolites as geo petal indicators. The basement of the group is represented by metamorphic rocks and granitoids of the La China Complex, for which a new U-Pb zircon age of 3.029 ± 54 Ma is presented. The Cebollatii Group comprises, from base to top, three formations: the Arroyo Ma lo Formation (sandstones and petites), Cerro de Valuable Formation (dolostones, partly stromatolitic, and p elites) and the Cerro del Diamant e Formation (p elites, BIF, quartz-pebble conglomerates and sandstones). The mean thickness of the Cebollatii Group is ca. 2 km, being greatest in the south and diminishing to the north. Available ages for the unit suggested a Neoarchean depositional age of 2.75 Ga. However, in this work 12 Nd model ages are presented for sedimentary rocks of the Cebollati Group, which are mostly younger than 2.75 Ga, the youngest being 1.64 Ga. These ages call into question the Neoarchean age accepted for the unit, suggesting a Meso proterozoic depositional age. The evidence supporting both views is discussed in view of the new data. The minimum age of the Cebollati Group is 1.3 Ga on the basis of carbon isotope ratios of dolostones and deformational ages consistently around 1.25 Ga.